Essential Oils: Extraction, Bioactivities, and Their Uses for Food Preservation

Essential Oils: Extraction, Bioactivities, and Their Uses for Food Preservation
R: Concise Reviews
                                                                                                                                                              in Food Science
Essential Oils: Extraction, Bioactivities, and Their
Uses for Food Preservation
Phakawat Tongnuanchan and Soottawat Benjakul

    Abstract:    Essential oils are concentrated liquids of complex mixtures of volatile compounds and can be extracted from
    several plant organs. Essential oils are a good source of several bioactive compounds, which possess antioxidative and
    antimicrobial properties. In addition, some essential oils have been used as medicine. Furthermore, the uses of essential oils
    have received increasing attention as the natural additives for the shelf-life extension of food products, due to the risk in
    using synthetic preservatives. Essential oils can be incorporated into packaging, in which they can provide multifunctions
    termed “active or smart packaging.” Those essential oils are able to modify the matrix of packaging materials, thereby
    rendering the improved properties. This review covers up-to-date literatures on essential oils including sources, chemical
    composition, extraction methods, bioactivities, and their applications, particularly with the emphasis on preservation and
    the shelf-life extension of food products.

    Keywords: antimicrobial, antioxidant, biodegradable film, essential oil, food product, volatile compound

Introduction                                                                      Sources and Chemical Composition
   Essential oils, also called volatile odoriferous oil, are aromatic                Several plants contain essential oils, however, parts of plants,
oily liquids extracted from different parts of plants, for example,               which serve as the major source of essential oil can be different
leaves, peels, barks, flowers, buds, seeds, and so on. They can be                (Table 1). Those include roots, peels, leaves, seeds, fruits, barks, and
extracted from plant materials by several methods, steam distil-                  so on. Plant essential oils are usually the complex mixture of nat-
lation, expression, and so on. Among all methods, for example,                    ural compounds, both polar and nonpolar compounds (Masango
steam distillation method has been widely used, especially for                    2005). Dominant compounds in various essential oils are pre-
commercial scale production (Cassel and Vargas 2006; Di Leo Lira                  sented in Table 2. In general, the constituents in essential oils are
and others 2009). Essential oils have been widely used as food                    terpenes (monoterpenes and sesquerpenes), aromatic compounds
flavors (Burt 2004). Essential oils found in many different plants,               (aldehyde, alcohol, phenol, methoxy derivative, and so on), and
especially the aromatic plants, vary in odor and flavor, which are                terpenoids (isoprenoids) (Bakkali and others 2008; Mohamed and
governed by the types and amount of constituents present in oils.                 others 2010). Compounds and aroma of essential oils can be di-
Additionally, the amount of essential oil from different plants is                vided into 2 major groups: terpene hydrocarbons and oxygenated
different and this determines the price of essential oil. Apart from              compounds.
aromatic compounds, indigenous pigments contribute to varying
colors of essential oil. This can affect the applications as the in-              Terpene hydrocarbons
gredient in some particular foods. Essential oils have been known                    The hydrocarbons are the molecule, constituting of H and C
to possess antioxidant and antimicrobial activities, thereby serving              atoms arranged in chains. These hydrocarbons may be acyclic, al-
as natural additives in foods and food products. It can be used as                icyclic (monocyclic, bicyclic, or tricyclic), or aromatic. Terpenes
active compounds in packaging materials, in which the proper-                     are the most common class of chemical compounds found in essen-
ties of those materials, particularly water vapor barrier property                tial oils. Terpenes are made from isoprene units (several 5 carbon
associated with hydrophobicity in nature of essential oils, can be                base units, C5 ), which are the combinations of 2 isoprene units,
improved. Almost any part of a plant may be the source of the oil,                called a “terpene unit.” Essential oils consist of mainly monoter-
which could be extracted and fully exploited for food applications                penes (C10 ) and sesquiterpenes (C15 ), which are hydrocarbons
or others. Modern technologies have been continuously devel-                      with the general formula (C5 H8 )n . The diterpenes (C20 ), triter-
oped to conquer the limitation of conventional methods, and to                    penes (C30 ), and tetraterpenes (C40 ) exist in essential oils at low
enhance the extraction efficacy. Due to the increasing attention                  concentration (Mohamed and others 2010). Terpenoids (a terpene
in natural additives, essential oils from several plants have been                containing oxygen) is also found in essential oils (Burt 2004).
used more widely, especially in conjunction with other preserva-                     Essential oils mostly contain monoterpenes and sesquiterpenes,
tions under concept of “hurdle technology.” Thus, essential oils                  which are C10 H16 (MW 136 amu) and C15 H24 (MW 204 amu), re-
can serve as the alternative additives or processing aid as green                 spectively. Although sesquiterpenes are larger in molecules, struc-
technology.                                                                       ture and functional properties of sesquiterpenes are similar to
                                                                                  the monoterpenes (Ruberto and Baratta 2000). For diterpenes,
                                                                                  triterpenes, and tetraterpenes, they have the larger molecule than
                                                                                  monoterpenes and sesquiterpenes, but they are present at very low
                                                                                  concentration in essential oils (Bakkali and others 2008).
MS 20131520 Submitted 10/23/2013, Accepted 4/9/2014. Authors are with
Dept. of Food Technology, Faculty of Agro-Industry, Prince of Songkla Univ., 15
Kanchanawanish Road, Hat Yai, Songkhla, 90112, Thailand. Direct inquiries to      Oxygenated compounds
author Benjakul (E-mail:                                    These compounds are the combination of C, H, and O,
                                                                                  and there are a variety of compounds found in essential oils.

C 2014 Institute of Food Technologists

doi: 10.1111/1750-3841.12492                                                                  Vol. 79, Nr. 7, 2014 r Journal of Food Science R1231
Further reproduction without permission is prohibited
Essential Oils: Extraction, Bioactivities, and Their Uses for Food Preservation
R: Concise Reviews   Bioactivities and applications of essential oils . . .
 in Food Science

                     Table 1–Parts of plant material containing essential oils.

                     Parts                                                                               Plants
                     Leaves                Basil, bay leaf, cinnamon, common sage, eucalyptus, lemon grass, citronella, melaleuca, mint, oregano, patchouli, peppermint, pine,
                                             rosemary, spearmint, tea tree, thyme, wintergreen, kaffir lime, laurel, savory, tarragon, cajuput, lantana, lemon myrtle, lemon
                                             teatree, niaouli, may chang, petitgrain, laurel, cypress
                     Seeds                 Almond, anise, cardamom, caraway, carrot celery, coriander, cumin, nutmeg, parsley, fennel
                     Wood                  Amyris, atlas cedarwood, himalayan cedarwood, camphor, rosewood, sandalwood, myrtle, guaiac wood
                     Bark                  Cassia, cinnamon, sassafras, katrafay
                     Berries               Allspice, juniper
                     Resin                 Frankincense, myrrh
                     Flowers               Blue tansy, chamomile, clary sage, clove, cumin, geranium, helichrysum hyssop, jasmine, lavender, manuka, marjoram, orange, rose,
                                             baccharises, palmarosa, patchouli, rhododendron anthopogon, rosalina, ajowan, ylang-ylang, marjoram sylvestris, tarragon,
                                             immortelle, neroli
                     Peel                  Bergamot, grapefruit, kaffir lime, lemon, lime, orange, tangerine, mandarin
                     Root                  Ginger, plai, turmeric, valerian, vetiver, spikenard, angelica
                     Fruits                Xanthoxylum, nutmeg, black pepper

