Cooking loss measures the amount of shrinkage expected upon cooking of a particular meat sample. This, apart from affecting the yield also affects the nutritive value of meat. The low value is expected that most of the nutrients contained in such meat would have been leached into the broth resulting in poor quality of such cooked meat. The cooking loss (26.23%) of the raw beef obtained in this study was slightly higher than the cooking loss of 24% obtained by Okubanjo et al. (2003) for Bunaji breed of cattle and 22.50% reported by Jeremiah and Gibson (2003), but does not exceed 30% reported by Razminowicz et al. (2006) in pasture feed-steers.
The variability could be attributed to differences in the animals been evaluated in terms of marbling, breeds, etc (Nour et al., 1994; Yu et al., 2005).
The moisture, crude protein, ash and ether extract contents of the beef that were respectively 78.07%, 21.79%, 3.40% and 3.92% were slightly higher than 76.56%, 19.57%, 2.90%, and 1.50% obtained by Omojola et al. (2009) for beef used in the production of Kundi. The moisture and fat contents were higher than 73.10% and 2.80%, and the crude protein less than 23.20%
obtained for Australian beef as reported by Sinclair et al. (1999). However, the crude protein obtained was similar to 21.87% reported by Solomakos et al. (2008), while the ether extract (2.47%) and moisture (72.27%) contents obtained by these researchers were slightly less than the values obtained in this study. The difference in the meat chemical composition could arise as a result of either the difference in age and breed (Okubanjo et al., 2003), sex (Gašperlin et al., 2006) and nutrition of the animal from which the muscles were obtained. Generally, this corroborates the report of Okubanjo et al. (2003) that different breeds of cattle possess different meat characteristics.
The yields of meat floss from the different oil types were similar (68.55%, 69.11%, 69.38%).
The amounts of oil absorbed by meat floss during frying were also similar, which might have accounted for the similarities in their yield percentages.
Iodine value is measure the degree of unsaturation of oil. The higher the iodine number, the higher the degree of unsaturation which implies that such oil contains more of double bonds (polyunsaturated fatty acids). The iodine values obtained for the different oil used in this study indicate that palm oil had a lower degree of unsaturation compared to either groundnut oil or soya oil and this was reflected in their fatty acids proportion, that is, the typical composition of
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the oils (soya oil - 15% saturates, 85% unsaturates; groundnut oil - 22% saturates and 78%
unsaturates; palmoil 50% saturates and 50% unsaturates).
The difference in the nutrient composition of meat floss could be ascribed to the difference in the chemical composition of the oils used because a fried product will assume the nutrient composition of the frying medium (Fillion and Henry, 1998). The moisture content (11.38%-14.17%) obtained for meat floss in this study is lower than 33.40-39.81% contained in Kundi as reported by Omojola et al. (2009). The lower moisture content obtained could be attributed to the fact that production of meat floss is a dehydration process which means water and water soluble substances are extracted from the product during the deep frying and transferred to the cooking fat (Choe and Min, 1997).
The increase in the protein content of the products could be a result of reduction of its moisture content because water is a nutrient diluent. The less the water, the higher the protein content. The increase in protein content may also be due to the conformational changes of proteins, which might have occurred on heating. The heating brought about denaturation, followed by structural changes referred to as protein-protein interactions, which result in the aggregation of proteins (Tornberg, 2005). The increase in protein content observed for meat floss agrees with the report of Egbunike and Okubanjo (1999), that intermediate moisture meat are meats low in moisture content and contain three to four times the raw protein equivalent hence they are less bulky. The crude protein obtained in this study was lower than 69.80%-72.10% obtained by Soniran and Okubanjo (2002) for pork loin roast-cooked to an internal temperature of 65ºC - 85 ºC. The protein value (43.43%- 44.55%) obtained for meat floss in this study is also lower to the values of 52.29%, 58.89%, 53.42% obtained in kundi made from beef, camel and chevon respectively (Omojola et al., 2009).
The increase in ash contents could be attributed to the heat treatment which the products were subjected. Igene and Ekanem (1985) reported that ash content of meat increases during heat application. The ether extract contents of meat floss obtained in this study increased and was higher than 3.80-4.60% obtained by Omojola et al. (2009) for kundi. The deep frying stage in the production of meat floss might explain the increase in fat content of the product. Abiona et al. (2011) reported that during frying as water molecules are released, the product being fried absorbs the surrounding fat to compensate for the loss of water at the surface.
