EVALUATION OF THE QUALITY AND PROXIMATE COMPOSITION OF BEEF SOLD AT THE ABATTOIR OF KANO STATE, NIGERIA

This research was aimed at evaluating the pH of beef, as well as its cook loss value and water holding capacity, as well as its proximate composition of the beef from the Kano State abattoir. The proximate composition of the beef was also analyzed using standard procedures described by the Association of the Official Analytical Chemists (AOAC). The beef samples were aseptically obtained from the Kano state abattoir during the month of September when the animals were well fed and healthy, with five cows randomly selected and used for the analysis. The results indicate the pH for the beef to be 5.9, while the cook loss and water-holding capacity were found to be 32.71% and 24.33% respectively. The proximate contents were also reported as follows; protein content (21.50%); fat content (6.75%); ash content (0.92%) and moisture content (68.19%). The results in indicate that all the parameters analyzed for the beef obtained from the Kano abattoir are comparable with the results reported by various researchers, and are all within the standard acceptable limits. Consequently, this impart positive economic implications to the both seller and the consumer, as well as enhancing the meats taste and palatability. The present study concluded that the meat from the Kano State abattoir can be safely consumed by the consumers.


INTRODUCTION
Meat is the animal flesh that is eaten by man as food (Lawrie and Ledward 2006). The use of meat as food has been in existence since prehistoric times (Leroy and Praet 2015;Klaudia and Wojciech 2018). Meat belongs to one of the six major classes of food that provides the body with high quality essential proteins, minerals, vitamins and nutrients (Oh et al., 2016), as well as minerals and vitamins in order for the body to remain strong and healthy (Tsegay et al., 2015). Meat can be processed or manufactured products prepared from animal tissues, as well as all other animal tissues that are suitable for human consumption (Soniran and Okunbanjo 2002;Ameha 2006). Meat obtained from cattle is usually referred to as beef (Piatti-Farnell 2013).
The most important and most valuable components of meat are water, proteins, fats and minerals (FAO 2004;Ahmed et al., 2010;Tsegay et al., 2015), with the minerals and other chemical compositions of cooked meat drastically different from that of raw meat (Sainsbury et al., 2009;Tsegay et al., 2015). The effect of cooking on meat has also been studied, and it is reported that cooking increases the palatability, consumer preference, tenderness and the nutritive value of the meat (Pietrasik et al., 1995;Tornberg 2005;Tsegay et al., 2015). However, during cooking certain components of the meat are likely to be lost, with the lower the loss, the better the palatability of the meat (Ameha 2006;Tsegay et al., 2015). Such components likely to be lost include the water content.
The quality of beef is usually evaluated by the consumers on the basis of its tenderness, palatability, colour, juiciness, flavour content, neatness, etc. (Beriain et al., 2001), but scientifically, and probably the best way to evaluate and determine the quality of beef is to measure its water holding capacity, cooking loss, its pH, and its chemical composition (Abd El-Aal and Suliman 2007; Fakolade and Omojola 2008;Gustavson et al., 2011;Tsegay et al., 2015).
Deficiency of protein in most African countries is mainly the cause on malnutrition in both adult and children (Omoregie, 2001;Amaefule et al., 2006;Adejinmi et al., 2007) and this can be reduced to minimum with the availability of good quality meat (Adeniyi et al., 2011), since more than half of the World's cattles, buffaloes and sheeps are found in African countries (FAOSTAT 2000;Adeniyi et al., 2011).
An important quality of beef is its pH, which may vary between different cattle as a result of age of the animal, nutritional deficiencies, physical exercise and sex (Simela, 2004;Zhang et al., 2010;Gebrehiwot et al., 2018). When beef is cooked there is always reduction in its weight, and this is referred to as cooking loss. Cooking loss has both negative and positive effects to the consumer and the meat industry, because the meat products tend to loss a large amount of proteins and several essential minerals, and this causes drop in its nutritional quality, and subsequently lowers its purchasing value (Pearson and Gillett 1988). Another important factor that affects the quality of beef is the drip loss, or simply called the waterholding capacity. The quality of the beef and its yield are drastically reduced by low water-holding capacity. Low water-holding capacity also decreases the beef's juiciness and tenderness, and this reduces its demand by the consumers. However, beef's proximate composition is by far the most important quality (Pethick et al., 2011).
The main objective of this study is to determine and document on the quality and proximate composition of the beef meat sold at the abattoir of Kano state, Nigeria.

