QUALITY PARAMETERS AND NUTRITIVE VALUE OF WILD AND CULTURED NILE TILAPIA SOLD IN ASSIUT CITY, EGYPT

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QUALITY PARAMETERS AND NUTRITIVE VALUE OF WILD AND CULTURED NILE TILAPIA SOLD IN ASSIUT CITY, EGYPT

SHERIEF M.S. ABD-ALLAH and HESHAM A.A. ISMAIL

Department of Food Hygiene (Meat Hygiene), Faculty of Veterinary Medicine, Assiut University, Egypt

Received: 26 September 2016;    Accepted:      October 2016

INTRODUCTION

Fish is a good source of the vitamins which required by human being, contains a good selection of minerals, and its protein compares favorably with that provided by meat, milk and eggs (FAO, 2001).

Commercial fresh-water fish culture started in Egypt in 1961, with a small contribution to fish production. In recent years, it contributes a large proportion (about 65%) of the total production which increased from 45000 ton per year in the mid 1980 to 705490 ton per year in 2009 to compensate the shortage in red meat production (GAFRD, 2010). Some Egyptian people use fish as the only source of animal protein throughout the year.

Nile tilapia is a fresh-water fish species, has been known as one of the most widely cultured species due to its fast growth rate and easy cultivation. It can tolerate a wide range of environmental conditions, able to reproduce in captivity, feed on low trophic levels and has good sensorial flesh properties (Boari et al., 2008 and Dergal et al., 2013).

Corresponding author: Dr. HESHAM A.A. ISMAIL

E-mail address: Sherief74@yahoo.com

Present address: Department of Food Hygiene (Meat Hygiene), Faculty of Veterinary Medicine, Assiut University, Egypt.

Fish ‘‘quality’’ has been assessed using various parameters including: texture, color, fat content, fatty and amino acids composition, mineral content, microbiological count and others (Haard, 1992; Rasmussen, 2001 and Jankowska et al., 2003). 

In sensory analysis; appearance, odor, flavor and texture are evaluated using the human senses. Flavor and other quality aspects of cultured fish may reduce consumer appeal when the cultured varieties are compared to their wild counterparts; farmed fish are known to express off-flavors (FAO, 1995 and Gonzalez et al., 2006).

The ultimate pH of fish flesh after death is related to the amount of available glycogen. The more glycogen present, the lower the pH of the fish flesh which improves the keeping quality (Hall, 1992).The pH determinations have been applied to assess the degree of quality deterioration as pH increases due to the production of ammonia and amines by microbial and tissue enzymes activity during storage (National Academy of Sciences, 1985).

Total volatile basic amines (TVB) include the measurement of trimethylamine, dimethylamine, ammonia and other volatile basic nitrogenous compounds associated with seafood spoilage. It is one of the most widely used measurements of seafood quality, where its significant increase indicates fish deterioration (FAO, 1995; Yao et al., 2009 and Noseda et al., 2010).

Fish lipids have high content of polyunsaturated fatty acids (PUFA), being very susceptible to oxidation. Some of the secondary oxidation products, aldehydes, have very unpleasant odors and flavors, responsible for the fishy and rancid character associated with spoiled fish. Thiobarbituric acid-reactive substances (TBA-RS), an aldehydic secondary oxidation products (FAO, 1995 and Ozogul et al., 2011)were reported to show some correlation between its level and fish quality (Hoyland and Taylor, 1991; Raharjo and Sofos, 1993; Yarnpakdee et al., 2012).

The fish flesh which is generally sterile immediately after catching, may get contaminated with different micro-organisms during subsequent handling, as these can penetrate from skin and gut to the flesh (Brock et al., 1984 and Etzel et al., 1998).Fish may be subjected to microbial contamination either during their presence in aquatic environment or after being harvested for marketing, where environmental conditions usually affect the growth and multiplication of such micro-organisms(FAO, 2012 and Amer et al., 2012).The presence of coliforms indicates a potable fecal source of contamination, and their presence in great number may raise the public health hazard (National Academy of Sciences, 1985).As well, Clostridium perfringens spores can reach fish in their water habitat (particularly near sewage outfalls) or during handling. Numbers greater than 10⁶ are necessary to cause illness. Such quantities do not reach foods by mere contamination, but accumulate as a result of multiplication of vegetative cells (Bryan, 1980).

