Carcass and meat characteristics of the Nile
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Journal of the Science of Food and Agriculture J Sci Food Agric 80:390±396 (2000)
Carcass and meat characteristics of the Nile
crocodile (Crocodylus niloticus)
Louwrens C Hoffman,* Peter P Fisher and James Sales
Department of Animal Sciences, University of Stellenbosch, Private Bag XI, Matieland 7602, South Africa
Abstract: Seven Nile crocodiles (Crocodylus niloticus) of 1300 mm length were slaughtered in order to
established baseline values for component yields and expected percentage of lean meat, fat and bone
for this species. The skin presents nearly 20% of the live weight of the Nile crocodile, while a dressing
percentage of 56.5% was derived. The tail realised 18 and 33% of the live weight and empty carcass
weight respectively. Values of 60.8, 12.2 and 26.6% of carcass weight were obtained for total lean meat,
fat and bone respectively. A pH value of 6.5 at 24 h post-mortem in both tail and leg muscles and a
decreasing pH towards 48 h post-mortem illustrated that rigor mortis is still not complete when
crocodile carcasses are processed. While fat content differed statistically (P < 0.05) from 91.1 g kgÿ1 in
raw torso samples to 29.4 g kgÿ1 in raw neck samples, protein content was relatively constant around a
mean of 220.8 g kgÿ1 in raw meat. Cooking did not have any in¯uence of practical value on proximate,
amino acid or mineral composition. Crocodile meat is characterised by a lower iron, magnesium and
sodium content than either beef or chicken. Of the total fatty acids present in the tail samples, 37.7%
were saturated, 51.1% monounsaturated and 10.7% polyunsaturated. Oleic acid was predominant
(43.1%), whilst palmitic acid (25.4%), stearic acid (9.9%) and linoleic acid (9.1%) were also present in
high concentrations.
# 2000 Society of Chemical Industry
Keywords: Nile crocodile; carcass components; yields
INTRODUCTION believed that eating crocodile meat would be an
Crocodile (Crocodylus niloticus) farming, practised for exciting, adventurous and possibly risky experience.5
the past 25 years in southern Africa, started in In Zimbabwe a marketing strategy based on these
Zimbabwe as early as 1963 when a policy was adopted presumptions is used successfully by hotels, particu-
to allow licensed crocodile farmers to collect a larly those situated in game parks. Although not
prescribed number of eggs from the wild and incubate documented, the restaurants in South Africa use a
them arti®cially to be slaughtered later and sold (skins) similar strategy, focusing primarily on international
on the international market.1 In South Africa, croco- travellers who wish to experience Africa, as their
dile farming started in the late 1960s and by 1992 consumer target group.
there were over 40 established farms operating.2 The No data pertaining to the carcass and meat charac-
traditional focus of the crocodile industry has been on teristics of the Nile crocodile (C niloticus Laurenti
producing skins used in the production of high-quality 1768), the only crocodile species farmed in Africa,
fashion accessories.3 With the increase in production could be accessed. The present study was therefore
costs in South Africa, crocodile farmers have had to conducted in order to establish baseline values for the
look at alternative means of increasing the pro®tability yields and chemical composition of body components
of their enterprise. Two major sources of income have from the Nile crocodile
been incorporated into the major component of skin
production, namely tourism4 and meat production.