MATERIALS AND METHODS Sampling
Sampling was done in the month of September when the animals were well fed and healthy. The sampling was spread across the month, with the first sampling done in the first ten days of the month (Sample A), while the second one conducted in the second ten days of the month (Sample B), and the third and the last sampling was done in the last ten days of the month (Sample C). And during each sampling five cows were randomly selected and used. Fresh skeletal muscles from the cows were obtained from the Kano State abattoir in the early hours of morning when mass slaughters were done. Five slices (of reasonable and near same sizes) of the beef were made and then immediately put into a clean and dry jar for transportation to the laboratory for further analysis. Each procedure was repeated in triplicates and their averages reported.

Determination of the pH Value of the Beef
To obtain the pH of the beef, the method reported by Tsegay et al., (2015) was adopted. Here 0.5 g of the sample was ground in a blender and then diluted with 5 ml of distilled water, and the pH value was measured using the pH meter. This procedure was done in triplicate and during each measurement, the pH meter was recalibrated and the blender and all the apparatus used were washed with distilled water.

Determination of Cooking Loss of the Beef
The cooking loss of the beef was analyzed using the procedure described by Bouton et al., (1971) with slight modification as reported by Tsegay et al., (2015). Three fresh slices of the beef of 0.5 g weight were separately placed into three different test tubes, and were then placed in a boiling water bath for 5 minutes and then removed and cooled. The cook loss of the beef was obtained by taking the difference of initial and final weight. That is: where: W1 = Initial weight of the sample W2 = Final weight of the sample.

Determination of Water Holding Capacity of the Beef
The water holding capacity of the beef was determined using the method suggested by Kauffman et al., (1986) and Trout (1998), as modified and reported by Tsegay et al., (2015). Here 0.5 gram of the sample was placed between two filter papers, and this in turn was placed between two glass sheets weighing 4.64 g, and over all these a 50 g weight was placed. This gave a total compression weight of 54.64 g on the beef. The set-up was allowed to stand for 24 hrs. The water from the meat was found to be compressed and squeezed out and then absorbed into the filter paper. The filter paper was then dried, and the area of the filter paper for the shape of the meat and that of the absorbed water were measured using a plastic ruler. The water holding capacity was obtained by taking the difference between areas of absorbed water borderline on the filter paper (moisture) and the area covered by the meat.

Proximate Composition of the Beef
Determination of total protein, fat ash and moisture were performed according to the methods described by the AOAC (1990).

Determination of Meat Protein
The protein content of the beef was determined according to the method suggested by AOAC (1990) using the Kjeldhal method. Here 0.5 grams of the beef sample was put into a digestion tube and 5 ml of concentrated sulphuric acid (H2SO4) was added. Analyses were all carried out in triplicates and two blank samples without the beef sample were also taken. The digestion tube with its content was then placed in boiling water for 40 minutes and then the catalysts, CuSO4 and K2SO4, were added in the ratio of 7:1, and 10 ml of concentrated, H2SO4 was added, and then transferred to the digestion block. The sample was then digested at 300 O C for 3 hrs, until when the sample turned colorless. The sample was removed from the digestion block and then allowed to cool overnight. The aliquot was then diluted with distilled water to make up the volume to 250 ml. The sample was then made alkaline by adding 10 ml of 35% NaOH, and then distilled, with the distillate collected in a flask containing 4% boric acid (H3BO3), with bromocresol green taken as the indicator. The distillate was then collected for 5 minutes considering that all the ammonia was collected in the boric acid solution, and then titrated with 0.1 N H2SO4. The nitrogen obtained in the sample was then multiplied with 6.38 to determine the percentage protein of the beef.

Determination of Beef Fat
The beef fat was estimated using soxhlet extraction method as suggested by AOAC (1990). Three samples of 0.5 grams each of the dried beef samples were placed on a separate filter paper 74 and each properly tied with a string and then placed into a fat free thimble, and petroleum ether was used for the distillation. The samples were severally refluxed in the soxhlet apparatus to ensure complete removal of the fat. The sample was then taken out of the soxhlet apparatus and then it was transferred to a rotary evaporator to remove the solvent (petroleum ether). The sample was then reweighed after overnight cooling and the difference between the original and final weight was calculated using the formula below.

Determination of Ash Content of the Beef
The ash content of the beef was determined using the dry ashing technique as reported by Tsegay et al., (2015). Here three slices (0.5 g each) of the fresh beef were taken into different silica crucibles, and were then transferred into a muffle furnace. The furnace was then operated at a temperature of 600 O C and maintained for 6 hours. The samples (in the crucibles) were then allowed to cool overnight. The cooled crucibles (with their contents) were then transferred to a desiccator and then weighed. Each sample was weighed and reweighed three times and then the average weight was taken. Finally, the ash content was calculated using the formula below:

Determination of the Moisture Content of the Beef
To determine the moisture content of the meat the technique reported by Tsegay et al., (2015) was adopted and modified. Here the 0.5 g of the fresh beef was placed on a flat bottom aluminum dish, which was then heated at 105 O C overnight in hot oven. The sample was placed in a desiccator and then allowed to cool. The dried and cooled sample was then reweighed. The weight was taken three times and average weight calculated. The moisture content was measured as a difference between the initial and final weight of the sample.