                     Oxygenated compounds can be derived from the terpenes, in 1992). The proportion of essential oils extracted by steam distilla-
                     which they are termed “terpenoids.” Some oxygenated com- tion is 93% and the remaining 7% can be further extracted by other
                     pounds prevalent in plant essential oils are shown as follows:          methods (Masango 2005). Basically, the plant sample is placed in
                                                                                             boiling water or heated by steam (Figure 1). The heat applied is
                     - Phenols: thymol, eugenol, carvacrol, chavicol, thymol, and so on. the main cause of burst and break down of cell structure of plant
                     - Alcohols:                                                             material. As a consequence, the aromatic compounds or essential
                     Monoterpene alcohol: borneol, isopulegol, lavanduol, α- oils from plant material are released (Perineau and others 1992;
                       terpineol, and so on.                                                 Babu and Kaul 2005). The temperature of heating must be enough
                     Sesquiterpenes alcohol: elemol, nerolidol, santalol, α-santalol, and to break down the plant material and release aromatic compound
                       so on.                                                                or essential oil. A new process design and operation for steam
                                                                                             distillation of essential oils to increase oil yield and reduce the
                     - Aldehydes: citral, myrtenal, cuminaldehyde, citronellal, cin- loss of polar compounds in wastewater was developed by Masango
                       namaldehyde, benzaldehyde, and so on.                                 (2005). The system consists of a packed bed of the plant materi-
                     - Ketones: carvone, menthone, pulegone, fenchone, camphor, thu- als, which sits above the steam source. Only steam passes through
                       jone, verbenone, and so on.                                           it and the boiling water is not mixed with plant material. Thus,
                     - Esters: bomyl acetate, linalyl acetate, citronellyl acetate, geranyl the process requires the minimum amount of steam in the process
                       acetate, and so on.                                                   and the amount of water in the distillate is reduced. Also, water-
                     - Oxides: 1,8-cineole, bisabolone oxide, linalool oxide, sclareol soluble compounds are dissolved into the aqueous fraction of the
                       oxide, and so on.                                                     condensate at a lower extent (Masango 2005). Yildirim and others
                     - Lactones: bergaptene, nepetalactone, psoralen, aesculatine, cit- (2004) reported that the 2,2-diphenyl-1-picryl hydrazyl (DPPH)
                       roptene, and so on.                                                   radical scavenging activities of essential oils from steam distillation
                     - Ethers: 1,8-cineole, anethole, elemicin, myristicin, and so on.       process were markedly higher than those of oils extracted using
                                                                                             hydrodistillation (HD).
                        Different constituents in essential oils exhibit varying smell or
                     flavor (Burt 2004). Also, the perception of individual volatile com-       Hydrodistillation. HD has become the standard method of
                     pounds depends on their threshold.                                      essential oil extraction from plant material such as wood or flower,
                                                                                             which is often used to isolate nonwater-soluble natural products
                                                                                             with high boiling point. The process involves the complete immer-
                     Extraction of Essential Oils                                            sion of plant materials in water, followed by boiling. This method
                        Essential oils can be extracted from several plants with differ- protects the oils extracted to a certain degree since the surround-
                     ent parts by various extraction methods. The manufacturing of ing water acts as a barrier to prevent it from overheating. The
                     essential oils, and the method used for essential oil extraction are steam and essential oil vapor are condensed to an aqueous fraction
                     normally dependent on botanical material used. State and form (Figure 2). The advantage of this technique is that the required
                     of material is another factor used for consideration. Extraction material can be distilled at a temperature below 100 °C. Okoh
                     method is one of prime factors that determine the quality of and others (2010) studied the different extraction processes on
                     essential oil. Inappropriate extraction procedure can lead to the yield and properties of essential oil from rosemary (Rosmarinus of-
                     damage or alter action of chemical signature of essential oil. This ficinalis L.) by HD and solvent-free microwave extraction (SFME).
                     results in the loss in bioactivity and natural characteristics. For se- The total yields of the volatile fractions obtained through HD
                     vere case, discoloration, off-odor/flavor as well as physical change and SFME were 0.31% and 0.39%, respectively. HD oil contained
                     such as the increased viscosity can occur. Those changes in ex- more monoterpene hydrocarbons (32.95%) than SFME-extracted
                     tracted essential oil must be avoided. Extraction of essential oils oil (25.77%), while higher amounts of oxygenated monoterpenes
                     can be carried out by various means, as shown in Table 3.               (28.6%) were present in the oil extracted by SFME in compar-
                                                                                             ison with HD (26.98%). Golmakani and Rezaei (2008) studied
                     Distillation                                                            the microwave-assisted HD (MAHD), which is an advanced HD
                        Steam distillation. Steam distillation is the most widely used technique utilizing a microwave oven in the extraction process.
                     method for plant essential oil extraction (Reverchon and Senatore MAHD was superior in terms of saving energy and extraction time

                     R1232 Journal of Food Science r Vol. 79, Nr. 7, 2014
Essential Oils: Extraction, Bioactivities, and Their Uses for Food Preservation
Table 2–Major compounds in different plant essential oils.
                                                                                         Monoterpene                  Oxygenated                      Sesquiterpene                  Oxygenated
                                                       Essential oils                    hydrocarbons                monoterpenes                     hydrocarbons                  sesquiterpenes                  Esters                     Others                          References
                                                       Basil                      β-Pinene, β-Limonene,       endo-5,5,6-Trimethyl-2-        β-Elemene, 2,6-Dimethyl-6-      Methyleugenol                   –                     Methylchavicol,3-                  Teixeira and others (2013)
                                                                                    γ -Terpinene                norbornanone                    (4-methyl-3-pentenyl)-                                                              Methoxycinnamaldehyde
                                                                                                                                                γ -Cadinene, γ -Muurolene
                                                       Citronella                 S-3-Carene,                 (−)-Isopulegol, β-Citronellal, β-Elemene, β-Selinene,          (−)-Cedreanol                   m-(Trimethylsiloxy)   -                                  Teixeira and others (2013)
                                                                                    Mentha-1,4,8-triene,         β- Citronellol                 α-Selinene, α-Muurolene,                                       -cinnamic acid
                                                                                    2 -Carene, cis-2,6-                                        (+)-δ-Cadinene,                                                methyl ester
                                                                                    Dimethyl-2,6octadiene,                                      Eremophilene, γ -Selinene,
                                                                                    γ -Terpinene                                                (+)-δ-Selinene,
                                                       Clove                      –                           –                              trans-Caryophyllene,            Methyleugenol                   Aceteugenol           p-Eugenol                          Teixeira and others (2013)
                                                       Garlic                     1(7),5,8-o-Menthatriene     trans-Limone oxide,            –                               –                               –                     di-2-Propenyldisulfide,            Teixeira and others (2013)
                                                                                                                 endo-5,5,6-Trimethyl-2-                                                                                              Dimethyl tetrasulphide, di-
                                                                                                                 norbornanone,                                                                                                        2-Propenyltetrasulfide,3,3 -
                                                                                                                                                                                                                                                                                                       Bioactivities and applications of essential oils . . .

