A Comparison of the Nutritional Value, Sensory Qualities, and Food Safety of Organically and Conventionally Produced Foods
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
Critical Reviews in Food Science and Nutrition, 42(1):1–34 (2002)
A Comparison of the Nutritional Value, Sensory
Qualities, and Food Safety of Organically and
Conventionally Produced Foods
Diane Bourn and John Prescott
Department of Food Science, University of Otago, PO Box 56, Dunedin, New Zealand
Referee: Dr. William Lockeretz, Professor, School of Nutrition Science and Policy, Tufts University, Medford, MA 12155
* Address for Correspondence: Diane Bourn, Department of Food Science, University of Otago, PO Box 56, Dunedin, New Zealand.
Email: diane.bourn@stonebow.otago.ac.nz. Phone +64 3 479 7552. Fax +64 3 479 7567
Key Words: Organic food, sensory, nutritional value, food safety.
ABSTRACT: Given the significant increase in consumer interest in organic food products, there is a need to
determine to what extent there is a scientific basis for claims made for organic produce. Studies comparing foods
derived from organic and conventional growing systems were assessed for three key areas: nutritional value,
sensory quality, and food safety. It is evident from this assessment that there are few well-controlled studies that
are capable of making a valid comparison. With the possible exception of nitrate content, there is no strong
evidence that organic and conventional foods differ in concentrations of various nutrients. Considerations of the
impact of organic growing systems on nutrient bioavailability and nonnutrient components have received little
attention and are important directions for future research. While there are reports indicating that organic and
conventional fruits and vegetables may differ on a variety of sensory qualities, the findings are inconsistent. In
future studies, the possibility that typical organic distribution or harvesting systems may deliver products differing
in freshness or maturity should be evaluated. There is no evidence that organic foods may be more susceptible to
microbiological contamination than conventional foods. While it is likely that organically grown foods are lower
in pesticide residues, there has been very little documentation of residue levels.
I. INTRODUCTION tion system, to consider the wider social and eco-
logical impact of the food production and pro-
A. What is “Organically Grown Food”? cessing system, and to produce food of high qual-
ity in sufficient quantity.1
The term “organically grown food” denotes Certified organic food and fiber products are
products that have been produced in accordance those that have been produced according to docu-
with the principles and practices of organic agri- mented standards. There are hundreds of organic
culture. Organic agricultural and food processing certifying agencies around the world that estab-
practices are wide ranging and overall seek to lish their own production standards and certifica-
foster the development of a food production sys- tion processes. A small number of these agencies
tem that is socially, ecologically, and economi- have gained accreditation from the International
cally sustainable. The key principles and prac- Federation of Organic Agricultural Movements
tices of organic food production aim to encourage (IFOAM), based on verification that the agencies
and enhance biological cycles within the farming are operating in accordance with the IFOAM Basic
system to maintain and increase long-term fertil- Standards. In addition, some certification agen-
ity of soils, to minimize all forms of pollution, to cies have gained ISO accreditation (e.g., ISO 65
avoid the use of synthetic fertilizers and pesti- for certifiers) and/or been audited by government
cides, to maintain genetic diversity of the produc- agencies giving the certifiers another level of in-
1040-8398/02/$.50
© 2002 by CRC Press LLC
1dependent verification of their standards and op- sumer demand for organic foods, although the
erating systems. relative importance of factors influencing the
For the purposes of this review, terms such as purchase of organic foods may vary from country
“ecological” farming and “biological” farming to country. Frequently, surveys report pesticide
have been considered to be synonymous with residues in food (i.e., concerns for own health) to
“organic” farming. However, a distinction needs be more important in the decision to purchase
to be made between organic and bio-dynamic organic food products than concerns for the envi-
farming systems. Bio-dynamic farming systems, ronment as a whole, although this factor is more
based on the teachings of Rudolf Steiner, incor- important in some countries.8-14
porate the principles and practices of organic ag- For example, consumers in Germany have
riculture but also include some unique practices. tended to be more concerned with environmental
For example, bio-dynamic farmers may apply issues than those in the UK,9,15 although this may
preparations of cow manure, herbs, minerals, etc. be changing with more recent reports suggesting
to composts and directly to the land and they that approximately 70% of organic consumers
commonly take into account the position of the cite health as the primary reason for purchasing
planets and the moon in deciding what tasks to organic food.16 In the USA, consumers who con-
carry out at a particular time of the month.2 sidered organic foods to be better than conven-
tional foods believed that the following character-
istics (in decreasing order of importance) were
B. The Organic Food Industry important when they purchased organic foods:
safety, freshness, general health benefits, nutritional
Over the last few years the organic food indus- value, effect on environment, flavor, and general prod-
try has been showing the highest levels of growth of uct.17 Goldman and Clancy18 reported that organic
all food sectors. In the USA, the market for organic food buyers at a cooperative in New York believed
foods increased 40-fold from 1986 to 1996, and at protection of wildlife and water supplies from pesti-
the end of 1999 estimated to be worth over $4.2 cide contamination was the most important reason for
billion annually, and is predicted to continue to grow supporting organic agriculture, followed by protec-
at a rate of more than 24% per year.3 In the UK, the tion of drinking water supplies from fertilizer con-
organic market is estimated to be worth over US$567 tamination and protection of consumers from pesti-
million4 and accounts for 3 to 4% of all food sales.5 cide residues in food. Frequent purchasers of organic
Organic markets in some other European countries products were less concerned with price and product
are considerably larger than that in the UK. For appearance. A group of Norwegian organic consum-
example, Germany has the largest of the European ers identified health and environmental reasons for
markets worth over US$1.92 billion in 1997.4 In purchasing organic foods.19 In this study, the young-
New Zealand, the value of the organic export market est age group (15 to 24 years) named consideration
was estimated to be over NZ$70 million in 2000/ for the environment and animal welfare as key rea-
2001,6 close to a 3-fold increase from 1997.7 The sons for purchasing organic food, whereas in the
New Zealand domestic organic market was esti- older age groups concern for their own health was the
mated to be worth NZ$50 million in 2000/2001.6 It most important reason.