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In a retail environment, colour is a critical sensory characteristic of meat as it is experienced by consumers before tenderness or flavour and tends to be used as an indicator of perceived quality and freshness (Carpenters et al., 2001). Colour is one of the key quality attributes of meat and processed meat products (Cierach and Stasiewicz, 2007). Therefore, colour is probably the single greatest appearance factor that determines whether meat will be purchased (Florek et al., 2007).
The most important factors that determine the colour quality of processed meat products include recipe, contents of nutrients, pH, molecular pressure of oxygen, water activity, packaging method, storage temperature, air humidity, access of light and oxygen, type of package used, and permeability of gases (Cierach and Stasiewicz, 2007).
It would have been expected that meat floss from palm oil will have different colour compared to meat floss from other oils because of the presence of beta carotene, which accounts for the reddish colour of the oil. The colour of palm oil has been removed during bleaching of the oil before being used for meat floss production. Generally, the desirable colour of shredded meat is golden brown; and any difference in colour characteristic is contributed by the ingredients and frying temperature (Lin et al., 1999). The colours of meat floss from the three oils were acceptable to the panelists most probably because during preparation, similar ingredients were used and upon frying, care was taken to stop immediately the golden brown colouration was achieved.
The eating quality which is a combination of tenderness, flavour and juiciness is one of the most important characteristics by which consumers judge meat quality (Grunert et al., 2004), and one of the attributes that is most difficult to evaluate before purchase because it is not visible and highly variable (Verbeke et al., 2010).
Aroma and flavour are quite subjective characteristics of meat that are difficult to evaluate by the panelists compared to many other traits like texture, temperature and pH that are measurable in more exact way (Poławska et al., 2011). Aroma perception is usually mediated by the olfactory sense while flavour is perceived by the sense of taste and usually felt in the mouth. The aroma of meat floss from groundnut oil is more preferable to the panelist than those of meat floss from other oil types. This might be due to the distinctive appealing characteristic odour of groundnut oil that is easily perceived at a distance. The flavour of meat floss from soya oil was more preferable to the panelists, with the score rating above average (5.89) and higher than 4.67 and
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4.56 scores obtained for meat floss produced from groundnut and palm oils respectively. This might be attributed to the fact that it has high fat content because the flavour of a product is fat dependent. Also, its high flavour score may also be a result of its high protein content (44.55%) compared to 43.83% obtained for meat floss from groundnut oil.
Risvik (1994) described tenderness as one of the main meat quality attributes important for its acceptability and purchasing intention of consumers. Tenderness as a trait consists of such elements as ease of shearing or cutting during mastication (Cooper and Horbańczuk, 2002). It was expected that the beef meat floss from either groundnut or soya oil will be more tender because both oils contain appreciable amount of polyunsaturated fatty acids which ought to make the product to be soft compared to product from palm oil, but the reverse is the case because the panelists rated meat floss from palm oil as best in tenderness. However, the juiciness of both meat floss from groundnut oil and soya oil was rated high numerically by the panelists as the best. This may be accounted for by the presence of high level of polyunsaturated fatty acids in the two oils.
In overall acceptability, the meat floss from the three oils were scored above intermediate (6.33, 6.56, 6.11), and were rated almost the same in acceptability by the panelists.
It was expected that the freshly prepared products should not contain microbes, especially because of its exposure to high temperature during frying, but some microbes were recorded in the product when freshly prepared. These microbes are assumed to be thermophyllic which bypassed the high heat treatment that the products were subjected to during processing. Also, such microbes could arise because the environment is not void of microbes, which can get into product from the air during cooling or through the clothes worn during the processing of the product.
The high microbial load of meat floss produced using soya oil can be attributed to the presence of high nutrient profile of the product. The product from soya oil had high protein and ash contents and second in moisture and ether extract contents. This high nutrient content may indicate that the product from soya oil had abundant available nutrients for microbial growth.
The high microbial load of the products in polyamide may be attributed to the fact that the medium is prone to easy damage, which will make it permeable to oxygen, light and moisture.
These factors will aid the growth of aerobic microbes and make them to proliferate rapidly. Since
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the product may contain some anaerobic microbes, the proliferation of aerobic microbes in the medium will cause an increase in microbial load unlike polyethylene and acrylic bottle which are assumed to be air tight and are assumed to contain only anaerobic microorganisms.