Wild and cultured fish differed in nutrients (Nettleton and Exler, 1992), sensorial, chemical and physical properties (Cox and Karahadian, 1998; Grigorakis et al., 2003; Delwiche and Liggett, 2004). Diet availability is one of the major factors affected fish body composition (Lie, 2001; Alasalvar et al., 2002; Ashraf et al., 2011).  In wild fish, the composition was strongly influenced by the environmental conditions which determined the nutrients availability (Izquierdo et al., 2003), while in cultured fish, the feeding with artificial diets supplemented a wide range of nutrients and determined the flesh composition (Periago et al., 2005). The study of chemical composition of fish is of interest for the processor, nutritionist, cook and consumer as it influences both keeping quality and technological characteristics of the fish (Huss, 1988; FAO, 2001).

The increased production of cultured Nile tilapia has raised concerns over its quality in comparison with wild one. As consumers now are more aware of possible food hazards and have more demand in respect of freshness, naturalness, and microbial safety, so there is a need to access the quality, safety and nutritional value of fish and in particular cultured one.

For that, the main objective of this study was to shed light on the freshness, chemical and bacterial quality and proximate compositions of cultured and wild Nile tilapiafish, in order to provide information that guide consumers during selection between them under native conditions of Assiut city, Egypt.

MATERIALS AND METHODS

A total of 99 (50 wild and 49 cultured) samples of fresh Nile tilapiafish were randomly collected from different fish-sale markets in Assiut city, Egypt. The samples transported directly to the laboratory, being kept at 4ºC till being examined with a minimum of delay. At the laboratory, each sample was examined sensorily then was prepared for bacteriological and chemical examinations.

For bacteriological examination, the scales were removed by sterile instruments and the flesh with the skin intact collected in a sterile mortar. For chemical analysis, flesh without skin was collected in a clean mortar. Each part of the sample was then mixed thoroughly being ready for examinations. Prepared samples not subjected to direct analysis were kept at -20ºC till being analyzed.

1)       Sensory evaluation

The appearance of the skin, eyes, gills, flesh (cut from abdomen), color (along vertebral column), and organs; condition of the flesh, vertebral column, and peritoneum; as well as smell of gills, skin and abdominal cavity were evaluated by members of The Food Hygiene Department (Meat Hygiene) according to FAO (1995).  Ten characteristics were scored on a scale from 3 to 0. A mean score was obtained by dividing the scores summation by the number of the evaluated characteristics. Scores of greater than 2.7 are graded "E", from 2.0 - 2.7 graded "A", from 1.0 – 2.0 graded "B", and less than 1.0 graded "C" (un-official score; fish discarded for human consumption) (Hall, 1992).

2)       Chemical analysis

2.1. Chemical quality parameters

a) Determination of pH

The pH of the fish flesh was determined according to Lyhs et al. (1998) using pH-Meter (lovibond, SD50).

b) Determination of total volatile bases (TVB)

The TVB was determined according to Pearson (1976) using macro-kjeldahl apparatus.

TVB "mg N/100g fish flesh" = (Titration – Blank) x 14

c) Determination of thiobarbituric acid (TBA) (mg malonaldehyde/kg flesh)

Oxidative rancidity of the fish was determined by measuring the thiobarbituric acid-reactive substances (TBA-RS) according to Buege and Aust (1978).  

2.2 Chemical composition

The determination of moisture, fat, crude protein, and ash contents of the samples, as well as calculation of the total carbohydrate was done according to AOAC (2000).

a) Determination of moisture content

The free water content of the flesh was determined using hot air oven (Fine Tech, Korea)

Moisture % =    Weight lost    x 100

                      Sample weight

b) Determination of fat content

Fat percentage of the sample was determined using ether extract (Soxhlet) method with a slight modification. Briefly, 1 gm (dry weight) of each sample was weighted onto filter paper of known weight, wrapped and extracted with petroleum ether (60/80) in the Soxhlet apparatus for 16-18 hrs. The extracted samples was then dried overnight in hot air oven at 65°C, transferred to desiccator and left to cool, then weighted. The loss in weight was used to calculate the fat percentage.

Fat % =    Weight lost    x 100

                Sample weight

c) Determination of crude protein content

Macro-Kjeldahl method was used to determine the total nitrogen percentage of the sample. From the dried sample 0.5 gm was used for digestion.

Crude protein % = Total nitrogen x 6.25

d) Determination of ash content

  One gram (dry weight) of the sample was ashed using the muffle furnace (Thermolyne, USA).