is predicted that the value of the total New Zealand In a comprehensive study investigating health-
organic industry (export and domestic markets) may related determinants of organic food consump-
increase to NZ$500 million by 2005.6 tion in the Netherlands,20 the importance of health
and environmental factors in influencing the de-
cision to purchase organic foods was found to
C. Why Do Consumers Choose Organic vary with the frequency of purchase. Health was
Food? found to be a more important motive for “inciden-
tal” buyers, whereas environmental reasons were
A number of studies have identified the rea- found to be a more important factor for “heavy”
sons behind these considerable increases in con- buyers of organic foods. This finding suggests
2that when surveys of organic purchasers are car- Schifferstein and Oude Ophuis20 suggest that
ried out, the study participants should be classi- organic food buyers tend to be health conscious
fied according to frequency of purchase. and believe that the type of food they choose to
Consumers have also been found to have spe- eat affects their health. In addition, organic con-
cific reasons for not purchasing organically grown sumers are more willing to sacrifice some money,
foods, including: appearance, and ease of preparation when pur-
chasing organic products. Overall, purchasing
• Too expensive12,21-24 organic food is part of a way of life for such
• Poor availability and lack of time to find retail people and reflects a particular ideology and value
outlets (when organic products are not readily system.
available in supermarkets)19,21-23,25 The way in which consumers decide to pur-
• Unsatisfactory quality (possibly mainly focused chase organic products has also been investi-
on appearance of fresh produce)21,22,24 gated.13,25,29,30,31 A model developed for the pur-
• Satisfaction with their current food purchases; chase of organic foods includes four stages: cue
do not think organic food is any better22 utilization (organically grown label, naturally pro-
• Unfamiliarity with the term “organic”, certifi- cessed, price); integration of cues to an overall
cation systems and organic logos.19.21 quality perception (health and environmental con-
cerns); trade-off of perceived quality and cost
Some researchers have attempted to develop (higher prices may lead to higher perceived value
a profile of the consumer of organic foods. These but price is also sacrificed in the product pur-
consumers have been classified into four broad chase); influence of perceived value on willing-
(and presumably overlapping) groups: (1) those ness to buy (the willingness to pay more for or-
who are concerned with the environment, (2) food ganic products than for conventional products is
phobics who are concerned about chemical resi- in most cases fundamental for success of the
dues in food, (3) humanists concerned with fac- market).29 In this study, organic extra virgin olive
tory farming, and (4) hedonists who believe that oil was used to test the model and various market-
a premium product must be better and more im- ing actions were identified that might increase the
portantly taste better.26 In an Irish study, the typi- likelihood that the product would be purchased.
cal organic food purchaser was more likely to be For example, product labeling should indicate the
female with a higher level of disposable income.26 naturalness of the product and that it has been
Secondary factors influencing organic food pur- produced in accordance with recognized standards
chase were the presence of children and being in and that overall the product promotion should
the 30 to 49 year age group, although unlike other strongly link its attributes to product benefits such
studies age group was not found to be a particu- as environmental friendliness.
larly significant factor. In a Californian study,27 Hutchins and Greenhalgh13 suggest that be-
organic food buyers were found to be older than cause of confusion of consumers over the word
nonbuyers and were more likely to be in service “organic”, such products may be more success-
and white-collar occupations. Govindasamy and fully marketed in a broader way as “environmen-
Italia28 reported higher income earners and younger tally friendly”. These authors strongly recommend
people were more willing to purchase Integrated that a cohesive marketing strategy is needed in
Pest Management (IPM) produce than lower in- order to fulfill the increasingly complex needs of
come earners and older people. Another Ameri- consumers. Store type and convenience of store
can study reported that income and age were not location is another factor that can markedly influ-
important factors in distinguishing between or- ence the purchase of organic products, and this
ganic food buyers and nonbuyers.18 Wandel and could be an important factor in understanding
Bugge19 have also reported that interest in organic where potential growth in organic foods might
food in Norway was not related to income, occu- occur.23,25,31 A variety of distribution methods for
pation, age, or presence of children in the house- organic produce are used around the world, in-
hold. cluding direct supply from farmers to consumers,
3health food shops, specialist organic retailers, produced food is going to be an important factor
supermarkets, farmers markets, and food coop- in ensuring a sustainable food supply61-63 and that
eratives.32-35 The relative importance or dominance environmental issues in food production and food
of distribution method tends to vary from country “quality” should not be the only factors to con-
to country.36 In New Zealand, organic food has in sider.
the past been predominantly distributed directly The purpose of this review is to evaluate stud-
from farmers to consumers and via health food ies that set out to compare the nutritional value,
shops. It is only comparatively recently that some sensory quality, and food safety issues of organi-
supermarkets have taken an interest in stocking cally and conventionally produced food. While
organic products, largely because of difficulties both consumers and food producers appear to
in securing regular supplies and also because sig- find these particular issues of increasing interest
nificant consumer interest has only developed quite from food choice and food marketing perspec-
recently. tives, respectively, it is important to acknowledge
that a discussion of these issues only provides a
very limited comparison of organic and conven-
D. Comparisons of Organic and tional food production systems. In order to fully
Conventional Food Production Systems evaluate the advantages and disadvantages of both
systems of food production, a far broader discus-
A wide range of factors has been investigated sion of the issues mentioned above is necessary.
in studies comparing organic and conventional
food production systems, including economics,
crop yields, agronomic factors (soil chemical prop- II. THE NUTRITIONAL VALUE OF
erties, soil physical properties, soil microbiologi- ORGANICALLY AND CONVENTIONALLY
cal activity, pest and disease burdens etc), farm GROWN FOOD
management practices, product quality (nutritional
value, taste, shelf life), environmental impacts, A. Introduction
biodiversity, farm nutrient inputs and social, trade,
and political issues associated with food produc- A large number of studies have been reported
tion.2,37-54 Clearly, in order to make a valid com- that attempt to investigate if there is a difference
parison of the two production systems a broad in the nutritional value of organically and con-
perspective needs to be taken. Food quality and ventionally grown food. There is considerable
what is meant by quality in the context of organic variation in the types of studies and study designs.