                                                       Lemon                      α-Pinene, β-Pinene,         –                                trans-Caryophyllene           –                               –                     1,2,3,5-Tetramethyl-               Teixeira and others (2013)
                                                                                    Cymene, α-Limonene,                                                                                                                               benzene,1-(1,5-
                                                                                    α-Fellandrene                                                                                                                                     Dimethylhexyl)-4-
                                                       Lemon                      α-Pinene, α-Fenchene,       Citronellal, cis-Carveol,        –                             –                               –                     Cyclohexane, Heptanal,             Mohamed and others (2010)
                                                                                    Limonene, Camphene          α-Citral, Carvacol,                                                                                                   Dihydroiso-pimaric,
                                                                                                                Terpniol,                                                                                                             Dihydro-abitec
                                                                                                                Thymol, Carvacrol, Citral
                                                       Lemongrass                 α-Pinene, 3-Carene,         β-Citral, α-Citral,              β-Caryophyllene               –                               –                     m-Eugenol, Geranyl                 Leimann and others (2009)
                                                                                    Camphene                    α-Cyclocitral,                                                                                                       N-butyrate, Isogeraniol
                                                       Mandarin                   α-Pinene, di-Limonene,      Neo-Dihydrocaveol,               Farnesene, α-Farnesene        –                               –                     Linalyl acetate, Undecanoic        Mohamed and others (2010)
                                                                                    Allo-Ocimene,               cis-Limonene oxide,                                                                                                  acid, Methly-anthranilate,
                                                                                    Camphene, Sabinene          Linalool, Borneol,                                                                                                   Benzaldehyde
                                                       Mint(Saturejacuneifolia)   α-Pinene, Myrcene,          Thymol, Carvacrol,               β-Bourbonene,                 Caryophyllene oxide,            –                     –                                  Bezić and others (2005)
                                                                                    Limonene, cisβ-Ocimene,     Camphor, Linalool,               β-Caryophyllene,              aSpathulenol, Viridiflorol,
                                                                                    p-Cymene, allo-Ocimene      Terpinen-4-ol, Neral,            Aromadendrene,
                                                                                                                α-Terpineol, Borneol,            β-Cubebene, δ-Cadinene,
                                                                                                                Geranial, Geraniol
                                                       Mintb(Satureja montana)    α-Thujene, α-Pinene,        Linalool, α-Terpineol,           β-Cubebene, δ-Cadinene        Caryophyllene oxide,            –                     1-Octen-3-ol, Thymol               Bezić and others (2005)
                                                                                    Myrcene, α-Terpinene,       Borneol,                                                       Spathulenol                                           methylether, Carvacrol
                                                                                    γ -Terpinene, p-Cymene      Thymol, Carvacrol                                                                                                    methyl ether, Thymyl
                                                       Orange                     Myrcene, β-Phellandrene,    cis-Limoneneoxide, Decanal,      Farnesene                     –                               –                     Nonyl-aldehyde, Caprylic           Mohamed and others (2010)
                                                                                   α-Terpinolene,                Linalool,                                                                                                           acid, Cinnamic-aldehyde,
                                                                                   Menthatriene                  Verbenol, Carvone,                                                                                                  Heptadecanol
                                                                                                                 Perilladehyde, cis-Carveol,

Vol. 79, Nr. 7, 2014 r Journal of Food Science R1233
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Essential Oils: Extraction, Bioactivities, and Their Uses for Food Preservation
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                                                                                                                                                                                                                                                                               R: Concise Reviews

                                                       Table 2–Continued.
                                                                                           Monoterpene                       Oxygenated                   Sesquiterpene                  Oxygenated
                                                       Essential oils                      hydrocarbons                     monoterpenes                  hydrocarbons                  sesquiterpenes             Esters                  Others                      References
                                                       Oregano                     α-Terpinene,                      1,8-Cineole, Terpinen-4        β-Caryophyllene, cis-Hydrate –                          –                   –                             Aguirre and others (2013)
                                                                                     Limonene, γ -Terpinene             -ol, α-Terpineol, Thymol,     sabinene, trans-Hydrate
                                                                                                                        Carvacrol,                    sabinene
                                                       Plai-Dam (Zingiber          α-Pinene, β-Pinene,               1,8-Cineole, Linalool,         β-Elemene, β-Caryophyllene, Caryophyllene oxide,        –                   Bornyl acetate, Sabinene      Thubthimthed and others
                                                         ottensii)                   Sabinene, Myrcene,                 Terpinen-4-ol,                Humulene                     Humulene oxide,                                hydrate,                      (2005)
                                                                                     α-Terpinene, Limonene,             cis-Menth-2-en-1-ol,                                       α-Eudesimol,                                   4-phenylbutan-2-one
                                                                                     E-β-Ocimene, p-Cymene,             Borneol, trans-Piperitol                                   β-Eudesimol, Zerumbone
                                                                                     γ -Terpinene
                                                       Rosemary                    α-Pinene, Camphene,               Eucalyptol,                    trans-Caryophyllene           –                         (−)-Bornylacetate   –                             Teixeira and others (2013)

R1234 Journal of Food Science r Vol. 79, Nr. 7, 2014
                                                                                     β-Pinene, Cymene,                 (E)-2,3-Epoxycarane,(−)-
                                                                                                                                                                                                                                                                                             Bioactivities and applications of essential oils . . .

                                                                                     α-Fellandrene, S-3-Carene,        Camphor, endo-Borneol,
                                                                                     m-Cymene,                         endo-5,5,6-Trimethyl-2-
                                                                                     Mentha-1,4,8-triene               norbornanone
                                                       Sage                        α-Pinene, Camphene,               Eucalyptol,                    trans-Caryophyllene,          –                         (−)-Bornylacetate   –                             Teixeira and others (2013)
                                                                                     β-Pinene, Cymene,                 (E)-2,3-Epoxycarane,(−)-        β-Selinene, β-Bisabolene
                                                                                     α-Fellandrene, m-Cymene,          Camphor, endo-Borneol,
                                                                                     Mentha-1,4,8-triene,              endo-5,5,6-Trimethyl-2-
                                                                                     2 -Carene,1,3,8-p-               norbornanone
                                                       Tangerine                   α-Pinene, Limonene,               Citronellal, Linalool,         –                             Ledol, Globulol           –                   Aloxiprin, Heptadiene,        Mohamed and others (2010)
                                                                                     α-Terpinene, trans-               cis-Limonene oxide,                                                                                        Methyl- heptadiene,
                                                                                     Menthadiene,                      trans-Carveol, Limonene                                                                                    Cyclooctanone, Benzyl-
                                                                                     trans-Ocimene,                    dioxide, Perillyl alcohol                                                                                  dicarboxylic
                                                       Thyme                       Camphene, β-Pinene,               Eucalyptol,                    trans-Caryophyllene           –                         –                   (3E,5E,8E)-3,7,11-Trimethyl- Teixeira and others (2013)
                                                                                     Cymene, α-Fellandrene,            (E)-2,3-Epoxycarane,                                                                                       1,3,5,8,10-dodecapentaene
                                                                                     m-Cymene                          endo-5,5,6-Trimethyl-m-
                                                       Thymus longicaulis subsp.      α-Thujene, α-Pinene,           Camphor, Borneol,              α-Humulene, δ-Cadinene,       –                         –                   –                             Sarikurkcu and others (2010)
                                                         longicaulis var. longicaulis   Myrcene, Camphene,             Terpinen-4-ol,                 Germacrene D
                                                                                        β-Pinene, α-Phellandrene,      α-Terpineol,
                                                                                        α-Terpinene, p-Cymene,         Thymol, Carvacrol,
                                                                                        (E)- β-Ocimene,                β-Caryophyllene
                                                                                        γ -Terpinene, cis-Sabinene
                                                                                        hydrate, Terpinolene
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Bioactivities and applications of essential oils . . .

                                                                                                                                                                      in Food Science
Table 3–Extraction of essential oils from various sources using several methods.