Ash % =    Weight of the ash    x 100

                      Sample weight

N.B.: All estimations on the dry weight were converted to the wet weight basis using the following equation according to Jurgens and Bregendahl (2007) before being used in the subsequent calculations.

Nutrient wet basis % =    Nutrient dry basis % x Dry matter %

                                                              100

e) Calculation of the total carbohydrate content

The carbohydrate percentage was calculated by subtraction using the wet weight basis of the content.

Total carbohydrate % = 100 – (moisture % + protein % + fat % + ash %).

f) Calculation of the gross energy value

According to Merrill and Watt (1973) the gross energy value per 100 gm of fish flesh was calculated using the following equation:

Gross energy value (Kcal/100g) = (protein % x 4) + (fat % x 9) + (carbohydrate % x 4).

3)     Bacteriological estimation

3.1. Preparation of samples

Under aseptic conditions, 10 grams of each sample were removed and transferred into sterile plastic bag, and then 90 ml of 0.1% sterile peptone water was added. The contents were homogenized for 2 min in the stomacher (Seward 400). Ten fold serial dilutions were prepared using sterile 0.1% peptone water.

N.B.: Three tubes dilutions method was used to calculate coliforms, fecal coliforms and E. coli most probable number (MPN) count according to AOAC (1980)

3.2. Coliforms count (MPN/g)

Laury sulphate broth (Oxoid, CM0451) was used as inoculation medium for presumptive enumeration of coliforms, while brilliant green bile (2%) broth (Himedia, M121) was used for confirmatory enumeration

3.3. Fecal coliforms count (MPN/g)

EC medium (Lab Media, LAB171) was used for the count being incubated in water bath at 45±0.5°C.

3.4. E. coli count (MPN/g)

Eosin methylene blue "EMB" agar (Oxoid, CM69) was used for inoculation. Typical colonies are nucleated (dark center) with metallic sheen.

3.5. Enumeration of Clostridium perfringens (MPN/g)

Lactose sulfite broth (Biolife, ref 4015792) was used for inoculation according to Beerens et al. (1980), being incubated at 46±0.5°C.

RESULTS

Sensory evaluation of the wild tilapia samples revealed that 41 (82%) and 9 (18%) of them were of grades "A" and "B", respectively. For cultured tilapia, 30 (61.22%) samples were of grade "E" while, 19 (38.78%) were of grade "A" as shown in Table 1. The minimum, maximum and mean values for wild tilapia sensory evaluation were 1.59, 2.5, 2.17±0.03, respectively, while for cultured tilapia were 2.1, 2.8, and 2.72±0.02, respectively. The sensory score mean value for the cultured tilapia was significantly (P<0.05) higher than in the wild (Table 2, 4, 6 and Figure 1).

Concerning chemical quality parameters, the minimum, maximum and mean values for pH, TVBN and TBA in wild tilapia were 6.41, 7.52 and 6.81±0.03; 11.2, 25.2 and 17.81±0.5 mg N/100g fish flesh; and 0.19, 5.43 and 1.84±0.17ppm, respectively (Table 2). In case of cultured tilapia the previously mentioned values were 6.41, 7.08 and 6.79±0.02; 14, 28, 21.38±0.63 mg N/100g flesh; and 0.04, 3.1 and 1.02±0.08 ppm, respectively (Table, 4). There was no significant difference between wild and cultured tilapia for mean value of pH. For TVBN mean value, it was significantly (P<0.05) higher in cultured tilapia, while for TBA mean value, it was significantly (p<0.05) higher in wild than in cultured tilapia (Table 6 and Figure 1).

Regarding bacterial quality parameters, the data recorded in Table 3 show that 44 (88%) and 17 (34%) of the 50 examined wild tilapia samples were positive for coliforms and fecal coliforms count, respectively. However, none of the examined samples was positive for the E. coli or Cl. perfringenes count. The minimum, maximum and median values for coliforms were 3.6, 1100 and 9.1 MPN/g, respectively, while for fecal coliforms were 3, 150 and 9.1 MPN/g, respectively. In case of cultured tilapia, 41 (83.67%), 20 (40.82%) and 3 (6.12%) out of the 49 examined samples were positive for coliforms, fecal coliforms and Cl. perfringenes count, respectively. The minimum, maximum and median values for the previously mentioned bacteria were 2.3, >1100 and 26; 3, 1100 and 9.1; and 7.3, 43 and 9.1 MPN/g, respectively. Only one sample was positive for E. coli with a count of 3.6 MPN/g (Table, 5).