Presently, in South Africa, most of the crocodile meat MATERIALS AND METHODS
produced is either exported or sold to the restaurant Slaughtering, pH measurements and carcass
trade or used as unprocessed crocodile feed on the evaluation
farm. Seven crocodiles in the age range 33±34 months from a
In Australia, where two crocodile species (C porosus commercial crocodile farm in South Africa were
and C johnstoni) are farmed for their skins and meat, a slaughtered using standard procedures, namely by
marketing survey showed that consumers generally shooting through the brain with a 0.22 calibre ri¯e and
knew little about the product (crocodile meat) and severing the spinal cord posterior to the head. In this
* Correspondence to: Louwrens C Hoffman, Department of Animal Sciences, University of Stellenbosch, Private Bag XI, Matieland 7602,
South Africa
(Received 14 May 1999; revised version received 27 September 1999; accepted 14 October 1999)
# 2000 Society of Chemical Industry. J Sci Food Agric 0022±5142/2000/$17.50 390Crocodile meat
Component Weight (g) % of live weight % of carcass weight
Live weight 8316 618.0
Body components
Empty carcass weight 4695 329.8 56.5 1.50
Blood 109 52.9 1.3 0.63
Skin 1646 132.6 19.8 0.59
Head 521 37.4 6.3 0.22
Feet 165 19.8 2.0 0.26
Lungs 54 13.5 0.7 0.14
Liver 150 18.7 1.8 0.14
Gutfat 197 62.7 2.3 0.60
Gastrointestinal tract 681 197.5 8.2 2.16
Empty carcass components
Table 1. Live weight, carcass weight and weight of Tail 1531 119.9 18.4 0.90 32.6 0.82
carcass components of the Nile crocodile Legs 788 54.8 9.5 0.43 16.8 0.82
(Crocodylus niloticus) (length 1301 24.7 mm)
Torso 1830 143.0 22.0 0.79 39.0 0.67
obtained from a commercial producer (mean SD,
Neck 560 60.0 6.7 0.48 11.9 0.97
n = 7)
farming enterprise the crocodiles were stunned in their 50 min. Thereafter the samples, still in the bags, were
pen, removed and the neck vertebrae were severed cooled under running water at 25 °C for 40 min,
immediately thereafter. After washing, the crocodiles removed from the bags and reweighed. Cooking loss
were left overnight in a cool room at 0±3 °C to bleed. was measured as the amount of ¯uid loss expressed as
Measurements of pH were obtained using a a percentage of original (wet) weight. The Warner
calibrated (standard buffers at pH 4.0 and 7.0) Crison Bratzler shear force values were determined by taking
506 portable pH meter at a depth of 2.5 cm at 1, 2, 4, ®ve readings on each of the tail samples and were
8, 12, 16, 24 and 48 h post-mortem. Two measure- measured as maximum shear force (kg per 1.27 cm
ments were noted, one in the hind leg and the second diameter). Only tail samples were analysed for shear
in the tail (2 cm from the tail attachment to the torso). values, as the meat samples derived from the other
A ®ne slit was made in the skin for the insertion of the body components were too small for the correct
pH electrode; the ®nal pH (48 h) was measured on the procedures as described by Bratzler.7
skinned carcass.
The next morning the crocodiles were dressed Chemical analysis
according to the conventional slaughtering procedures Moisture content by drying a 2.5 g sample at 100 °C to
used for crocodiles in South Africa.6 Initial cuts were constant weight, ashing at 500 °C for 5 h, protein
made extending across the neck immediately behind content by the block digestion method and ether-
the skull, along the edge of the lower jaw, along the extractable fat content by solvent extraction8 were
back to the bony neck scales (known as the nuchal determined on the minced samples of lean meat from
cluster), down the sides of the upper ¯anks, but leaving the tail, neck, torso and legs.
two distinct rows of enlarged dorsal scales on the belly Amino acids were determined on freeze-dried, fat-
side of the skin. Additional cuts extending along the free samples from the raw and cooked tails by ion
tops of the legs and along the lateral base of the tail exchange chromatography of the acid-hydrolysed
were also made. The skin was then removed. There- protein. Samples of each muscle were hydrolysed with
after the crocodiles were eviscerated. Skins, body 6 M HCl in a sealed tube under N2 for 22 h in an oil
components and empty carcasses were weighed. bath at 110 °C. A Beckman Model 6600 amino acid
Empty carcasses were divided into tails, legs, torsos analyser was used for separating amino acids using
and necks and subdivided into meat, fat and bone. sodium citrate buffers.