Extraction methods                                              Plants                                                          References
Solvent extraction – Solvent   sage (Salvia officinalis), apiaceae (Ptychotis verticillata), chasteberry   Durling and others (2007); Matsingou and others (2003);
                                  (Vitexagnuscastus L.), lemon (Citrus x limon)                              El Ouariachi and others (2011); Sarikurkcu and others
                                                                                                             (2009); Koshima and others (2012)
– Supercritical CO2            rosemary (Rosmarinus officinalis), fennel (Foeniculum vulgare), anise       Pereira and Meireles (2007); Reverchon and Senatore
                                  (Pimpinella anisum), cumin seed (Cuminum cyminum), sage                    (1992); Eikani and others (1999); Djarmati and others
                                  (Salvia officinalis), lemon (Citrus x limon), carrot fruit (Daucus         (1991); Gironi and Maschietti (2008); Glišić and
                                  carrota L.), marjoram (Majorana hortensis Moench), catnip                  others (2007); Dapkevicius and others (1998);
                                  (Nepeta cataria L.), oregano (Origanum vulgare L.), lavender               Donelian and others (2009); Li and others (2009);
                                  (Lavandula angustifolia Mill), thyme (Thymus vulgaris L.),                 Guan and others (2007); Mhemdi and others (2011);
                                  hyssop (Hyssopus officinalis L.), anise hyssop (Lophantus anisatus         Araus and others (2009); Xavier and others (2011)
                                  Benth), patchouli (Pogostemon cablin), cumin (Cuminum
                                  cyminum), clove (Eugenia caryophyllata), coriander (Coriandrum
                                  sativum L.), chamomile (Matricaria chamomilla), baccharises
                                  (Baccharis uncinella, Baccharis anomala, and Baccharis dentata)
– Subcritical water            fructus amomi, marjoram (Origanum majorana), olive (Olea                    Deng and others (2005); Jimenez-Carmona and others
                                  europaea), coriander seeds (Coriandrum sativum L.)                         (1999); Amarni and Kadi (2010); Eikani and others
Distillation - Steam           rose-scented geranium (Pelargonium sp.), thyme (Thymus                      Babu and Kaul (2005); Sefidkon and others (1999);
                                  kotschyanus), germander (Teucrium orientale), rosemary                     Yildirim and others (2004); Pereira and Meireles
                                  (Rosmarinus officinalis), fennel (Foeniculum vulgare), anise               (2007); Rajeswara Rao and others (2003); Cassel and
                                  (Pimpinella anisum), eucalyptus (Eucalyptus citriodora), basil             others (2009); Donelian and others (2009); Guan and
                                  (Ocimum basilicum L.), lavender (Lavandula dentata L.),                    others (2007); Farhat and others (2011)
                                  patchouli (Pogostemon cablin), clove (Eugenia caryophyllata),
                                  orange (Citrus sinensis)
– Hydrodistillation            rose-scented geranium (Pelargonium sp.), germander (Teucrium                Babu and Kaul (2005); Yildirim and others (2004);
                                  orientale), rosemary (Rosmarinus officinalis), lemon (Citrus x             Reverchon and Senatore (1992); Ferhat and others
                                  limon), oregano (Origanum vulgare L.), marjoram (Majorana                  (2007); Bayramoglu and others (2008); Dapkevicius
                                  hortensis Moench), catnip (Nepeta cataria L), lavender                     and others (1998); Li and others (2009); Guan and
                                  (Lavandula angustifolia Mill), hyssop (Hyssopus officinalis L.),           others (2007); Farhat and others (2010); Gavahian and
                                  anise hyssop (Lophantus anisatus Benth), sage (Salvia officinalis          others (2012)
                                  L), cumin (Cuminum cyminum), clove (Eugenia caryophyllata),
                                  caraway (Carum carvi), thyme (Thymus vulgaris L.), basil
                                  (Ocimum basilicum L.), garden mint (Mentha crispa L.)
– Hydrodiffusion               orange (Citrus sinensis), rosemary leaves (Rosmarinus officinalis)          Farhat and others (2011); Bousbia and others (2009)
Solvent-free microwave         oregano (Origanum vulgare L.), fragrant fern (Dryopteris fragrans),         Bayramoglu and others (2008); Li and others (2012);
                                  rosemary (Rosmarinus officinalis), caraway (Carum carvi), 5                Okoh and others (2010); Farhat and others (2010); Ma
                                  flavor berry (Schisandra chinensis), cumin (Cuminum cyminum                and others (2012); Wang and others (2006); Lucchesi
                                  L.), cardamom (Elletaria cardamomum L.), basil (Ocimum                     and others (2007); Lucchesi and others (2004); Michel
                                  basilicum L.), garden mint (Mentha crispa L.), thyme (Thymus               and others (2011); Vian and others (2008)
                                  vulgaris L.), sea buckthorn (Hippophae rhamnoides L.),
                                  spearmint (Mentha spicata L.), pennyroyal (Mentha pulegium L.)
Combination methods -          cumin (Cuminum cyminum), tobacco (Nicotiana tabacum)                        Li and others (2009), Zhang and others (2012)
  Solvent + Steam

(75 min, compared to 4 h in HD). Ohmic-assisted HD (OAHD)                           (energy cost is fairly higher to perform HD than that required for
is another advanced HD technique (Gavahian and others 2012).                        rapid MHG isolation), cleaner features (no residue generation and
OAHD method had the extraction time of 24.75 min, while HD                          no water or solvent used), increased antimicrobial and antioxidant
took 1 h for extraction of essential oil from thyme. No changes                     activities. Farhat and others (2011) studied the microwave steam
in the compounds of the essential oils obtained by OAHD were                        diffusion (MSDf), which is an advanced steam diffusion (SDf)
found in comparison with HD.                                                        technique utilizing microwave heating process for extraction of
   Hydrodiffusion. Hydrodiffusion extraction is a type of steam                     essential oils from by-products of orange peel. The essential oils
distillation, which is only different in the inlet way of steam into                extracted by MSDf for 12 min had similar yield and aromatic
the container of still. This method is used when the plant material                 profile to those obtained by SDf for 40 min.
has been dried and is not damaged at boiling temperature (Vian
and others 2008). For hydrodiffusion, steam is applied from the
top of plant material, whereas steam is entered from the bottom                     Solvent extraction
for steam distillation method. The process can also be operated                         Solvent. Conventional solvent extraction has been imple-
under low pressure or vacuum and reduces the steam temperature                      mented for fragile or delicate flower materials, which are not
to below 100 °C. Hydrodiffusion method is superior to steam                         tolerant to the heat of steam distillation. Different solvents in-
distillation because of a shorter processing time and a higher oil                  cluding acetone, hexane, petroleum ether, methanol, or ethanol
yield with less steam used. Bousbia and others (2009) compared the                  can be used for extraction (Areias and others 2000; Pizzale and
HD and innovative microwave hydrodiffusion and gravity (MHG)                        others 2002; Kosar and others 2005). For general practice, the
methods for their effectiveness in the isolation of essential oil from              solvent is mixed with the plant material and then heated to ex-
rosemary leaves (R. officinalis). The MHG method exhibits the                       tract the essential oil, followed by filtration. Subsequently, the
excellent advantages over traditional alternatives including shorter                filtrate is concentrated by solvent evaporation. The concentrate is
isolation times (15 min against 3 h for HD), environmental impact                   resin (resinoid), or concrete (a combination of wax, fragrance, and

                                                                                                       Vol. 79, Nr. 7, 2014 r Journal of Food Science R1235
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                     essential oil). From the concentrate, it is then mixed with pure      dant activity of separated essential oils from Thymus praecox subsp.
                     alcohol to extract the oil and distilled at low temperatures. The     skorpilii var. skorpilii (TPS) extracted using different solvents. TPS
                     alcohol absorbs the fragrance and when the alcohol is evaporated,     essential oil was found to contain thymol (40.31%) and o-cymene
                     the aromatic absolute oil is remained. However, this method is a      (13.66%) as the major components. The ethanol, methanol, and
                     relatively time-consuming process, thus making the oils more ex-      water extracts exerted significant free-radical scavenging activity.
                     pensive than other methods (Li and others 2009). Essential oil with   The water extract has the highest total phenolics (6.211 mg gal-
                     antioxidant activity from Ptychotisverticillata was extracted using   lic acid/g dry weight) and flavonoids (0.809 mg quercetin/g dry
                     solvent extraction method by El Ouariachi and others (2011).          weight). Moreover, Sarikurkcu and others (2009) reported that
                     The oil was dominated by phenolic compounds (48.0%) with car-         the water extract exhibited higher antioxidant activity than other
                     vacrol (44.6%) and thymol (3.4%) as the main compounds. Ozen          extracts (hexane, dichloromethane, ethyl acetate, and methanol).
                     and others (2011) studied the chemical composition and antioxi-       However, solvent residue could be retained in the final product

                     Figure 1–Diagrammatic illustration of steam distillation method.

                                                                                                                       Figure 2–Diagrammatic illustration of
                                                                                                                       hydrodistillation method.

                     R1236 Journal of Food Science r Vol. 79, Nr. 7, 2014
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Bioactivities and applications of essential oils . . .