The results of chemical composition analysis revealed that the moisturepercentage in wild tilapia ranged from 77.86 to 82.15 % with a mean value of 79.63±0.13. For protein, fat and ash the values ranged from 14.78 to 19.41, 0.41 to 2.16, and from 0.85 to 1.22% with mean values of 17.5±0.12, 1.2±0.05, and 1.04±0.01, respectively. Calculated carbohydrate percentage ranged from 0.04 to 1.26, with a mean of 0.63±0.06 (Table, 7). With respect to cultured tilapia, the data registered in Table 8 declare that the moisture, protein, fat and ash percentages ranged from 73.74 to 80.38, 15.27 to 19.63, 1.2 to 4.9, and from 0.89 to 1.45 % with mean values of 77.17±0.22, 17.91±0.15, 2.82±0.13, and 1.17±0.02, respectively. The calculated carbohydrate showed a minimum of 0.1%, a maximum of 1.94% and a mean value of 0.94±0.07. The mean value for moisture was significantly (P<0.05) higher in wild tilapia; while those of protein, fat, ash and calculated carbohydrate were significantly (P<0.05) higher in cultured tilapia (Table 9).

As recorded in Table 10  the calculated gross energy values (Kcal/100g fish flesh) ranged from 73.75 to 92.51 in wild tilapia with a mean value of  83.29±0.06 and from 85.2 to 124.77 in cultured tilapia with a mean value of 100.73±1.44, which is significantly (P<0.05) higher than in wild tilapia.

Table 1: Sensory grading of wild and cultured Nile Tilapia

Grade E: > 2.7; Grade A: 2-2.7; Grade B: 1-2; Grade C: <1

Table 2: Sensory and chemical quality parameters of wild Nile Tilapia(n= 50)

*n= 41; the other 9 samples size was not enough for the TVN determination

Table 3: Bacterial quality parameters of wild Nile Tilapia(n= 50)

*The confirmatory count

Table 4: Sensory and chemical quality parameters of cultured Nile Tilapia(n= 49)

*n= 41; the other 8 samples size was not enough for the TVN determination

Table 5: Bacterial quality parameters of cultured Nile Tilapia(n= 49)

*The confirmatory count

Table 6: Mean values of sensory and chemical quality parameters of wild and cultured Nile Tilapia

Means with different superscript in the same raw are significantly different (P<0.05)

Figure 1: Comparison between mean values of sensory and chemical quality parameters of wild and cultured Nile Tilapia

Table 7: Chemical composition (%) parameters of wild Nile Tilapia(n= 50)

Table 8: Chemical composition (%) parameters of cultured Nile Tilapia(n= 49)

Table 9: Mean values of chemical composition (%) parameters of wild and cultured Nile Tilapia

Means with different superscript in the same raw are significantly different (P<0.05)

Figure 2: Comparison between mean values of chemical composition (%) of wild and cultured Nile Tilapia

Table 10: Energy value (Kcal/100g flesh) of wild and cultured Nile Tilapia

Means with different superscript in the same column are significantly different (P<0.05)

DISCUSSION

The quality of any kind of fresh fish includes different parameters such as organoleptic examination, chemical parameters such as pH value, TVB and microbial load. The increased production of Nile tilapia has raised concerns over the quality of the cultured fish in comparison with the wild fish.

Results of sensory evaluation showed that all of the examined cultured and wild fish samples were organoleptically accepted. The mean value of sensory scores was significantly (P<0.05) higher in cultured tilapia (2.72±0.02) than in wild one (2.17±0.03). Most of the samples (61.22%) had a sensory grade "E" for cultured fish, while most of the wild fish samples (82%) had a grade "A". Cultured fish usually kept chilled in crushed ice directly after catching that help to keep their fresh state, and allow slow occurring and long lasting rigors, which may raise the fish sensory scores. The obtained results for wild tilapia are in line with those recorded by Ammar (2001) who stated that all the examined tilapia samples were organoleptically accepted with a mean score value of 2.1±0.09 and that most of the examined samples (68%) were of grade "A". Haard (1992) mentioned that wild fish were found to have better texture than cultured one of the same species, which in part disagreed with the present findings.