food production systems is one area that has re- However, the majority involve one of four main
ceived much attention in the debate on differ- approaches:
ences between organically and conventionally
produced foods.37,55-60 Many people involved in 1. The chemical analysis of organic and con-
the organic food industry believe that a broad ventional foods purchased from retailers
perspective concerning food quality is required in 2. The effect of different fertilizer treatments
order to ensure the provision of a sustainable food on the nutritional quality of crops
supply in years to come. Hence, a number of areas 3. The analysis of organic and conventional
have been identified as important to consider — foods produced on organically and conven-
authenticity, functional properties (how well food tionally managed farms
is suited to specific purpose — storage, cooking, 4. The effect of organic and conventional feed/
and processing quality), biological factors (how foods on animal and human health (pre-
food interacts with the body’s functioning), nutri- dominantly reproductive health)
tional value, sensory characteristics, ethical is-
sues, environmental issues, and social issues in Within each of the four approaches, it is ex-
relation to production and distribution.16 Recently tremely difficult to compare findings because of
it also been argued that in the future eating locally the varying study designs. In addition, the studies
4that focus on the effect of fertilizer type on nutri- to verify that organically labeled products were,
tional value and those that involve the analysis of in fact, from organic production systems and also
foods purchased from retailers do not enable clear no details about the sampling system were re-
conclusions to be made about the impact of or- ported.
ganic and conventional production systems on Some researchers argue that the best way to
nutritional value. In the former study type only evaluate what nutrients consumers are actually
one (although important) aspect of production is getting is to purchase the food, as they would
considered, while in the latter type little or noth- from the retailers. However, this approach does
ing is known about the origin of the foods ana- not allow such variables as maturity at harvest,
lyzed. However, given that fertilizer treatment freshness, and cultivar to be controlled at all (as
studies are cheaper and easier to carry out than well as any growing conditions), so these vari-
whole farm comparison studies, it is not surpris- ables could well confound any apparent differ-
ing that this approach is commonly taken. While ences in nutritional value.
these studies do contribute to fundamental knowl- A recent study commissioned by the Organic
edge of fertilizer effects, they do not provide clear Retailers and Growers Association of Australia
answers on the effect of different farming sys- (ORGAA) claimed that organic vegetables (beans,
tems on nutritional value of crops. Potentially tomatoes, capsicum, silverbeet) sampled from a
more useful information about any differences in certified organic farm may have considerably
nutritional value would be obtained from the analy- higher minerals content than similar foods pur-
sis of food produced from organic and conven- chased from a supermarket.64 Although ORGAA
tional farms, because the effect of whole systems recognize that this is only one very limited study,
of production (which are documented) on nutri- they believe that the very much higher levels in
tional value are essentially being evaluated. Ani- organic food justify further study in a more rigor-
mal and human health studies, together with in- ous fashion. It is interesting to note that there
formation on food composition, could ultimately were no major differences in vitamin C and caro-
reveal the clearest answer. Such studies are, of tene levels in the crops studied.
course, the most difficult and expensive to per- Perhaps a more worthwhile approach to take
form. Food composition data alone do not reveal with this type of study would be to identify retail
much about how foods may be digested and me- suppliers (i.e., growers) of organic and conven-
tabolized in the body. tional produce that are located in a similar area
In the following sections a number of studies and establish an experimental protocol that would
are reviewed. Since some of the early studies (pre enable farming systems to be well documented as
1960) have not been reported in sufficient detail well as harvest date, distribution chain condi-
and/or have used questionable analytical meth- tions, storage conditions at the retailer, etc. In this
ods, the focus of the review is on more recently way some of the variables could perhaps be con-
published work. trolled and so any differences in the nutritional
composition of produce purchased at the retail
stage could be more accurately evaluated. How-
B. Retail Purchase Comparisons ever, even with a more elaborate protocol such as
this, there would need to be a large number of
Although only a small number of studies have studies carried out in different areas in order to
taken the approach of measuring nutritional value make any generalized conclusions.
of products purchased from retailers, it is often
these studies that gain media attention (Table 1).
For example, Smith67 is periodically quoted in the C. Fertilizer Treatment Comparisons
popular media as proving that organic food is
more nutritious than conventional food. The study It is well known that the application of fertil-
design precludes any such conclusions being made izers in crop production will affect the composi-
because it appears that there was no effort made tion of plant material.69-75 Considerable emphasis
56
Table 1
Summary of Studies Comparing the Nutritional Value and General Quality of Organically and Conventionally Grown Food
as Purchased from Retailershas been placed on the effect of nitrogenous fer- and millet were studied by both analyzing the
tilizers on crop nutritional value and yield.76-88 chemical composition of the crops and by feeding
The majority of studies indicate that the higher the crops to animals.94 The author claimed that
the amount of nitrogen available to the crops, the wheat grown in the manure had higher (10 to
higher its uptake and as a consequence the higher 17%) vitamin A levels than that grown in the
the nitrogen and nitrate contents of the crop. chemically fertilized soil and that the “manured”
Whether the use of organic fertilizers results in millet had 15% higher levels of vitamin B com-
different responses to that of inorganic sources of pared with that grown on soil treated with chemi-
nitrogen has been studied frequently (see later). cals. In addition, growth was considered to be
A number of other factors may also affect better in animals fed the “manured” wheat. It is
plant composition, and for this reason it is often clearly difficult to ascertain the reliability of these
difficult to isolate the effect of fertilizers. The results given the lack of statistics and the unclear
main factors that can influence the nutritive value way in which the studies were reported.