RESULTS AND DISCUSSION Results
The results for the pH value of the beef obtained from the Kano abattoir, along with its cooking loss and water holding capacity, as well as its protein, fat, ash and moisture contents are all presented in Table 1 below.

DISCUSSION
The pH value (5.9) obtained for the beef obtained was found to be similar to that (5.6) reported by Tsegay et al., (2015), but was lower than the values reported by Fakolade and Omojola (2008) and Maiti and Ahlawat (2011). Low pH values may be attributed to the high lactic acid content in the muscles, and this can be due to several factors ranging from the distance travelled by the animal before slaughter, to the pre-slaughter handling, inadequate resting facilities between the travel and slaughter, (Yacob 2002;Ameha 2006;Elias et al., 2007), as well as the animals sex, with lactating mothers having low pH values because of constant conversion of glycogen to lactic acid (FAO 2004). Cooking loss of beef is the loss during cooking, and it measures the decrease in edible meat weight for human consumption (Gustavson et al., 2011). The mean value for the cook loss of the beef sample reported in this research work (32.71) was found to be similar to that reported by Tsegay et al., (2015) who reported 33.8% cook loss for beef from Hawassa city in Southern Ethiopia. The values are however higher than those reported by Jama et al., (2008) for Nguni, Bonsmara and Angus cattle breeds. The difference may be due to the breed of the animal, age and sex (Ameha 2007).
The water holding capacity of the beef sample reported in this study (24.33%) was found to be lower than those reported by Abd El-Aal and Suliman (2007), but higher than that reported by Adam et al., (2010). The values are however comparable to that reported by Maiti and Ahlawat (2011) and Tsegay et al., (2015). Low water-holding capacity makes the appearance of the meat unattractive, and consequently less attractive or appealing to the consumer, and this leads to low sells and turnover (Jama et al., 2008). Consequently, low water-holding The proximate composition of the beef obtained from the Kano abattoir was found to be similar to several reports by some researchers. The mean protein content for beef reported in this study (21.50%) was comparable to those observed and reported by Fernanda et al., (2003), Williams (2007), Fakolade and Omojola (2008) and Nikmaram et al., (2011). Arse et al., (2013) also reported a mean value of 23.2% for the beef of Arsi cattle in Adama town, Oromia, Ethiopia, and their result supports the observed result reported by the present research work. On another hand, the mean fat content (6.75%) reported for the beef from Kano abattoir was found to be similar to those reported by other researchers (Fernanda et al., (2003), Williams (2007), Fakolade and Omojola (2008) and Nikmaram et al., (2011) who reported similar results. With Arse et al., (2013) also reporting a mean value of 6.86% fat for the beef of Arsi cattle in Adama town, Oromia, Ethiopia, and their result supports the observed result reported by the present research work. The result for the ash content in beef in this research work (0.92%) was found to be similar to the results reported by Fernanda et al., (2003), Fakolade and Omojola (2008) and Nikmaram et al., (2011), with result (0.99%) reported by Arse et al., (2013) for the beef of Arsi cattle in Adama town, Oromia, Ethiopia, supporting the result reported by the present research work.
The result of the moisture content in beef obtained from Kano abattoir was found to be 68.19% and this agrees with similar result of 69.82% reported by Arse et al., (2013) for the beef of Arsi cattle in Adama town, Oromia, Ethiopia, and their result supports the observed result reported by the present research work. The result is also similar to that reported by Fernanda et al., (2003), Williams (2007), Fakolade and Omojola (2008) and Nikmaram et al., (2011). Note that, the moisture content of the meat is the amount of water held within the structures of its muscles, while the water holding capacity of the meat is the ability of the meat to retain that water (or moisture) when external force is exerted on it (Gebrehiwot et al., 2018). External forces like excessive heat, long distance walk, and poor storage of meat, thirst and starvation, as well as meat processing techniques may have negative effect on the water holding capacity of the meat (Gebrehiwot et al., 2018).

CONCLUSION
In this research work, the beef sold at the Kano State abattoir was collected and its quality and proximate compositions were analyzed using various techniques. The results obtained indicate that the pH value, cook loss, water-holding capacity, the protein, fat, ash and moisture contents of the beef obtained from the Kano abattoir are comparable with the results reported by various researchers. All the values were found to be within the standard acceptable ranges, and hence the meat from the Kano State abattoir can be safely consumed by consumers.