Knowledge about the pH of fish meat may give valuable information about its condition. The recorded pH values of cultured tilapia was lower than that of wild one, with no significant difference (P>0.05) between their mean values. This was partially agreed with those found by Baz et al. (2014) who recorded lower pH for cultured than for wild tilapia but with significant difference between them. The current pH mean value was higher than that recorded by the previous authors for cultured (5.84±0.02) and wild (5.92±0.23) tilapia. Likewise, Ammar (2001) and El Said et al. (2011) recorded lower pH mean value (6.64±0.06 and 6.4±0.4, respectively) for wild tilapia. The lower pH values in cultured tilapia may be attributed to the higher carbohydrate (glycogen) content of its flesh (0.94%) in comparison with that of wild tilapia flesh (0.63%).  The ultimate pH of fish flesh after death is related to amount of glycogen available at death. The more glycogen present, the lower the pH value (Hall, 1992).

Total volatile base (TVB) mean value (mg/100g flesh) was higher, while thiobarbituric acid (TBA) mean value (mg/kg) was lower in cultured than in wild tilapia with a significant difference (P<0.05) between them. This disagreed with the findings of Baz et al. (2014) who reported lower TVB and higher TBA mean values in cultured than in wild tilapia, with a significant difference only in case of TVB. In general, the authors reported mean values for TVB (7.92±0.49 and 10.39±0.05) and for TBA (0.26±0.01 and 0.22±0.02) in cultured and wild tilapia, respectively, which is lower than the present results. As well lower TVB mean values, 11.71±1.2 and 12.32±1.6, were recorded for wild tilapia by Ammar (2001) and El Said et al. (2011),respectively.  In the same line,Hassan (2011) noted lower TVB (12.3±0.4) and TBA (0.29±0.04) values for fresh fish samples.

According to the Egyptian standards for chilled fish, the TVB value must not exceed 30 mg/100g flesh and TBA value must not exceed 4.5 mg malonaldehyde/kg fish flesh (EOSQC, 2005). It is clear from the obtained results that all the examined cultured and wild samples were not exceeding the previous limits except for only 2 (4%) samples of wild tilapia which had TBA values above 4.5 mg (4.87 and 5.43 mg), despite they are still organoleptically accepted (both have score "B"). These results partially in comply with those recorded by Baz et al. (2014) for cultured and wild tilapia and by Ammar (2001) and El Said et al. (2011) for wild tilapia samples.

The results of bacterial quality parameters revealed that the values of coliform, fecal coliform, E. coli, and Clostridium perfringens count (MPN/g) were higher in cultured than in wild tilapia samples. In cultured fish 83.67, 40.82, 2.02 and 6.12% of the examined samples were contaminated with the previously mentioned microorganisms, respectively. Meanwhile, in wild fish 88 and 34% of the examined samples were contaminated with coliform and fecal coliform, respectively, and none of the samples were contaminated by E. coli or Clostridium perfringens. 

Of the positive (41) cultured fish samples, 7 (17.07%) were have coliform count of 1100 and only 1 (2.44%) was have a count >1100 MPN/g. For wild fish, only 1 (2.27%) sample of the positives (44) was have a count of 1100 and none found to have count >1100 MPN/g. For fecal coliform, only 1 (5%) of the positive (20) cultured fish sample show a count of 1100, while none of the wild samples show such count. Clostridium perfringens and E.coli were recorded at low counts in the cultured tilapia samples only.

El Said et al. (2011) recorded coliform count ranged from 0.5x10³ to 3.5x10³ with a mean value of 1.69x10³±0.15x10³ cfu/g in all the examined wild tilapia samples, which was higher than the current findings. As well, Ammar (2001) detected higher incidence (80%) of anaerobes and a count ranged from 1x10 to 1x10⁵ with a mean value of 4.5x10³±3.9x10³ cfu/g in the wild tilapia samples.

The Egyptian standards (EOSQC, 2005) for chilled fish stated that coliforms count must not exceed 100cfu/g.  Regarding that, 26.53 and 10% of the examined cultured and wild tilapia samples, respectively, were found exceeded this limit. This result was lower than that recorded by El Said et al. (2011) for wild tilapia, who found coliforms in all the examined samples.

High incidence of coliforms (83.67%), fecal coliforms (40.82%) and the presence of E. coli and Clostridium perfringens in some of the cultured fish samples can suggest fecal contamination either from the rearing environment (use of drain water or organic matter of human origin for fish rearing)  or during handling which may suppose public health hazard. Gram and Huss (2000) stated that the high coliforms count in the examined samples was indicative of massive contamination with deteriorative bacteria which mostly lead to flavor deterioration of the fish. On the other hand, the low coliform count in wild sample may be suspected because of their free living and natural feeding, despite may indicate poor hygiene.