of crops include:48,69,71-73,89,90 El Gindy et al.95 investigated the effect of
fertilizer treatment, variety and soil type on the
1. Genetics (i.e., plant crop and cultivar) protein, and mineral content of wheat. This study
2. Environment is of particular interest because it is one of few
• soil type and structure that have used appropriate statistical techniques
• fertilizer type and application method to explore the relative importance of fertilizer
• climate - light, temperature, rainfall, hu- treatment, soil type, and plant variety on crop
midity composition. It was found that plant variety had
• soil microbial populations more influence on protein and overall mineral
• management practices — e.g., crop rota- content than either fertilizer treatment or soil type,
tion, use of pesticides, irrigation, growth although there were significant interactions be-
regulators, cultivation practices tween soil type and fertilizer treatment for some
3. Post-harvest practices nutrients.
• harvest time (crop maturity) Table 2 presents a summary of some of the
• handling and storage more recent studies that have compared the effect
• processing methods and conditions of inorganic and organic fertilizers on the nutri-
tional value of crops. The most common crops
Studies investigating the effect of inorganic investigated are carrots, lettuce, potatoes, and leafy
and organic fertilizers on crop composition have green vegetables, particularly spinach. A number
been carried out for some time and researchers of studies have analyzed crops for a range of
have made varying attempts to control some of minerals; however, the most common nutrients
these other factors that could affect nutritional analyzed are vitamin C, carotene, and nitrate. In
value. In addition, sampling protocols and ana- addition, dry matter has been reported frequently.
lytical methods used (particularly in the earlier The majority of studies have used an accepted
studies) may have also affected nutrient concen- experimental design (randomized block with rep-
trations reported. Consequently, interpretation can licates), although there are a number that have not
often be difficult. A number of early studies found appeared to pay much attention to experimental
no significant difference in the nutritional value design.96,118 In fact, in a few cases authors have
of crops fertilized with manure-based composts claimed significant differences when no statisti-
compared with those treated with inorganic fertil- cal techniques have been used at all.96,103,109,116
izers.91-93 In these studies, vitamin C in potatoes, The studies by Schuphan116 are frequently quoted
vitamin A in sweet potatoes, and vitamin B1 in in support for increased nutritional value of or-
wheat and barley were investigated. In a much ganic crops.47 The studies were conducted over a
larger and comprehensive study, the effect of fer- 12-year period and are among the longest in du-
tilizer treatments (control vs. manure vs. chemi- ration reported to date. Although some of the
cal fertilizers) on the nutritional value of wheat claims of increased nutrient levels from organic
78
Table 2
Summary of Studies Comparing the Nutritional Value of Food Grown Using Different Types of Fertilizers9
10
Table 2 (continued)11
12
Table 2 (continued)fertilizers may be justified, some may not because treatments on carrot quality. In other words, the
the author only reports the percentage increases effects of specific fertilizer types and dosage
for some nutrients rather than reporting any proper strongly depends on local conditions, and so re-
statistical tests for significance. It is also interest- sults from one location cannot necessarily be ex-
ing to note that in this particular study, results pected to be repeated in another.
varied depending on the soil type.116 There have Overall, the fertilizer comparison studies sug-
been numerous other reports by Schuphan that gest that at least in some situations the use of
review a number of studies.124,125 One of the top- organic fertilizers may result in lower nitrate lev-
ics discussed is the effect of nitrogen on crop els of some crops and some cultivars than when
composition,124 and it is claimed that increasing using the more soluble mineral fertilizers. Whether
nitrogen application may decrease dry matter, total this trend would continue consistently under long-
sugar, vitamin C, essential oils, methionine, and a term management is not clear. Certainly different
number of minerals. In addition, nitrate levels in climatic conditions could well influence nitrogen
plants may increase in response to increasing ni- and nitrate content as well as fertilizer treatments.
trogen applications. A number of studies are ref- With regard to the effect of fertilizer type on
erenced in support of these claims, although the mineral and vitamin content of crops, the study
details are often difficult to verify. designs and results are too variable to make any
The studies by Vogtmann and colleagues120,121 definite conclusions.
are also often quoted in support of nutritional
benefits of organic fertilizers. Certainly some of
the container, field trials, and farm comparison D. Whole Farm Comparisons
studies support the claimed lower nitrate levels in
produce grown using organic fertilizers compared Table 3 presents a summary of studies that
with mineral fertilizers. However, there is some have compared the nutritional value of food pro-
variation among the findings, with cultivar type duced from conventional and organic farming
and season being identified as two variables that systems. Some researchers have attempted to con-
may also influence crop composition. trol variables such as farm location, soil type,
The study by Lieblein38 is one of the better cultivar, and maturity at harvest, in an effort to
designed, analyzed, and reported studies investi- reduce the number of potential factors affecting
gating the effects of fertilizer treatments on the nutritional value.126,127,130,132,136,138 Farm compari-
quality of carrots. Three factors were investigated: son studies have the advantage that effects of
fertilization (four levels of organic and mineral whole farming systems are compared, although
fertilizer each plus control), location (2), and year they commonly preclude the relative importance
(2). The field experiment was conducted on farms of individual factors on nutritional value from
that had been managed biodynamically for the being clarified because few researchers have used
previous 5 years. Rainfall and air temperature appropriate experimental designs and statistical
were recorded at the two locations (which had methods. The studies vary in duration with only a
different soil types). It was found that carrot nitro- small number of studies being carried out for
gen levels increased with increasing application more than 3 years.58,139 However, some of the
of nitrogen from mineral fertilizers only, but that studies were carried out on farms that had been
this trend was not consistent over the 2 years and managed organically or conventionally for a con-
at both locations. At one location only, organic siderable period of time.
fertilizers resulted in a lower nitrate content in the As with the fertilizer treatment studies, the
carrots compared with the carrots grown using results from the farm comparison studies are also
mineral fertilizer. There was no effect of fertilizer highly variable. It appears that the farm compari-
type on the carotene content of the carrots. Mul- son studies have generally shown fewer signifi-
tivariate analysis revealed that location was a cant differences in the nutritional value of organi-
particularly important variable affecting any dif- cally and conventionally grown food than the
ferences between organic and mineral fertilizer fertilizer treatment studies. This could be because
1314
Table 3
Summary of Studies Comparing the Nutritional Value of Food Produced from Organic and Conventional Farms15
of the interaction of a larger number of variables levels in organic crops.126,127,130,138 Because vita-
affecting nutritional value when comparing whole min C content is readily affected by maturity at
farming systems than when comparing fertilizer harvest, storage conditions (e.g. temperature), sur-
treatments only (particularly when in fertilizer face bruises, and presence of oxygen, irrespective
experiments efforts have been made to control of farming system,142 it is not surprising that there
some variables). is considerable variation in results both within
A relatively consistent finding appears to be and among studies.