Tails were obtained by cutting across the base of the A dry ashing procedure was used to prepare the
tail just behind the hind legs. Legs were obtained by freeze-dried raw and cooked tail samples for mineral
severing their joints at the attachment to the body. The analysis. Sodium, potassium, calcium, magnesium,
neck consisted of the portion between the head and the phosphorus, iron, copper, zinc, manganese and
front legs. After removal of the neck the rest of the aluminium contents of the digestates were determined
empty carcass was categorised as torso. by direct current plasma emission spectrometry.9
The ether-extracted total lipids from raw tail
Physical characteristics samples were analysed for fatty acids. Fatty acid
Lean meat samples were taken from the tail, neck, methyl esters were saponi®ed and prepared in metha-
torso and legs to determine cooking loss, while shear nolic (5%) sulphuric acid at 70 °C. Esters were
force values were also determined on tail samples. The separated on a Varian Model 3300 gas chromatograph
samples were weighed, placed in polyethelyne bags, equipped with a ¯ame ionisation detector and a glass
vacuum sealed and placed in a water bath at 75 °C for column (2 m 5 mm id) packed with Chromosorb
J Sci Food Agric 80:390±396 (2000) 391LC Hoffman, PP Fisher, J Sales
Component Weight g % of component % of live weight % of carcass weight
Meat
Tail 968 72.4 63.3 3.33 11.7 0.63 20.6 1.04
Legs 532 40.8 67.5 2.48 6.4 0.20 11.3 0.33
Torso 964 124.5 53.5 3.48 11.5 0.72 20.5 1.39
Neck 392 43.3 70.0 2.52 4.7 0.29 8.3 0.63
Total 2855 260.6 34.3 1.12 60.8 2.28
Fat
Tail 304 56.2 19.7 3.14 3.7 0.69 6.5 1.08
Legs 34 12.4 4.3 1.25 0.4 0.12 0.7 0.22
Torso 225 33.2 12.3 2.11 2.7 0.50 4.8 0.83
Neck 9 5.3 1.6 0.90 0.1 0.06 0.2 0.10
Total 572 85.5 6.9 1.08 12.2 1.68
Bone
Tail 244 33.3 15.9 1.32 2.9 0.22 5.2 0.42
Legs 238 31.0 30.3 4.74 2.9 0.46 5.1 0.7
Table 2. Weight and percentage of knife-
Torso 611 62.9 33.4 2.27 7.4 0.64 13.0 0.83
separable lean meat, fat and bone of the Nile
Neck 157 19.3 28.0 2.02 1.9 0.22 3.3 0.40
crocodile (Crocodylus niloticus) (mean SD,
Total 1249 105.0 15.0 1.06 26.6 1.23
n = 7)
Table 3. pH values at fixed times post- RESULTS AND DISCUSSION
mortem of the tail and leg meat in cooling
Carcass characteristics
crocodile carcasses (mean SD, n = 7)a
Live weight, carcass weight and weights of the
Time h Tail Leg different body components removed during the
1 6.88b 0.185 7.15bc 0.296 slaughtering process are presented in Table 1.
2 7.21a 0.257 7.54a 0.333 The dressing percentage (carcass weight as a
4 7.26a 0.110 7.54a 0.240 percentage of live weight) of 56.5% was lower than
8 7.28a 0.232 7.41ab 0.301 the value of 63.3% derived by Moody et al 12 for
12 7.28a 0.250 7.01c 0.349 Alligator mississippiensis of similar length (1400 mm).
16 6.84b 0.251 6.47d 0.365 The percentage of skin on a live weight basis in the
24 6.67b 0.258 6.53d 0.186 present study was therefore considerably higher than
48 6.28c 0.176 5.83e 0.154 the value of 15% stated by Moody et al. 12 However,
a
Column means with different following differences between studies in regard to killing,
letters differ signi®cantly (P < 0.05). removal of skin and cooling regimes complicate
comparisons between different studies. Moody et
al 12 presented values of 21.1, 8.3 and 27.2% of live
Whp 100/120. Nitrogen was used as carrier gas at a weight for tail, legs and torso respectively for A
¯ow rate of 30 ml minÿ1. The column temperature was mississippiensis of 1400 mm length. The differences in
raised from 180 to 240 °C at 3 °C minÿ1; injector and yield noted between their investigation on alligators
detector temperatures were 220 and 280 °C respec- and the present investigation could be attributed either
tively. Esters were identi®ed by comparison of reten- to species differences or to different techniques used
tion times with those of known standards and oil during the dressing of the carcasses. Presently in South
mixtures. Africa the tail is either marketed as ®llets (consists of
cutting the tail transversely in 10±15 mm thick
portions) to upper-class restaurants or exported to
Europe. The rest of the carcass is deboned and
Statistical analysis exported or sold as a lower-value product in the form
The effect of body component on cooking loss, of goulash-type meat or fed, unprocessed, back to
moisture, protein, fat and ash in raw and cooked meat crocodiles. The latter practice is, however, declining.