                                                                                                                                                 in Food Science
due to incomplete removal. This may cause allergies, toxicity, and      It is a rapid extraction of essential oils from aromatic herbs,
affect the immune system (Ferhat and others 2007a).                     spices, and dry seeds. SFME has several advantages, involv-
    Supercritical carbon dioxide. Conventional methods in-              ing higher yield and selectivity, shorter time, and environmen-
cluding solvent extraction and steam distillation have some short-      tal friendly (Lopez-Avila and others 1994; Tomaniová and oth-
comings such as long preparation time and large amount of or-           ers 1998). SFME is a combination of microwave heating and
ganic solvents (Deng and others 2005). Moreover, the losses of          dry distillation, performed at atmospheric pressure without any
some volatile compounds, low extraction efficiency, degradation         solvent or water. Isolation and concentration of volatile com-
of unsaturated compounds, and toxic solvent residue in the extract      pounds are performed by a single stage (Lucchesi and others 2004;
may be encountered (Jimenez-Carmona and others 1999; Glišića          Bayramoglu and others 2008). Using oregano as a raw material,
and others 2007; Gironi and Maschietti 2008). Therefore, super-         SFME offered significantly higher essential oil yields (0.054 mL/g),
critical fluids have been considered as an alternative medium for       compared to HD (0.048 mL/g) (Bayramoglu and others 2008).
essential oil extraction. Carbon dioxide (CO2 ) is the most com-        When microwave power at 662 W was used in SFME, process time
monly used supercritical fluid because of its modest critical condi-    was reduced by 80%, compared with conventional process. Ferhat
tions (Hawthorne and others 1993; Jimenez-Carmona and others            and others (2007b) reported that microwave method offers the im-
1999; Senorans and others 2000). Under high-pressure condition,         portant advantages over traditional alternatives, such as shorter ex-
CO2 turns into liquid, which can be used as a very inert and            traction times (30 min compared with 3 h for HD and 1 h for cold
safe medium to extract the aromatic molecules from raw material.        pressing [CP]); better yields (0.24% compared with 0.21% for HD
No solvent residue remains in the final finished product since the      and 0.05% for CP); environmental impact (energy cost is appre-
liquid CO2 simply reverts to a gas and evaporates under normal          ciably higher for performing HD and for mechanical motors (CP)
atmospheric pressure and temperature. Despite high solubilities of      than that required for rapid microwave extraction); cleaner features
essential oil components in supercritical CO2 , the extraction rates    (as no residue generation and no water or solvent used); and high
were relatively slow with pure CO2 (ca. 80% recovery after 90           antimicrobial activities. Farhat and others (2010) reported that es-
min) (Hawthorne and others 1993). However, the combination              sential oils of caraway seeds isolated by microwave dry-diffusion
methods by a 15-min static extraction with methylene chloride           and gravity (MDG) exhibited the similar yield and aromatic profile
as a modifier followed by a 15-min dynamic extraction with pure         to those obtained by HD, but MDG was better than HD in terms
CO2 yielded high recoveries. The extraction efficacy was equiva-        of shorter process time (45 min compared with 300 min), energy
lent to HD, which was performed for 4 h. The volatile compounds         saving, and cleanliness. The present apparatus permits fast and
such as monoterpenes can be collected from the supercritical fluid      efficient extraction, reduces waste, avoids water and solvent con-
extraction (SFE) effluent by >90%. SFE was able to recover some         sumption, and allows substantial energy savings (Farhat and others
organic compounds that were not extracted by HD (Hawthorne              2010).
and others 1993). Pereira and Meireles (2007) showed that the
supercritical fluid extraction is economically viable than steam dis-   Role of Essential Oils as Food Additives
tillation. This is mainly caused by the lower yield and the higher        Essential oils from plants have been known to act as natural
energy consumption of the latter.                                       additives, for example, antimicrobial agents, antioxidant, and so on.
    Subcritical water. The subcritical water or pressurized hot         Their activities vary with source of plants, chemical composition,
water has been introduced as an extractant under dynamic condi-         extraction methods, and so on. Due to the unique smell associated
tions (pressure high enough to maintain water under liquid state        with the volatiles, this may limit the use of essential oil in some
and temperature in the range of 100 to 374 °C). Jimenez-Carmona         foods since it may alter the typical smell/flavor of foods.
and others (1999) reported that the efficiency (in terms of volume
of essential oil/1 g of plant) of continuous subcritical water ex-      Antimicrobial activity
traction was 5.1 times higher than HD method. This method is               The ability of plant essential oils to protect foods against
quicker (15 min compared with 3 h), provides a more valuable            pathogenic and spoilage microorganisms has been reported
essential oil (with higher amounts of oxygenated compounds and          (Lis-Balchin and others 1998; Friedman 2006; Rojas-Graü and
no significant presence of terpenes), and allows substantial savings    others 2007). Among chemical components in several essential
of costs, in terms of both energy and plant material. Kubatova          oils, carvacrol has been shown to exert a distinct antimicrobial
and others (2001) studied the subcritical water extraction of lac-      action (Veldhuizen and others 2006). Carvacrol is the major com-
tones from a kava (Piper methysticum) root, compared to a Soxhlet       ponent of essential oil from oregano (60% to 74% carvacrol) and
extraction with water. The extraction of ground samples with sub-       thyme (45% carvacrol) (Lagouri and others 1993; Arrebola and
critical water at 100 °C took 2 h, but the shorter time (20 min)        others 1994). It has a broad spectrum of antimicrobial activity
was required when extraction was carried out at 175 °C. Boiling         against most gram-positive and gram-negative bacteria (Friedman
for 2 h and extraction with Soxhlet apparatus for 6 h showed the        and others 2002). Carvacrol disintegrates the outer membrane of
lower yields by 40% to 60%, compared with that obtained using           gram-negative bacteria, releasing lipopolysaccharides and increas-
subcritical water.                                                      ing the permeability of the cytoplasmic membrane to ATP (Burt
                                                                        2004). For gram-positive bacteria, it is able to interact with the
Solvent-free microwave                                                  membranes of bacteria and alter the permeability for cations like
  The disadvantages of conventional methods such as solvent or          H+ and K+ (Veldhuizen and others 2006). In general, the higher
hydrodiffusion extraction are the losses of some volatile com-          antimicrobial activity of essential oils is observed on gram-positive
pounds, low extraction efficiency, long extraction time, degra-         bacteria than gram-negative bacteria (Kokoska and others 2002;
dation of unsaturated or ester compounds through thermal or             Okoh and others 2010). Lipophilic ends of lipoteichoic acids in
hydrolytic effects, and toxic solvent residue in the extract (Pollien   cell membrane of gram positive bacteria may facilitate the pen-
and others 1998; Luque de Castro and others 1999). These dis-           etration of hydrophobic compounds of essential oils (Cox and
advantages have led to the consideration of the use of SFME.            others 2000). On the other hand, the resistance of gram-negative