that organic products tend to have lower nitrate The study by Bear et al.143 is frequently cited
levels.58,128,130,132 A finding of a higher nitrate level in support of higher nutrient levels of organically
in organic milk was subsequently thought to have grown food. Although this study demonstrated
arisen from contamination from equipment clean- that the mineral content of crops from commer-
ing agents.129 It is extremely difficult to identify cial farms can vary considerably with location
any other trends from the results of these farm and soil type, it did not compare the effect of
comparison studies, although of the four studies organic and conventional farming systems on
that analyzed protein in wheat/maize, the protein nutritional value.144
level in conventional wheat was either higher or
the same as in organic wheat.58,136,137,139 It has
been suggested that lower protein levels in or- E. Animal Feeding and Human Health
ganic wheat may be caused by lower nitrogen Studies
availability under an organic farming system, al-
though this could readily be modified with vari- Most of the studies that have compared the
ous organic production techniques.137 Storey et consumption of organically and conventionally
al.140 have also reported a low protein content of grown feed on animal health were carried out
organically grown wheat from a study investigat- some time ago and, frequently, detailed reports of
ing the suitability of wheat cultivars for an or- studies are lacking. Hodges and Scofield145 cite
ganic production system. In contrast, as discussed studies that claim that the intensive use of mineral
earlier, McCarrison and Viswanath94 claimed or- fertilizers may lead to increased infertility in cattle.
ganic wheat to be nutritionally and metabolically In addition, Gottschewski (1975) and Staiger
superior. (1986) (see Vogtmann146) report improved repro-
The carotenoid content of crops has been ana- ductive health from the consumption of organi-
lyzed frequently in both fertilizer treatment and cally grown feed. Rabbits given biodynamic feed
farm comparison studies. There is some evidence had more embryos, had a higher number of off-
that higher applications of nitrogen may decrease spring born, and were less susceptible to infection
beta-carotene levels132 and also that the use of some than those rabbits given conventionally grown
pesticides in conventional production systems may feed. Because both the biodynamic and conven-
cause lower beta-carotene levels in some crops,134 tional feeds had a similar composition, the study
although other studies are not in agreement. For suggested that factors other than feed composi-
example, Giannopolitis et al.141 reported that an tion may be causing differences in biological per-
application of two herbicides to lettuce resulted in formance. What these factors may be is not clear.
no change in carotene content in 1 year of the trial Another study (see Vogtmann146) reported lower
but decreased carotene levels in a subsequent year. mortality of newborn rabbits for those fed organi-
However, it was noted that the rainfall was higher cally grown feed compared with those given con-
in the second year, which may have facilitated root ventional or commercial feed but no differences
absorption of the herbicides. in fertility. In contrast, however, a number of
Demonstration of differences in the vitamin studies report no benefits on health from the con-
C content of organic and conventional foods have sumption of organically grown feed.92,93,147-149
not been consistent, with some studies reporting However, some of these studies121 have been criti-
higher levels in organic crops58,127,128,132,133 and cized over the use of unbalanced diets given to the
others reporting no significant differences or lower test animals.145
16As with the other types of studies investigat- One of the few studies attempting to evalu-
ing the nutritional value of organically and con- ate the effect of organically grown food on
ventionally grown food, the overall findings of human health was that reported by Schuphan.124
the animal experiments are variable. The long- Although some benefit of organically grown
term Haughley experiments150 suggest that or- food on infant weight and blood measures was
ganically grown feed may have some benefit for reported, the details of this work are not readily
animal health and performance (for example, in- available. More recently there has been some
creased milk production from organically fed interest in semen quality of men involved in the
cows), although it has been suggested that ani- organic food industry (farmers, consumers)
mals were placed in “artificial conditions” in the compared with that of men in other industries
experiments and so the findings may not be gen- or workplaces.158-161 These studies have either
eralizable to other situations.150,151 These experi- attempted to correlate organic food consump-
ments and others94,152-155 could also be criticized tion/dietary pesticide residue levels with semen
over the use of feeds obtained from various fertil- quality or compare semen quality of organic
izer treatment studies rather than from organi- farmers/consumers with nonorganic consumers.
cally and conventionally managed farms.156 Abell et al.158 found that organic farmers had a
One of the better controlled studies is that by higher sperm density than three groups of blue-
Velimirov et al.,157 in which organic and conven- collar workers, but offered no particular expla-
tionally produced feed (from neighboring farms) nation for this finding. In contrast, Jensen et
were compared for their effects on rat fertility al.159 found no clear relationship between eat-
over three generations. All the test feeds were ing habits and semen quality, although sperm
chemically analyzed and based on these results concentration was higher in members of or-
the vitamin and mineral composition of the feed ganic food associations than controls. Because
mixture was adjusted so as to avoid both exces- a number of demographic variables were not
sive levels and deficiencies of any nutrient. Twenty controlled in this study, it was suggested that
pairs of rats were fed organic feed and 20 pairs factors other than eating habits could have con-
the conventional feed. There was no significant founded the result.