and the in¯uence of time on pH in the tail and leg were In Australia the tail is further processed into two
evaluated by analysis-of-variance techniques.10 Indi- products, the tail ®llet and the tail eye. The tail ®llet
vidual animals were used as blocks to remove (M Transversospinalis and M Longissimum dorsi) is
variation, due to differences between animals, from derived from the tail by removal of the vertebral
the error sum of squares.11 Means for individual column, the tail eyes and all excess fat trimmed away.
components and pH at individual time intervals were The tail eyes (M Caudo-femoralis longus) arise from the
compared using least signi®cant differences. Paired t- pelvis and run caudally under the tail on either side of
tests were used to compare pH values between tail and the vertebrae. Alternatively, the tail is marketed as tail
leg, and moisture, protein, fat, ash, amino acid and cutlets where transverse cuts are made through the tail
mineral values between raw and cooked meat.10 and vertebral column for the entire length of the tail.13
392 J Sci Food Agric 80:390±396 (2000)Crocodile meat
Tail Legs Torso Neck Mean
Cooking loss 31.45a 1.61 29.64a 2.48 23.19b 5.35 32.07a 2.33 29.09 3.08
Raw
Moisture 701.7b 18.96 733.9b 7.57 670.7b 22.38 759.5a 13.21 716.4 36.77
Protein 210.9a 8.09 224.0a 9.59 218.8a 7.02 229.4a 7.26 220.8 10.09
Fat 88.5a 27.15 40.4a 11.63 91.1a 16.96 29.4a 8.41 62.3 32.17
Ash 5.9ab 1.55 3.6c 0.79 6.5a 2.00 4.5bc 1.63 5.1 1.85
Cooked
Table 4. Cooking loss (%) and Moisture 650.1b 21.89 682.9a 5.63 647.1b 40.10 679.1a 7.93 664.8 27.08
proximate chemical composition Protein 280.7a 12.54 269.0b 9.63 251.2c 15.70 277.5ab 3.48 269.6 15.50
(g kgÿ1) of the various carcass
Fat 54.4a 25.99 37.6b 12.68 81.9a 57.10 26.4b 5.83 50.1 36.37
components of the Nile crocodile ab b
Ash 6.6 3.40 9.7 6.15 4.2b 0.79 4.2b 1.09 6.2 4.01
(Crocodylus niloticus) (mean SD,
a
n = 7)a Row means with different following letters differ signi®cantly (P < 0.05).
Table 5. Amino acid contents (mean SD for cooked and raw depot is encircled by the Longissimus dorsi muscle,
crocodile lean meat (g kgÿ1 on a fat-free, dry mass basis)
whilst the Caudo-femoralis longus muscle forms the
Amino acid Cooked Raw P(T t) inner muscle of the ventral fat depot. Moody et al 12
noted a similar lipid depot in alligator meat. The
Threonine 3.476 0.090 3.291 0.057 0.0023
Serine 2.847 0.084 2.817 0.066 0.1508
appearance of the meat cuts varied, as also stated for
Glycine 3.781 0.234 4.056 0.239 0.0093 alligators by Moody et al,12 with the meat from the tail
Alanine 4.679 0.093 4.533 0.086 0.0909 appearing white to light pink (as does that of the neck),
Valine 3.824 0.158 3.471 0.087 0.0293 whilst the legs were darker in colour and had small fat
Methionine 2.249 0.068 2.060 0.045 0.0183 depots and substantial amounts of connective tissue
Isoleucine 3.934 0.172 3.557 0.113 0.0463 and tendons (not weighed).
Leucine 7.011 0.235 6.430 0.133 0.0160
Tyrosine 2.847 0.084 2.597 0.076 0.0172
Phenylalanine 3.114 0.130 2.913 0.081 0.0623 pH
Histidine 2.123 0.061 2.147 0.073 0.4609 Mean post-mortem pH decline (over time) in the tail
Lysine 7.588 0.299 6.971 0.152 0.0077 and leg is shown in Table 3. No differences (P > 0.05)
Arginine 6.041 1.626 6.346 1.469 0.6933 were found for mean pH values between tail and leg at
each individual time interval, and the pattern of the
rate of pH decline was similar, except for a decrease
Similar tail cutlets are also marketed within South (P < 0.05) in the leg at 12 h post-mortem that was not
Africa. found in the tail. In both the tail and leg, pH increased
(P < 0.05) at 2 h post-mortem.