                                                                                      Vol. 79, Nr. 7, 2014 r Journal of Food Science R1237
R: Concise Reviews   Bioactivities and applications of essential oils . . .
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                     bacteria to essential oils is associated with the protecting role of ex-        2010), which possess strong antimicrobial activity by the disrup-
                     trinsic membrane proteins or cell wall lipopolysaccharides, which               tion of bacteria membrane integrity (Knobloch and others 1989).
                     limits the diffusion rate of hydrophobic compounds through the                  Aguirre and others (2013); Burt (2004); and Pelissari and oth-
                     lipopolysaccharide layer (Burt 2004). The dissipation of ion gra-               ers (2009) also reported that oregano essential oil had higher
                     dients leads to impairment of essential processes in the cell and               antimicrobial activity against the gram-positive bacteria (S. au-
                     finally to cell death (Ultee and others 1999). The cytoplasmic                  reus) than gram-negative (E. coli and Pseudomonas aeruginosa). The
                     membrane of bacteria generally has 2 principal functions: (i) bar-              main constituents of oregano essential oil are thymol, carvacrol,
                     rier function and energy transduction, which allow the membrane                 γ -therpinene, and ρ-cymene (Lambert and others 2001; Burt
                     to form ion gradients that can be used to drive various processes,              2004; Aguirre and others 2013). However, Pseudomonas putida was
                     and (ii) formation of a matrix for membrane-embedded proteins                   resistant to carrot seed and parsley essential oils (Teixeira and oth-
                     (such as the membrane-integrated F0 complex of ATP synthase)                    ers 2013). E. coli and Salmonella typhimurium were also tolerant to
                     (Sikkema and others 1995; Hensel and others 1996). Antimicro-                   carrot seed, grapefruit, lemon, onion, and parsley essential oils.
                     bial mechanism of essential oil is proposed as shown in Figure 3.               The greater resistance of gram-negative bacteria toward essential
                     The activity of the essential oils is related to composition, func-             oils may be attributed to the complexity of their double-layer cell
                     tional groups, and synergistic interactions between components                  membrane, compared with the single-layer membrane of gram-
                     (Dorman and Deans 2000). The removal of the aliphatic ring sub-                 positive bacteria (Hogg 2005).
                     stituent of carvacrol slightly decreased the antimicrobial activity.               Antimicrobial activity of Callistemon comboynensis essential oil
                     2-Amino-ρ-cymene has similar structure to cavacrol, except hy-                  was observed against gram-positive (B. subtilis and S. aureus), gram-
                     droxyl group (Figure 4). The lower activity by 3-fold of 2-amino-               negative (Proteus vulgaris and P. aeruginosa), and a pathogenic fungus
                     ρ-cymene, as compared to carvacrol, indicates the essential role of             Candida albicans. This might be associated with the high content
                     hydroxyl group in antimicrobial activity of carvacrol (Veldhuizen               of oxygenated constituents (Abdelhady and Aly 2012). Essential
                     and others 2006). The hydroxyl group present in the structure of                oil of C. comboynensis leave consisted of 1,8-cineole (53.03%),
                     phenolic compounds confers antimicrobial activity and its relative              eugenol (12.1%), methyl eugenol (8.3%), α-terpineol (4.3%), and
                     position is very crucial for the effectiveness of these natural com-            carveol (3.4%) (Abdelhady and Aly 2012). Teixeira and others
                     ponents; this can explain the superior antimicrobial activity of car-           (2013) found that the highest reduction (8.0 log CFU/mL) was
                     vacrol, compared to other plant phenolics (Veldhuizen and others                obtained when coriander, origanum, and rosemary essential oils
                     2006).                                                                          at a level of 20 μL were used to inhibit Listeria innocua. Thyme
                        Plant essential oils have been known as antimicrobial agents. Es-            essential oil (20 μL) was able to inhibit both L. innocua and Lis-
                     sential oil of rosemary (R. officinalis) exhibited both gram-positive           teria monocytogenes. However, rosemary essential oil exhibited the
                     (Staphylococcus aureus and Bacillus subtilis) and gram-negative (Es-            highest MIC (90.8 mg/mL) against Brochothrix thermosphacta and
                     cherichia coli and Klebsiella pneumoniae) bacteria (Okoh and others             S. typhimurium. Thus, essential oils from the selected plants can be
                     2010). The major components of rosemary oil are monoterpenes                    used as antimicrobial agents for food applications as well as other
                     such as α-pinene, β-pinene, myrcene 1,8-cineole, borneol, cam-                  purposes; however, their activity depends on types of essential oil
                     phor, and verbinone (Santoyo and others 2005; Okoh and others                   used.

                     Figure 3–Schematic illustration for the effect of essential oils on bacteria cell.

                     R1238 Journal of Food Science r Vol. 79, Nr. 7, 2014
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Bioactivities and applications of essential oils . . .

                                                                                                                                                      in Food Science
Antioxidant activity                                                     others 2007), m-thymol in thyme (Bozin and others 2006), and
   Several compounds in essential oils have the structure mim-           β-citronellol or β-citronellal in citronella (Ruberto and Baratta
icking the well-known plant phenols with antioxidant activity.           2000). However, the other antioxidant compounds in essential
Among the major compounds available in the oil, thymol and               oils such as terpinene, (−)-camphor, (−)-bornylacetate, eucalyp-
carvacrol were reported to possess the highest antioxidant activity      tol, and methylchavicol have been reported to exhibit antioxidant
(Dapkevicius and others 1998). Essential oils have several modes         activity, but their amounts were probably too low to exhibit an-
of actions as antioxidant, such as prevention of chain initiation,       tioxidant activity (Ruberto and Baratta 2000; Mitić-Ćulafić and
free radical scavengers, reducing agents, termination of peroxides,      others 2009; Teixeira and others 2013). Antioxidant activity varies
prevention of continued hydrogen abstraction as well as quenchers        with source of essential oils. Tongnuanchan and others (2013a)
of singlet oxygen formation and binding of transition metal ion          reported that among essential oils from roots, plai essential oil
catalysts (Yildirim and others 2000; Mao and others 2006). With          showed the highest DPPH radical scavenging activity, followed
those functions, essential oils can serve as the potential natural an-   by turmeric and ginger essential oil, respectively. The highest
tioxidants, which can be used to prevent lipid oxidation in food         2,2-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS)
systems. Phenolics are organic compounds consisting of hydroxyl          radical scavenging activity was observed in turmeric essential oil,
group (-OH) attached directly to a carbon atom that is a part            followed by plai and ginger essential oils. The differences in an-
of aromatic ring. The hydrogen atom of hydroxyl group can be             tioxidative activity of different essential oils were mostly due to
donated to free radicals, thereby preventing other compounds to          the differences in types and amounts of antioxidative components
be oxidized (Nguyen and others 2003). Teixeira and others (2013)         present in essential oils (Burt 2004; Kordali and others 2005).
reported that the highest scavenging activity of DPPH radical was           Antioxidative activity of essential oil is also affected by extraction
observed for clove and origanum essential oils with the EC50 val-        method or solvents used. Sarikurkcu and others (2010) reported
ues of 35.7 ± 1.2 and 46.8 ± 0.4 μg/mL, respectively. Clove and          that free radical scavenging activity (DPPH assay) and reducing
origanum essential oils also showed the high ferric reducing power       power of essential oil from Thymus longicaulis subsp. Longicaulis
(Teixeira and others 2013). The antioxidant capability of phenolic       var. longicaulis extracted using HD method was lower than those
compounds is mainly due to their redox properties, which permit          extracted using methanol or water. Methanol extract of Salvia
them to act as hydrogen donors, reducing agents, singlet oxygen          tomentosa exhibited superior radical scavenging activity to other
quenchers as well as metal chelators (Kumar and others 2005).            extracts (IC50 = 18.7l μg/mL) (Tepe and others 2005). Nonpolar
The antioxidant activity is generally related with the major ac-         extracts showed less effective activities than polar extracts. There-
tive compounds in essential oils such as eugenol in clove (Wei           fore, antioxidative activity of essential oil is strictly related with
and Shibamoto 2010), carvacrol in origanum (Bounatirou and               the polarities of their phytochemicals. The antioxidant activity of

                                                                                                  Figure 4–Structure of carvacrol and
                                                                                                  carvacrol-related compounds
                                                                                                  Source: Veldhuizen and others (2006).