difference in the pregnancy rate, birth weight, or No significant differences in sperm quality
weekly weight gain of the offspring between the of organic and conventional farmers were iden-
conventionally and organically fed rats. There tified in the study by Larsen et al.160 In this
were significantly fewer offspring born dead in study semen quality was also correlated with
the “organic” fed group than in the “conventional” organic food consumption/dietary pesticide ex-
fed group in the first litter but not in the second posure.161 The farmers were divided into three
litter. Generally, the “organic” fed group had sig- groups according to the amount of organic food
nificantly fewer perinatal deaths than the “con- consumed and dietary pesticide intakes (of 40
ventional” fed group, but a change in feed (with compounds) were estimated. Although the pesti-
respect to year of harvest and growing site) be- cide intake was found to be lower in “high or-
tween the first and second litters of the second ganic food consumption” group, the pesticide
generation was thought to have a favorable effect intake of all groups was estimated to be very
on the rearing performance of the “conventional” low. The group of men who consumed no or-
fed group for the second litter of the second gen- ganic food was found to have a significantly
eration. However, it was found that the number of lower proportion of morphologically normal se-
perinatal deaths was again lower for the “organic” men but for the other 14 semen parameters mea-
fed group than the “conventional” fed group for sured, no significant differences were found. In
both litters of the third generation. Overall, this conclusion, these studies do not provide strong
study indicated that some aspects of rat fertility evidence of any effect of organic food consump-
may be improved from “organic” feed and that tion or pesticide exposure on semen quality, al-
results can often be inconsistent even over gen- though sperm concentration could be further in-
erations within a study. vestigated.
17F. Relevance to Overall Diet and in organically grown foods.163 In contrast, there is
Research Limitations currently an enormous amount of research inves-
tigating the role of such compounds (present in
The majority of studies investigating nutri- conventionally produced food) in common dis-
tional differences between organically and con- eases such as heart disease and cancer.164-166 Stud-
ventionally grown food have limited their analy- ies have shown that increasing nitrogen applica-
ses to a small range of food components such as tion may decrease the level of phenolic compounds
protein, sugars, vitamins, and minerals. This is a in crops, thus making them more susceptible to
very limited approach because nutrient concen- pest and disease problems.163 As well as influenc-
trations do not give any indication of how these ing the growing of these crops, the decrease in
nutrients may be metabolized and hence their phenolic compounds may also have health impli-
bioavailability. Whether there are any differences cations. Given that organic farming systems can
in the bioavailability of nutrients from food grown result in lower nitrate levels in some crops in
using the two production systems has not yet been some situations, it is possible that organically
studied. grown food may offer health benefits that cannot
Another factor that may confound the inter- be measured only in terms of nutrient concentra-
pretation of the nutritional value of organically tions.163,167
and conventionally grown food is whether the Some researchers have attempted to develop
nutrient concentrations are expressed on a dry different methods to compare the quality of organic
weight or fresh weight basis. Although the results and conventional food. Schulz et al.168 have devel-
are variable (see Tables 1, 2, 3), there has been oped a quality index in which 10 parameters (in-
some suggestion that organically grown crops may cluding such factors as dry matter, nitrate, free amino
have a higher dry matter content than convention- acids, protein) were combined in order to make a
ally grown crops.46-48,54 Hence nutrient concentra- more valid comparison between fertilizer treatments.
tions might be more meaningful if expressed on a Although an approach such as this might have some
fresh weight basis. Clearly, the dry matter content merit it appears to have not been pursued in subse-
is another factor that requires further research quent studies. Other very different approaches that
along with investigations on possible mechanisms have been used include copper chloride crystalliza-
that might explain any differences in the dry mat- tion and paper chromatographic methods. In the
ter content of organic and conventional foods. copper chloride crystallization method, the plant
The significance of any possible differences extract is mixed with a copper chloride solution and
in the nutritional value of individual organic and then crystallized under standard conditions. The in-
conventional food products on the overall nutri- terpretation of the crystal patterns focuses on the
tional quality of a person’s diet also needs to be number of centers, the structure and distribution of
considered. Currently, few people are able to con- the needles, the number and kind of branches, and
sume totally organic food because of difficulties the formation of hollow structures. The patterns in
in supply. Also, even if a person’s diet predomi- which salts crystallize from solutions have been
nately consists of organic foods, if the diet is shown to be affected by the presence of impurities,37
unbalanced (high in fat or high in sugar, for ex- and this technique has been used in organic/conven-
ample), any presumed benefits of consuming or- tional food comparison studies. For example, it has
ganic food may be negated by the overall dietary been reported that protein concentration and protein
habits of that person. On the other hand, tentative composition have a significant influence on the crys-
evidence that the nutritional value of our “con- tallization pattern of copper chloride.37 The key dif-
ventional” food supply may be declining could ficulty with this approach is the interpretation of the
mean that organically grown food may offer extra pictures generated,163 although currently work is pro-
benefits yet to be documented.162 gressing using computer-generated images to help
Only recently has there been any research standardize interpretation. Lieblein38 used the cop-
investigating the concentrations of nonnutritional per chloride crytallization method for evaluating
compounds, for example, phenolic compounds, carrots grown under different fertilizer treatments.
18He reported that mineral fertilization resulted in less Given this, it is equally important to assess if
well-formed crystal pictures than organic fertiliza- organic growing methods adversely affect sen-
tion when no significant differences were found in sory properties, because this would certainly dis-
the chemical composition. This could indicate that courage consumers from selecting organic over
mineral fertilization affects the structure of the car- conventional produce.
rot tissue; however, the significance of this is un- A number of studies comparing organic and
clear. Pfiffner et al.114 have also reported differences conventional production methods have included
in the structure of beetroot tissue grown under dif- sensory tests of one form or another along with
ferent cultivation systems when using the copper chemical, agricultural, or nutritional analyses.
chloride crystallization technique. Knorr169 has re- These studies suffer, of course, from the same
ported the use of a circular chromatographic method limitations as other studies in this area, namely,
for distinguishing between plants grown under dif- utilizing a variety of meanings (sometimes un-
ferent fertilizing conditions. Using a “blind” evalu- specified) of “organic” as well as study designs
ation procedure with 50 panelists, differences in that differ in their suitability to make the appro-
chromatograms were seen when the level of nitrog- priate comparisons. Of particular relevance is the
enous fertilizer was changed, indicating that nitrate specification of the source of the organic produce
concentrations could be an important factor when and the extent to which factors such as climate,
attempting to interpret such chromatograms. Clearly, soil, harvest time, and other growing conditions
much more work is required using such techniques were controlled in the comparison. In the studies
if they are to be useful in attempting to distinguish examined, this ranged from sourcing produce from
between organically and conventionally produced “organic producers” (e.g., Porretta173) or “organic
food. farms”138 to highly controlled studies in which
As discussed earlier, comparing the effect of specific details of growing conditions and ap-
organic and conventional farming systems on proaches, for example, fertilizer types, are pro-
nutritional value of crops is inherently difficult vided and the organic and conventional foods are
due to the wide range of factors that can poten- grown under close to identical conditions (e.g.,
tially affect crop composition. While some of Svec et al.118). Such variability clearly militates
these factors can be controlled, others cannot and against finding consistent effects because, even if
so it is unlikely that clear answers will be ob- there are sensory differences due to fertilizer type,
tained in using traditional analytical approaches they may be less apparent than differences due to
such as measuring nutrient concentrations. climate, soil, or other factors.