Means of lean (meat), fat and bone from the
Although the tail was lighter in colour (almost
different body components are shown in Table 2.
The total lean meat content, on a carcass basis, for the white) compared with the darker brown colour of the
Nile crocodile is somewhat lower than the values of legs, a more scienti®c classi®cation of the muscle types
63±71% stated for broilers, turkeys, beef14 and needs to be done to allow correlation of the rate of pH
ratites.15 decline with muscle type. As crocodiles are poiki-
Of the four major carcass components, the neck lothermic, the rate of pH decline will be strongly
yielded the highest lean content, whilst the tail, which in¯uenced by the environmental temperature. In the
present investigation the reptiles were left to bleed in a
is the main carcass component marketed, yielded
cool room (3 °C), which may explain why they had not
63.3% lean. However, when seen on a weight basis,
the tail had the heaviest lean content (968 g), yet entered rigor mortis at the time of processing (16 h
comprising 11.7% of the live weight and 20.6% of later). Because the pH was still decreasing (P < 0.05)
the carcass weight. Of the carcass components, the tail between 24 and 48 h post-mortem, the non-linear
had the highest percentage of knife-separable fat regression pH 0 ÿ 1 1 ÿ exp 2 time sug-
gested by Kastner et al 16 to describe the pH at time
(19.7%), whilst the neck had the lowest (1.6%). The
0 (b0), the asymptotic minimum pH (b0 ÿb1) and the
fat in the tail mainly consisted of the characteristic fat
rate of pH decline (b2) in muscles would not be
depot found in crocodile tails, namely two interior
suitable to illustrate the pattern of pH decline in the
bands of hard fat that appear circular in cross-section,
present investigation. The time of reaching an
both originating from the caudal vertebrae, the ®rst
asymptotic minimum pH value in crocodile muscles
situated dorsally and the second ventrally. As the
needs further investigation.
spinal column is not situated in the centre of the tail,
the dorsal ring is of a smaller diameter than the ventral
ring. The solid dorsal depot is encircled by the M Physical characteristics
Transversospinalis and M Longissimus dorsi. The ventral Cooking loss was lower (P < 0.05) in the torso in
J Sci Food Agric 80:390±396 (2000) 393LC Hoffman, PP Fisher, J Sales
Species
Nile crocodile a
Component Raw Cooked Beef a Chicken a
Minerals
(mg kgÿ1 of edible portion)
Calcium 68 9.0 67 13.5 60 120
Iron 3b 0.4 4a 1.6 22 9
Magnesium 185 15.3 159 33.3 230 250
Phosphorus 1939 129.2 1674 298.6 2010 1730
Potassium 2423 205.5 2090 243.3 3580 2290
Sodium 282 27.1 237 4 630 770
Zinc 11 2.0 16 3.4 44 15
Aluminium 7 2.1 10 4.5 Ð Ð
Fatty acids
(% of total fatty acids)
Saturated
12:0 0.04 0.019 Ð Ð Ð
14:0 0.75 0.066 Ð 3.2 1.3
15:0 0.27 0.029 Ð 0.6
16:0 25.38 3.008 Ð 26.9 26.7
18:0 9.89 1.700 Ð 13.0 7.1
20:0 1.38 0.530 Ð Ð Ð
Monounsaturated
16:1 w7 5.85 0.184 Ð 6.3 7.2
18:1 w9 43.05 2.056 Ð 42.0 39.8
20:1 w9 2.19 0.811 Ð tr 0.6
Polyunsaturated
18:2 w6 9.05 6.898 Ð 2.0 13.5
20:5 w3 0.48 0.007 Ð tr 0.7c
22:5 w3 0.31 0.035 Ð tr tr
22:6 w3 0.90 0.021 Ð tr 1.0
a
Row means with different following letters differ signi®cantly (P < 0.05).
b
Table 6. Mineral and fatty acid composition of Refs. 22 and 23.
c
crocodile tail meat (mean SD, n = 7) in 20:4 20:5 = 0.7.
comparison with beef and chicken tr, less than 0.1.