The later decline in the microbial load during storage may be attributed to some of the spices used as flavouring agents (e.g. cloves and thyme) that contain phenolic compounds which have antimicrobial properties (Davidson and Naidu, 2000; Elgayyar et al., 2001; AbdEl-Hamied et al., 2009). It may be assumed that the phenolic compounds that were released during storage retarded growth and proliferation of the microbes. Generally, the reduced microbial load obtained in this study agrees with the report of Oke et al. (2009) that plant extracts and essential oils constitute a natural source of antimicrobial mixtures or pure compounds and these are used as natural agents to prevent the growth of food borne bacteria and moulds in food system as well as resulting in extension of the shelf life of processed foods.
The thiobarbituric acid reactive substances (TBARS) measurement is routinely used as an index of lipid oxidation in stored meat products. The result obtained in this study showed that the rate of lipid oxidation in the product was high in the meat floss produced using soya oil as it recorded the highest TBARS values. The low TBARS, hence low lipid oxidation rate in palm oil might be attributed to the fact that palm oil contains equal number of saturated and unsaturated fatty acids (50% saturated and 50% unsaturated fatty acids), unlike groundnut oil which contains 22%
saturated and 78% unsaturated fatty acids, and soya oil which contains 15% saturated and 85%
unsaturated fatty acids. Furthermore, the low TBARS in products from groundnut oil, despite its high unsaturated fatty acids may be due to the fact that the unsaturated fat is more of monounsaturated fatty acids. Groundnut oil contains 49% monounsaturated and 29%
polyunsaturated fat, unlike 23% monounsaturated and 62% polyunsaturated found in soya oil.
Also like groundnut oil, palm oil contains more monounsaturated fatty acids (40%
monounsaturated and 10% polyunsaturated).
Furthermore, the presence of high monounsaturated fatty acids implies that such oil will contain low sites for reaction with other compounds. That is, it has more of single double bond sites and will be less susceptible to lipid oxidation unlike when the oil contains more polyunsaturated fatty acids which indicate more of double bond sites for reaction to occur. Though the results of iodine values for groundnut oil and soya oil were not different, the two oils have a high degree of
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unsaturation compared to palm oil, which may indicate that they will be more susceptible to lipid oxidation than palm oil.
Furthermore, the susceptibility of soya oil to lipid oxidation could also be attributed to the fact that it contains a high proportion (7-10%) of oxidation-prone linoleic acid, a fatty acid which makes it less stable and sensitive to oxidation (USDA, 2004). This agrees with the report of Ghita et al. (2010) that polyenoic acids, such as linoleic acid, are much more sensitive to oxidation and the rate of peroxide formation is much rapid. The low susceptibility of palm oil to lipid oxidation could also be traced to its high content of vitamin E (tocopherol) which is a natural antioxidant (Zagre and Tarini, 2001). This might have accounted for the stability of palm oil (Sundram et al., 2002). This result also agrees with the report of Ghita et al. (2010) that different oils have different rate of lipid oxidation because of the difference in their degree of saturation and that oil high in linoleic acid are much more sensitive to lipid oxidation.
Generally, it was observed that the rate of lipid oxidation increases as the day of storage increases which corroborates the report of Singh et al. (2011) that TBARS increases as the number of days of storage increases. Nevertheless, in this study all results obtained at three weeks of storage of the products indicated that the products are still consumable because the TBARS value obtained does it exceed the threshold/critical value of 3 mg/kg at which rancidity is observed in stored meat products as reported by Wong et al.(1995). Also, the slow rate of the lipid oxidation could be attributed to some antioxidants, which may be present in some of the spices used (Wang et al., 1996). Esmat and Ferial (2010) reported slow rate of lipid oxidation during storage of meat steaks when various antioxidants were used.
The high TBARS value obtained for products in polyamide packaging medium might be due to entry of air, as the material may not be air tight as assumed for polyethylene and acrylic bottles.
Therefore, the product stored in polyamide is prone to damage because oxygen contained in the air received will aid the rate of lipid oxidation, thereby increasing the value of TBARS of the products. Oxygen is the most common and essential component for the progress of lipid oxidation (Ahn et al., 1992).
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CHAPTER SEVEN Summary and Conclusion