There is a view, however, that although there
may be multiple factors that differ between con-
III. THE SENSORY QUALITIES OF ventional and organic growing methods, and this
ORGANICALLY AND CONVENTIONALLY makes controlled experiments difficult, this may
GROWN FOOD not matter if we simply want to know about any
consistent differences between conventional and
A. Introduction organic produce that is currently available to the
consumer. In this sense, it might be considered
Among the claims made about organic grow- worthwhile to evaluate studies comparing organic
ing methods is that they produce more flavourful and conventional produce irrespective of differing
(“better tasting”) fruits and vegetables. This is methodologies and definitions of organic produce.
certainly the stated rationale for undertaking a The limitation of this is, of course, that purchased
number of studies in recent years,106,170-172 which products labeled “organic” may not necessarily
have set out to determine the validity of this claim. reflect any of the accepted meanings of the term,
However, even if organic produce is not superior and hence neither positive nor negative findings
in sensory terms, there may be other reasons for can be interpreted with any certainty.
implementing organic farming systems, includ- Another factor that impedes drawing defini-
ing safety and environmental considerations. tive conclusions at times is the incomplete speci-
19fication of both the sensory techniques used (which ganic/conventional differences evident for beetroot
tests, definition of terms, etc.) or the results ob- and carrots, but not for curly kale.130
tained, evident in many studies.120,138,173,174 As one There are two important considerations, re-
example, reporting only that organic tomatoes lating to whether differences are present or not,
had a higher “taste quality” as measured by a which have an impact on interpretations of the
trained panel120 provides little useful information. failure to find a pattern of results in such studies.
All sensory evaluation techniques can be Moreover, these two issues apply not just to
broadly classified into three categories: discrimination tests, but to all of the sensory tests
considered in this review. First, failure to find
1. Discrimination tests, which allow a deter- differences with one fruit or vegetable type or
mination of the presence of differences; variety does not necessarily imply that such dif-
2. Descriptive analysis techniques, which use ferences will not be found in studies of other
trained panels to describe the nature of, and types or varieties. This, of course, will make de-
quantify, any differences that may be present; finitive generic conclusions regarding organic vs.
and conventional produce difficult to make until large
3. Preference/acceptability measures that re- numbers of studies have been undertaken. Sec-
flect relative degrees of liking. ond, interpretations of one, or a few differences in
the context of large numbers of comparisons, such
In the studies examined here, all of these as those reported by Hansen,130 need to be made
approaches are present, and classification along with consideration of the possibility that the posi-
these lines provides a convenient means of sum- tive findings are spurious. This is due to Type 1
marizing the study outcomes. errors, occurring as a result of inflated alpha lev-
els when multiple nonindependent comparisons
are undertaken within the same data set.
B. Discrimination Studies
Valid discrimination techniques such as the C. Descriptive Analysis Studies
triangle test allow straightforward and sensitive
determinations of the presence of sensory differ- As with discrimination tests, those studies
ences, irrespective of the quality of that differ- that have measured responses to specific sensory
ence. Ideally, such studies would be the first step qualities have failed to produce consistent results,
in establishing whether consumers can tell or- and in some cases produced results that are diffi-
ganic from conventional foods, because until dif- cult to interpret. For example, although Weibel et
ferences of any sort can be reliably shown, pref- al.138 found that organic apples had a “higher
erence and descriptive studies might be considered sensory score” than apples from an “integrated
premature. farm”, it is difficult to know what this means.
A small number of studies have opted to use Another study, of Macintosh and Cortland apple
discrimination methods, although their findings varieties, had more clearly interpretable results,
are mixed. Using similarity judgements (which finding no differences for juiciness, sweetness,
can be considered a form of discrimination test- tartness, and off flavor, but concluding that “or-
ing), a group of 18 consumers174 failed to dis- ganically grown” Macintosh apples were more
criminate between organic and conventional car- firm.175
rots. Using a trained panel, which performed a Three studies have compared the sensory prop-
series of triangle tests, Maga et al.106 also failed to erties of organic and conventional tomatoes.
show a difference between organic and conven- Porretta173 showed that a cluster analysis of “all
tional spinach. In contrast, Basker171 did find dif- parameters” (including results of chemical analy-
ferences for spinach and grapes, but not for grape- sis) discriminated between organic and conven-
fruit and sweet corn. A study of several vegetables tional tomatoes. Although the contribution of sen-
found a similar mixed pattern of results with or- sory characteristics to this process was not
20specified, it was noted that conventional products al.176 reported a preference for one organically
had better sensory characteristics, particularly with grown tomato variety but the conventional ver-
respect to color and natural taste. By contrast, sion of another variety.