For proximate chemical composition, the data presented in Table (9) and Figure (2) revealed that cultured tilapia showed significantly (P<0.05) lower moisture, but higher protein, fat, ash and carbohydrate contents in comparison with their wild counterparts. Baz et al. (2014)declared that the mean value of moisture, fat and ash percentages of the cultured tilapia fish had a higher level than that of wild fish, while protein percentage is lower, which was in partial agreement with the present findings. The authors attributed that to feeding of cultured fish on a ration contain a high level of fat and ash, beside the long period of culturing till marketing.

Sulieman and James (2011) recorded non-significant difference (P>0.05) for moisture and ash content between wild and cultured tilapia, while protein and fat contents were significantly (P<0.05) higher in wild fish than in cultured one, which in contrary with the present observations. Likewise,Muchiri and Nanua (2006)reported that nutritional composition of cultured Nile tilapia was not significantly vary from the wild catch fish except for the lipid content.

FAO (2001) reported that total ash rarely exceeds 1-2 per cent of the edible portion of fish, which is in line with the current findings. Nearly similar moisture (79.43%), lower lipid (0.42%) and protein (15.77%) and slightly higher ash (1.42%) were detected for wild tilapia flesh by de Silva and Rangoda (1979). On the other hand Wimalasena and Jayasuriya (1996) observed lower moisture (78.3±1.3), higher lipid (2.3±0.7), and nearly similar protein (17.8±0.7) and ash (1.1±0.1) contents for wild tilapia flesh.

Mohammed (2013) reported nearly similar moisture and fat contents for wild tilapia (79.27±0.22 and 1.17±0.34, respectively), but lower protein (16.74±0.3) and higher ash (1.45±0.45). On the other hand, lower moisture, higher protein and fat and nearly similar ash values were recorded for wild tilapia by Adam et al. (2015).

Celik (2008); Grigorakis et al. (2002) and Gonzalez et al. (2006) found in other fish species that the wild fish were have a higher protein content than their cultured counterparts attributing this to their significantly lower moisture content which is in opposite with the current findings. Yeganeh et al. (2012) and Periago et al. (2005) stated that muscle fat levels of the cultured and wild fish showed no significant differences (P > 0.05), a matter which disagreed with the present results. On the contrary, Alasalvar et al. (2002); Olsson et al. (2003); Rodriguez et al. (2004); Gonzalez et al. (2006) and  Mnari et al. (2007) showed a higher muscle fat content in the cultured than in the wild counterparts which is in line with the present data.

Higher lipid content in cultured fish is expected when compared to their wild counterparts due to a variety of factors including availability and type of food, dietary ingredients (commercial diets are usually high in fat content and also include dietary carbohydrate), higher energy consumption in cultured fish when compared to wild fish, and possible periods of starvation encountered by wild fish (Haard, 1992; Grigorakis et al., 2002). It is worth to mention that Grigorakis et al. (2002) stated that fatty acid in the feed accumulated largely unchanged in the lipid of marine fish because of their reduced capacity for the chain elongation and desaturation.

The current results for carbohydrate either for cultured or wild tilapia were in line with that stated by FAO (2001) "the amount of carbohydrate in white muscle is generally too small usually less than 1 per cent". De Silva and Rangoda (1979) andMohammed (2013) recorded higher carbohydrate content for wild tilapia, while Henin (2016) recorded a higher content for cultured tilapia. On contrary, Wimalasena and Jayasuriya (1996) detected no carbohydrate in the flesh of wild tilapia.

The results of the gross energy content (Kcal/100g flesh) revealed significantly lower value for wild tilapia than for cultured one. This may be mainly attributed to the higher fat content of the cultured tilapia flesh. Mohammed (2013) reported nearly similar energy value (84.69±3.24) for wild tilapia, while Henin (2016) recorded lower value (91.41±1.43) for cultured tilapia.

From the previous data it could be concluded that, from the quality point of view wild Nile tilapia is better than the cultured one. Despite cultured fish seems higher in its nutritive value especially protein content; the high fat content of its flesh, which may be saturated (represents an area deserved of future research), could make it unsuitable diet for consumers especially those who are at risk of cardiovascular diseases. Moreover the high microbial load (coliforms and fecal coliforms) of cultured tilapia may signal public health hazard. As consumers expect cultured fish to be equivalent or superior to the wild one, therefore more control is required on different stages of the rearing, feeding and processing steps to deliver to consumers a designer tilapia fish with preferred quality and nutritional compositions.

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