                                                                                        Vol. 79, Nr. 7, 2014 r Journal of Food Science R1239
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                     essential oil from T. longicaulis subsp. longicaulis var. longicaulis ex-   essential oils (Turina and others 2006). Hydrophobic essential oil
                     tracted by HD method at 2.0 mg/mL showed similar antioxidative              could increase the hydrophobicity of films, thereby reducing the
                     activity to synthetic antioxidants butylated hydroxytoluene (BHT)           water vapor migration through the film. Essential oils with low
                     and butylated hydroxyanisole (BHA) when tested by β-carotene–               density are separated and localized at the upper surface of film,
                     linoleic acid model system and was higher than those extracted              thereby forming the bilayer microstructure. In general, there was
                     with other solvents (Sarikurkcu and others 2010). In contrast, the          no oil exudates on the film incorporated with low concentration
                     inhibition of linoleic acid oxidation of model system by essential          (25%) of essential oil; however, at high concentration of essen-
                     oil of S. tomentosa (Miller) was lower than those extracted using           tial oil (100%), some oil exudates were found at the surface of
                     solvents with different polarities and BHT (Tepe and others 2005).          the films. The bilayer-morphological microstructure might con-
                     Abdelhady and Aly (2012) reported that C. comboynensis essential            tribute to lower WVP of essential-oil-incorporated gelatin films
                     oil exhibited the antioxidant activity at a concentration of 1000           (Figure 5), compared with the control film. Atarés and others
                     μg/mL (91.1 ± 0.3% inhibition), comparable to 100 μg/mL gallic              (2010a) studied the mechanical properties of soy protein isolate
                     acid (95.7 ± 2% inhibition). It has been reported that nonphe-              incorporated with cinnamon and ginger essential oil at differ-
                     nolic antioxidants of plant extracts might also contribute to the           ent concentrations (protein to oil mass ratios: 1 : 0.025, 1 : 0.050,
                     antioxidant activity (Newman and others 2002; Hassimotto and                1 : 0.075, and 1 : 0.100). A slight decreasing trend of elastic mod-
                     others 2005).                                                               ulus (EM) was observed as the oil content increased. The WVP
                        Additionally, the harvesting period of plant also determines the         was slightly reduced by both essential oils. The oil type signifi-
                     concentration of the major oil components such as phenolic com-             cantly affected both tensile strength (resistance to elongation) and
                     pounds, which directly related with the antioxidant activity of             EM (capacity for stretching) (Atarés and others 2010a). Essen-
                     essential oils (Malatova and others 2011; Zheljazkov and others             tial oils may cause some degree of rearrangement in the protein
                     2012; Wu and others 2013).                                                  network, thus strengthening and increasing the film resistance to
                                                                                                 elongation. Moreover, Pires and others (2011) studied the effect
                     Active Packaging Containing Essential Oils                                  of thyme essential oil incorporated in hake protein film. The ad-
                     and Applications                                                            dition of thyme oil significantly reduced the WVP. Nevertheless,
                                                                                                 the addition of essential oil had impact on the transparency of film,
                     Development of active packaging                                             depending on type and concentration of essential oils. The addi-
                        Nowadays, smart packaging has gained increasing attention, for           tion of thyme oil decreased the transparency value of hake proteins
                     example, antimicrobial packaging, which can be applied to ex-               films (Pires and others 2011). Table 4 presents the properties of
                     tend the shelf life of food and products (Appendini and Hotchkiss           protein-based films containing various essential oils.
                     2002; Quintavalla and Vicini 2002). To enhance the property of                 The ability of plant essential oils to protect foods against
                     those packaging, antimicrobial compounds or extracts with the se-           pathogenic and spoilage microorganisms has been reported by
                     lected bioactivity are incorporated. Thus, several approaches have          several researchers (Lis-Balchin and others 1998; Friedman 2006;
                     been introduced, not only for increasing bioactivity but also mod-          Rojas-Graü and others 2007). Film or packaging incorporated
                     ifying the property of biomaterials used for packaging. Among               with essential oils can be employed as active packaging due to their
                     biomaterials, proteins have gained attention, due to their vari-            antimicrobial or antioxidant activities. Seydim and Sarikus (2006)
                     ety in compositions, properties, as well as nutritive value. How-           evaluated antimicrobial activity of whey-protein isolate-based edi-
                     ever, protein-based material for packaging is still encountering the        ble films incorporated with oregano essential oil. Oregano essential
                     poor property, especially poor barrier property toward water va-            oil added films exhibited the larger inhibitory zone on S. aureus
                     por. Chemical and enzyme treatment can be applied to modify                 with increasing levels of essential oil added. Table 5 presents the an-
                     polymer network through the cross-linking of the polymer chains             timicrobial activities of biopolymer films containing various types
                     to improve the properties of protein film (Mahmoud and Savello              of essential oils.
                     1993; Yildirim and Hettiarachchy 1997; De Carvalho and Grosso                  Films added with essential oils are shown to possess antioxi-
                     2004). Hydrophobic plasticizer can be used to improve water va-             dant activities, which can vary with type and amount of essen-
                     por barrier property of films. However, it may yield films with             tial oil incorporated. Gómez-Estaca and others (2009) reported
                     different properties. The incorporation of hydrophobic substances           that bovine-hide and tuna skin gelatin films supplemented with
                     such as lipid, fatty acid, wax, and so on, has been implemented to          oregano and rosemary extracts exhibited the reducing ability and
                     improve water vapor barrier property (Prodpran and others 2007;             free-radical scavenging capacity. Antioxidant power was gener-
                     Limpisophon and others 2010; Soazo and others 2011). Hy-                    ally being proportional to the amount of added extract. Gelatin
                     drophobic materials such as essential oils have been incorporated           films incorporated with different essential oils containing 30%
                     to improve water vapor barrier property of protein-based films,             glycerol mostly had the higher antioxidant activity than those
                     for example, film from fish muscle protein, film from fish gelatin,         with 20% glycerol (P < 0.05) (Tongnuanchan and others 2012).
                     and so on (Atarés and others 2010a; Tongnuanchan and others                More loosen structure of film network found in film contain-
                     2012, 2013a). Tongnuanchan and others (2012) reported that wa-              ing 30% glycerol favored the release of essential oils with antiox-
                     ter vapor permeability (WVP) of fish skin gelatin film decreased            idative activity (Tongnuanchan and others 2012). Antioxidative
                     markedly from 3.11 to 1.88, 1.89, and 2.45 × 10−11 gm−1 s−1 Pa−1            activities of gelatin films incorporated with essential oils were
                     (P < 0.05), when films were incorporated with ginger, turmeric,             lower than those of pure essential oil, regardless of type of essen-
                     and plai essential oils, respectively, at a level of 100% based on pro-     tial oil used. The interaction between gelatin and antioxidative
                     tein. The incorporation of ginger, turmeric, and plai essential oils        compounds in essential oil thus lowers the release of those com-
                     at the highest level (100% based on protein) reduced WVP of film            pounds (Tongnuanchan and others 2013a). Antioxidant activities
                     by 39.54%, 39.22%, and 21.22%, respectively. The result suggested           of protein-based films containing various essential oils are shown in
                     different hydrophobicity of compounds present in different essen-           Table 6.
                     tial oils used. Monoterpenes are highly hydrophobic substances                 However, film or packaging may have the smell of essential
                     found in essential oils, in which the content varied with types of          oils due to its volatilization. The smell intensity of essential oil in

                     R1240 Journal of Food Science r Vol. 79, Nr. 7, 2014
Table 4–Properties of biopolymer films containing various types of essential oils.

                                                                                                                                                                                     Mechanical properties
                                                       Protein type,             Plasticizer,                      Essential oils,                                                                                           WVP(×10−1 0             Transparency
                                                       concentration            concentration                      concentration                      Thickness(mm)              TS (MPa)                EAB (%)              g/m s Pa)                  (%)                  References
                                                       Hake muscle            Glycerol, 59%          Thyme (Thymus vulgaris L.), 0.025, 0.05,          0.022 to 0.025        4.13 to 6.67,3.30        111.2 to 129.8,          0.35 to 0.43             1.8 to 6.5        Pires and others
                                                       protein,1.5%           (w/w) of protein       0.1, and 0.25 mL oil/g protein                                             to 8.49 N             87.87 to 115.41                                                     (2011)
                                                       (w/w) of FFS                                                                                                          (Breaking force)            (Puncture
                                                       Soy protein isolate,   Glycerol, 30%          Cinnamon(Cinnamomum verum), 0.025,                        –                11.0 to 17.6             3.4 to 7.5           0.46 to 0.64a                 –             Atarés and others
                                                       8% (w/w) of FFS        (w/w) of protein       0.05, 0.075, and 0.1 mL oil/g protein                                                                                                                                (2010a)
                                                                                                     Ginger(Zingiber officinale), 0.025, 0.05,                 –                    4 to 8                1.7 to 3            0.56 to   0.68a               –
                                                                                                     0.075, and 0.1 mL oil/g protein
                                                       Sodium caseinate,      Glycerol, 30%          Cinnamon (Cinnamomum verum), 0.025                        –                 22 and 24b             13 and 22b           0.64 and 0.57d                 –             Atarés and others
                                                                                                                                                                                                                                                                                                Bioactivities and applications of essential oils . . .