Vogtmann et al.120 found that organic versions of Given a general failure to report consistent ability
two out of three tomato varieties had higher “taste to discriminate the sensory properties of organic and
quality”, again, a conclusion that is difficult to conventional produce, it is not very surprising that
interpret. A clearer result was obtained by studies of preference also fail to show a consistent
Johansson et al.’s study176 in which trained panels pattern of results. Why then does there seem to be a
assessed organic and conventional tomatoes for a conviction, presumably primarily among regular con-
variety of different attributes. They found no dif- sumers, that organic produce is better tasting? Two of
ferences in acidity, sweetness, and bitterness, but the sensory studies reviewed may give insight into
did find that organic tomatoes were less firm, less this. It has been demonstrated that labeling associated
juicy and redder. This same group172 also com- with a food can create expectations regarding its
pared organic and conventional carrots from two sensory properties, and ultimately its acceptability.177,178
growing seasons. The results show little in the Both Schutz and Lorenz170 and Johansson et al.176
way of a consistent pattern. In the first year, or- examined the impact of information about growing
ganic carrots had less sweetness, crunchiness, and method on consumer preferences for organic and
flavour, but were harder. There were no differ- conventional vegetables. In both studies, this infor-
ences in aftertaste and bitterness. In the second mation influenced acceptability, in that relative to
year, they were again harder and had less flavor, these same foods unlabeled, products labeled as or-
but more aftertaste. There were no differences for ganic generally showed increases in measures of pref-
sweetness, crunchiness or bitterness. erence. Thus, both studies suggest that consumers
have expectations regarding the superior taste of or-
ganic produce. It may be that this derives either from
D. Preference Studies a rationalization of the higher cost of organic produce
or a belief that chemical fertilizers are more likely to
Is organic produce preferred to conventional impart unacceptable sensory qualities. Important also
produce? As with other types of sensory studies, in the effects of labels on food acceptability is the fact
the research on this issue does not provide an that consumers can bring their actual perceptions and
unambiguous answer. Using a consumer group, preferences into line with such expectations.177 Hence,
Schutz and Lorenz170 found no differences in rat- such beliefs may be reinforced by repeated consump-
ings of liking between organic and conventional tion of organic produce.
lettuce and green beans. On the other hand, or- One other reason for the popular belief in the
ganic broccoli was preferred, as were conven- flavor superiority of organic produce that should
tional carrots. Basker171 undertook preference tests be considered here though is the possibility that
with groups of consumers, finding that organic organic produce might be consumed in a more
bananas were preferred, as were conventionally optimal state of freshness. This could be due to
grown mangoes and juice from conventionally any of the following reasons:
grown oranges. There were no differences in pref-
erence for grapefruit, grapes, corn, spinach, car- 1. Some organic producers may be distributing
rots, or tomatoes from the two sources despite, in primarily locally, rather than using more
the case of spinach and grapes, there being per- elaborate distribution systems;
ceived differences. Svec et al.’s118 small panel 2. There may be a greater emphasis on more
(12) preferred the color and texture of conven- natural forms of ripening, prior to harvest;
tional potatoes, but there were no differences in 3. Organic farming may use different varieties
liking for appearance or flavor. With tomatoes, of the same food than conventional farming.
the panel showed a preference for the organic
product on all of these sensory attributes. Using a At least in the case of the first two factors, even
much larger group of consumers, Johansson et those systematic studies making well-controlled
21comparisons, may fail to take into account com- pesticide residues, as a key reason for consuming
monly used distribution and ripening practices. organically grown food. Given the prohibition of
chemical pesticides in an organic farming system,
it is a reasonable assumption that organically
E. Conclusion grown food will in general contain lower levels of
pesticide residues than conventionally grown food.
Overall, then, what can be concluded from However, there have been very few studies car-
these studies? The simplest statement would be ried out considering this question.
that there is yet to be convincing evidence that
organic produce differs in sensory terms from
conventional produce, let alone that there is some 1. Residues in Organically Grown Foods
taste advantage. However, as noted earlier, with-
out considerably more well-controlled research, it In a review of the risks of consuming organi-
cannot be proposed that such differences may not cally grown food,179 reference is made to a Swed-
be apparent for some foods under some growing ish study in which there were no detectable resi-
conditions. Moreover, as noted above, the impact dues in organically grown carrots, iceberg lettuce,
of distribution practices needs to be considered. tomatoes, and strawberries. In comparison, 17%
This conclusion is supported by a previous of conventionally grown carrots and 50% of straw-
overview of literature published primarily in Ger- berries had detectable residues, while conven-
man up to 1995. Woese et al.46 reviewed a large tionally grown iceberg lettuce and tomatoes had
number of studies covering a variety of agricultural no detectable residues. The concentrations of resi-
products, as well as foods made from organically dues in the conventionally grown carrots and straw-
grown produce (e.g., bread). In reviewing those berries were well within the allowable limits.
studies that dealt with the sensory aspects of or- Internationally there is little accessible data
ganically grown foods, the authors note that there on pesticide residues in organic foods. In New
was no clear evidence for sensory differences be- Zealand, the main potential source of data on
tween organic and conventional versions of pota- residues (if any) present in organically grown
toes, vegetable or vegetable products, or apples. food is Bio-Gro New Zealand, the main organic
They did note “greater fluctuations.... in quality certification agency. Typically, however, residue
characteristics” (p. 256) for bread produced with testing of food products may only be required by
organically grown grain, although they suggested Bio-Gro New Zealand when a grower first be-
that this might be due to different baking methods comes certified and thereafter only when auditors
or recipes. The review also examined studies that make special requests. It is considered that if the
compared produce from animals that had been fed property is being managed according to the stan-
organically grown feed to those conventionally dards, end-point routine pesticide residue testing
fed. These products included milk and dairy prod- is not required. It is important to note that like
ucts, meats, eggs, and honey. In none of the studies most certifying agencies, Bio-Gro New Zealand
reviewed was there evidence for differences in the recognizes that some pesticide residues can be
sensory properties of products associated with or- widely present in the environment, particularly
ganic and conventional growing methods. the more persistent organophosphates and orga-
nochlorines, and so Bio-Gro New Zealand does
not guarantee certified organic produce to be to-
IV. FOOD SAFETY ISSUES tally free of residues.
Some producers and larger companies, how-
A. Chemical Residues in Organic and ever, do a certain amount of residue testing of
Conventional Foods organic food products, often in order to satisfy
overseas markets or be able to verify the low or
As discussed earlier, consumers frequently no residue content of their products. For example,
cite health concerns, and specifically low or no from 1998 to 2000 Zespri International tested
22You can also read
