Studies On Optimization Of Enzymatic Dehairing Andeffect Of Dehairing Methods On Edible Quality

As one of main by-products during slaughtering and processing of beef, cowhide is mostly used as raw materials in leather industry. Influenced by factors such as small scale, heavy damage of cowhide, low market competition ability and transition of leather processing to the developing countries, increment of cowhide market is low with a poor expectation of future changes. There is a good prospection for pickled cowhide, which has been consumed by people in South-Eastern Asia and some minorities in South China. However, the generalization is difficult due to much remanent feather using traditional way of scalding and singeing and bad impression about safety. To solve the problems, the thesis systematically studied the influences on dehairing effects, safety, nutrtion by composition of dehairing bio-enzyme, processing temperature, time and so on, and sensory evaluation system for pickled cowhide, which hopefully can be a fundamental base for further researches on cowhide dehairing. The main results are as follows:(1) Optimizationof enzymatic dehairingTemperature, time, p H and concentration of enzyme were chosen as independent variations. Comprehensive grade of total protein concentration, total sugar concentration and collagen concentration of enzyme solution was as dependent variations. Optimizing researches were conducted using response surface methods. Results showed that the proper craft parameters for composite enzymatic dehairing were: first add of alkaline enzyme and second add of neutral enzyme with a ratio of 6:4; temperature was 45 ℃; time was 2.60 h for alkaline enzyme and 2.50 h for neutral enzyme; p H value was 10.5 for alkaline enzyme and 7.5 for neutral enzyme; concentration of enzyme was 1850 U﹒m L-1.(2) Evaluation of safety and nutritional quality of cowhide dehaired by enzymeThe influence on safety and nutritional quality of cowhide treated by scalding, singeing and enzyme was studied through determination the content of microorganism, heavy metal and nutrition based on national standards. Results suggested that heavy metals( As, Hg, Pb, Ge, Cr), Staphylococcus Aureus, Salmonella, Shigella And Escherichia Coli were not detected; the total aerobic plate count and coliforns were with a larger number dehaired by enzyme than by scalding and singeing; differences were obvious in the content of protein and water(P < 0.05) between two different methods; there were palmitic acid, stearic acid, palmitoleic acid, linoleic acid, myristic acid, nutmeg acid and arachidonic acid detected in cowhide dehaired by scalding and singeing, but only palmitic acid, stearic acid, palmitoleic acid and linoleic acid detected from cowhide dealt with enzymatic dehairing; a total of 17 kinds of amino acid was fund in both methods with no differences in the concentration(P > 0.05).(3) Constructing sensory evaluation of pickled cowhideThe descriptive words of pickled cowhide were collected and select descriptive words for pickled cowhide by M-value, principal component analysis and correlation analysis. Seven key indexes can basically cover the sensory features of pickled cowhide including pickled flavor, hardness, colour, fat content, elasticity, chewy and aftertaste. They included 4 aspects(outlook, quality, flavor and taste) and can evaluate the edible quality of pickled cowhide.(4) Effects of enzymatic dehairing on edible quality of pickled cowhideEvaluation of edible quality of pickled cowhide dehaired by scalding, singeing and enzyme has been made using the sensory evaluation system. Pickled cowhides dehaired by scalding, singeing were with deeper color, relatively higher fat concentration and better falvor, but poor in hardness and chewy.