comparison with the other body components (Table investigation (Table 4) showed similar crude protein
4). but higher total fat (and a correspondingly lower
Compared with other species, the cooking loss moisture) and lower ash contents than those noted for
values are only fractionally higher than the 25.6± alligator meat (21.2, 1.2, 76.3 and 1.3% respectively)
28.2% reported for pork17 but lower than the 35.5% by Moody et al. 12 While moisture, fat and protein
found for ostrich18 when determined using the same contents of crocodile meat are in the ranges 695±765,
procedure. Shear force values of the tail samples 12±95 and 195±234 g kgÿ1 respectively, summarised
(4.35 1.45 kg per 1.27 cm diameter) are similar to for raw mammalian and poultry meat, crocodile ash
those for other species such as beef,19 pork17 and content is below the value of 10±15 g kgÿ1 reported by
ostrich18 (4.3, 3.2 and 3.35 kg per 1.27 cm diameter Forrest et al. 20
respectively). These two factors, combined, could For a comparison of the effect of cooking on the tail
in¯uence consumer perspectives, as they both hold amino acid composition, the data were analysed on the
direct correlation to juiciness and toughness. defatted, dried samples, thereby removing any bias
that might occur owing to the moisture and lipid loss
Chemical composition that took place during cooking (Table 5). When
In both raw and cooked samples the neck presented a expressed in this manner, all the amino acids analysed,
high (P < 0.05) protein content, while the tail and legs with the exception of serine, alanine, phenylalanine,
were characterised by a high (P < 0.05) fat content. histidine and arginine, differed statistically (P < 0.05)
Fat and ash contents were lower (P < 0.05) in cooked as a result of cooking. Of these, all the amino acids
than in raw torso samples, while ash was lower analysed, with the exception of glycine, histidine and
(P < 0.05) in raw than in cooked leg samples (Table arginine, were more concentrated in the cooked
4). samples. Lawrie21 has reviewed the effects of different
The proximate chemical composition of the lean heat treatments on the destruction and availability of
meat (of the various carcass components) from this the amino acids from the different traditional meat
394 J Sci Food Agric 80:390±396 (2000)Crocodile meat
types. The cooking temperature from this investiga- this meat is exported to Europe and the Far East. This
tion was not intense enough and was of too short a shift in production emphasis from skins to meat will
duration21 to in¯uence the amino acid availability. necessitate the evaluation of the in¯uences of size, feed
The mineral and fatty acid compositions of the lean composition and feeding regimes, growing facilities
meat from the crocodile tail samples are compared in and processing on the carcass yields of crocodiles.
Table 6 with those of beef and chicken. Similarly, studies on the chemical composition,
Of the minerals analysed, only iron differed sig- characteristics and uses of crocodile meat in processed
ni®cantly with treatment, the concentration being products are needed. Apart from providing baseline
higher in the cooked sample. The iron, magnesium nutritional values for crocodile meat, this investigation
and sodium contents of the crocodile meat were lower has shown that the meat from this species compares
than those of either beef or chicken. favourably with that of more traditional species such as
The major fatty acids present in the crocodile tail are beef and chicken. Crocodile meat could also be
oleic (C18:1o9) and palmitic (C16:0) acids, whilst marketed strategically as a healthy food owing to its
stearic (C18:0), linoleic (C18:2o6) and palmitoleic favourable unsaturated lipid fatty acid pro®le as well as
(C16:1o7) acids were also present in signi®cant its low sodium content.
concentrations. Mitchell et al 3 also found crocodile
meat (C porosus and C johnstoni) to contain high levels
of oleic (33.1%), palmitic (22.5%) and linoleic ACKNOWLEDGEMENTS
(15.2%) acids. These authors also noted high con- The authors are grateful to Mr K Prins of La Bonheur
centrations of the longer-chain polyunsaturated fatty Crocodile Farm, Paarl for providing the crocodiles and
acids, particularly arachidonic acid (3.6%). These assistance in conducting this study, and Mr AB Riffel
differences in lipid composition could be attributed to of Marine Oil Re®ners for help with the lipid fatty acid
both species differences and variations in diets. The analyses.
diets fed to the crocodiles in the investigation of
Mitchell et al 3 were not reported, whilst the crocodiles
in the present investigation received a commercial diet REFERENCES
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