                                                       8% (w/w) of FFS        (w/w) of protein       and 0.075 mL oil/g protein                                                10.2 and 11.4c           67 and 76c            2.14 and 1.7e                               (2010b)
                                                                                                     Ginger(Zingiber officinale), 0.025 and                    –                 22 and 22b             18 and 16b           0.57 and 0.52d                 –
                                                                                                     0.075 mL oil/g protein                                                     10 and 11.6c            57 and 72c             2.1 and 1.8e
                                                       Sunflower protein      Glycerol, 1.5%         Clove(Syzygium aromaticum)                         0.080 ± 0.01              2.5 ± 0.2             24.9 ± 1.7           1.16 ± 0.09aa                  –             Salgado and others
                                                       concentrate, 5%        (w/v) of FFS                                                                                                                                                                                (2013)
                                                       (w/v) of FFS
                                                       Fish gelatin           Glycerol,20% and       Bergamot (Citrus bergamia), 50% (w/w)             0.047 and 0.048        42.42 and 36.52        15.29 and 19.19         3.15 and 3.22aaa        4.28 and 4.45        Tongnuanchan
                                                       (tilapia), 3.5%        30% (w/w) of           of protein                                                                                                                                                           and others (2012)
                                                       (w/w) of FFS           protein
                                                                                                     Kaffir Lime Peel (Citrus hystrix DC)              0.048 and 0.047        36.87 and 34.22        31.43 and 30.93          2.95 and 3.38          5.48 and 5.56
                                                                                                     Lemon, (Citrus limon)                             0.048 and 0.048        32.82 and 31.06        39.06 and 52.66          2.81 and 2.85          5.46 and 5.31
                                                                                                     Lime, (Citrus aurantifolia)                       0.049 and 0.047        27.32 and 25.87        52.21 and 69.79          2.91 and 3.37          5.66 and 5.46
                                                       Fish gelatin           Glycerol, 30%          Ginger(Zingiber officinale), 25%, 50%, and         0.041 to 0.057         18.58 to 35.73         41.70 to 72.03          1.88 to 2.61aaa         1.60 to 3.02        Tongnuanchan
                                                       (tilapia), 3.5%        (w/w) of protein       100% (w/w) of protein                                                                                                                                                and others (2013a)
                                                       (w/w) of FFS
                                                                                                     Tumeric(Curcuma longa)                            0.041 to 0.053          23.34 to 34.04         42.96 to 72.80          1.89 to 2.48            1.45 to 1.63
                                                                                                     Plai(Zingiber cassumunar roxb)                    0.041 to 0.055          17.20 to 32.06         44.96 to 74.68          2.45 to 2.91            1.49 – 2.17
                                                       Fish gelatin           Glycerol, 30%          Lemongrass, (Cymbopogon citratus)                 0.056 to 0.073          18.42 to 25.13         52.81 to 77.25          1.41 to 1.79†           2.48 to 3.24        Tongnuanchan
                                                       (tilapia), 3.5%        (w/w) of protein                                                                                                                                                                            and others (2013b)
                                                       (w/w) of FFS
                                                                                                     Basil, (Ocimum sanctum)                           0.054 to 0.084          18.70 to 21.37         46.53 to 85.06           1.20 to 2.11           2.18 to 3.26
                                                                                                     Citronella, (Cymbopogon nardus)                   0.068 to 0.080          17.39 to 21.85         44.63 to 97.29           1.07 to 1.42           3.67 to 4.41
                                                                                                     Kaffir Lime Leaf, (Citrus hystrix DC)             0.066 to 0.081          25.07 to 26.21         43.95 to 95.08           1.03 to 1.59           4.25 to 6.08
                                                        FFS = Film forming solution; WVP = water vapor permeability; a WVP unit (g mm/m2 h kPa); aa WVP unit (1010 g H2 O/Pa m s); † WVP unit (1010 g H2 O/Pa m s); b, c Final moisture content in the film: 5 and 10 g water/100 g film,
                                                       respectively; d, e WVP of films tested at 25 °C and 2 range of relative humidity (RH) (33% to 53% and 53 to 75, respectively).

Vol. 79, Nr. 7, 2014 r Journal of Food Science R1241
                                                                                                                                                                                                                                                                                  R: Concise Reviews
                                                                                                                                                                                                                                                                                   in Food Science
in Food Science
                                                                                                                                                                                                                                                            R: Concise Reviews

                                                       Table 5–Antimicrobial effect of biopolymer films containing various types of essential oils.

                                                       Film forming                     Plasticizer,                   Essential oils,
                                                       materials, concentration        concentration                   concentration                              Tested organisms                                  Inhibition effect                References
                                                       Soy protein isolate, 5%    Glycerol,                     Oregano (Oreganum             Staphylococcus aureus                                           27.50 to   49.50a               Emiroğlu and others
                                                                                                                  heracleoticum L.),                                                                                                            (2010)
                                                       (w/v) of FFS               3.5% (w/v) of FFS             1%, 2%, 3%, 4%, and 5%        Escherichia coli                                                32.00 to 45.50
                                                                                                                  (v/v) of FFS
                                                                                                                                              Escherichia coli O157:H7                                        35.50 to 50.50
                                                                                                                                              Pseudomanas aeruginosa                                          27.00 to 39.50
                                                                                                                                              Lactobacillus plantarum                                         22.50 to 37.00
                                                                                                                Thyme (Thymusvulgaris L.)     Staphylococcus aureus                                           30.00 to 49.50

R1242 Journal of Food Science r Vol. 79, Nr. 7, 2014
                                                                                                                                                                                                                                                                           Bioactivities and applications of essential oils . . .

                                                                                                                                              Escherichia coli                                                36.50 to 49.00
                                                                                                                                              Escherichia coli O157:H7                                        36.50 to 49.50
                                                                                                                                              Pseudomanas aeruginosa                                          32.50 to 42.00
                                                                                                                                              Lactobacillus plantarum                                         20.50 to 36.50
                                                       Bovine-hide gelatin,       Sorbitol and glycerol, 0.15   Clove (Syzygium aromaticum    Pseudomonas fluorescens                                         9.07 ± 0.13b                    Gómez-Estaca and others
                                                                                    and 0.15 g/g gelatin           L.)                                                                                                                          (2010)
                                                       8% (w/v) of FFS                                          0.75 ml/g biopolymer          Lactobacillus acidophilus                                       12.76 ± 2.51
                                                                                                                                              Listeria innocua                                                7.46 ± 0.53
                                                                                                                                              Escherichia coli                                                10.64 ± 1.37
                                                       Gelatin-Chitosan,          Sorbitol and glycerol, 0.15   Clove (Syzygium aromaticum    Pseudomonas fluorescens                                         9.51 ± 2.03b
                                                                                    and 0.15 g/g gelatin           L.)
                                                       6% of gelatin plus 2% of                                 0.75 mL/g biopolymers         Lactobacillus acidophilus                                       12.60 ± 3.42                    Gómez-Estaca and others
                                                         chitosan (w/v) of FFS                                                                                                                                                                  (2010)
                                                                                                                                              Listeria innocua                                                6.42 ± 0.41
                                                                                                                                              Escherichia coli                                                8.69 ± 0.42
                                                       Whey protein isolate,      Glycerol, 5% (w/v) of FFS     Oregano (Origanum             Escherichia coli O157:H7 Staphylococcus aureus Salmonella       0 to 37.09c 0 to 43.07 0 to     Seydim and Sarikus (2006)
                                                        5% (w/v) of FFS                                           minutiflorum) 1%, 2%, 3%,      enteritidis Listeria monocytogenes Lactobacillus plantarum      40.59 0 to 41.650 to 13.45
                                                                                                                  and 4% (v/v) of FFS
                                                                                                                Rosemary (Rosmarinus          Escherichia coli O157:H7 Staphylococcus aureus Salmonella       0 to 11.36 0 to 13.45 0 to
                                                                                                                  officianalis L.)              enteritidis Listeria monocytogenes Lactobacillus plantarum       10.48 0 to 11.96 0 to 9.21
                                                                                                                Garlic (Allium sativum L.),   Escherichia coli O157:H7 Staphylococcus aureus Salmonella       N.D. N.D. N.D. N.D. N.D.
                                                                                                                                                enteritidis Listeria monocytogenes Lactobacillus plantarum
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