Effects Of Addition Of Different Proteases During The Curing Process On The Quality Of Pork Paste And Pork Jerky

Pork jerky is a typical traditional Chinese meat product. It is a dry cooked meat productwith a unique technique, good conservation capacity, portability, great taste, and has gainedmuch popularity and acceptance. The process of the meat paste is a precursor of a variety ofmeat products production, and helpful to set new processes or improve existing processes ofpork jerky. In this work, the frozen meat properties, the influence of different proteases onfrozen meat properties and its mechanism research, effects of both papain andtransglutamianse adding into meat paste at the same time on pork jerky properties were allsystematically evaluated. Conclusions are as following:Changes of pork quality in the frozen period (0-120d,-18℃) were evaluated. Resultsshowed that luminance value decreased, both redness value and yellowness value increased(p<0.05). This indicated that pork became darker during the frozen storage. As time went on,chewiness, springiness and cohesiveness all decreased significantly as a whole (p<0.01).Cooking loss increased during the storage (p<0.01). Total protein solubility, myofibrillarprotein solubility and sarcoplasmic protein solubility all decreased (p<0.01). There was asignificant increase in the TBARS (thiobarbituric acid reactive substances) value (p<0.05),indicating that the levels of lipid oxidation of meat paste became more serious. Therefore,pork quality decreased during the frozen storage.Effects of the addition of proteases (papain, neutrase, protamex) in the curing process onthe quality of frozen pork were evaluated. The results showed that, with the addition ofproteases, luminance value of frozen pork increased significantly (p<0.05), and proteasescould inhibited both redness value and yellowness value of cooked meat paste increasing, andreduced the growth rate of yellowness value of raw meat paste (p<0.05). It indicated thatproteases could improve the lightness of meat paste, and inhibited meat paste getting darkerand more yellow. Springiness, chewiness and cohesiveness of the frozen pork increasedsignificantly (p<0.01), suggesting that the addition of proteases during the curing process ofpork could significantly improve their texture properties. Cooking loss of the frozen porkdecreased with the addition of proteases (p<0.01). Results from sensory evaluation of meatpaste based on the fuzzy mathematics method showed that,31.6%consumers recognized the control group,33.3%consumers recognized the group with papain,36.8%consumersrecognized the group with protamex, and33.3%consumers recognized the group withneutrase. The levels of lipid oxidation of meat paste were significantly inhibited characterizedby the decreases in the TBARS value, POV (peroxide value) compared with the controlgroup.The mechanism of the influence of proteases on the meat paste was studied. Resultsindicated that, during the curing process, with the addition of different proteases, theexperimental group exhibited significantly higher antioxidant capacities evaluated byreducing power, DPPH·clearance, and oxygen radical absorbance capacity (ORAC) than thecontrol group. The experimental group with the addition of papain had the most obviouseffects (p<0.01). During the storge, the addition of proteases could effectively reduce thespeed of the meat protein oxidation characterized by the slower decreases in sulphydrylcontent compared with the control group. Meat protein degraded with the addition ofproteases chracterized by the presentation of SDS-PAGE (sodium dodecyl sulfatepolyacrylamide gel electrophoresis), the molecular weight of peptides, free amino acid. Thenewly formed small molecules such as amino acids and other substances due to the meatdegradation might exhibited antioxidant capacities, it was indicated that these smallmolecules could reduce the speed of lipid oxidation, thus might reduced the speed of proteinoxidation to a certain degree.Effects of papain content on the quality of meat paste were was studied, and TPAproperties, cooking loss and storage properties were determined. Results showed that, withdifferent content of papain adding into the meat paste, cooking loss decreased dramatically(p<0.01). As addition content between0and0.08%, the cooking loss decreased withincreased addition of papain. However, until the papain content was0.08%, the cooking lossincreased. With papain content increasing, hardness of meat paste decreased dramatically.Papain could inhibit redness value of meat paste decreasing, so to maintain meat color stable.Papain could inhibit fat oxidation of meat paste characterized by the decreases in TBARSvalue, but0.02%BHT was a better choice. According to the sensory quality including odor,color and the overall acceptability, the sense scores of the experimental group were higherthan the control group. Papain, TGase and salt were added into the meat paste during the curing process. Onbasis of the single factors test, effects of enzymes content, baking time and mode of bakingon the quality of pork jerky were studied. The yield of pork jerky, hardness and sensoryproperties were evaluated. The optimal conditions were that0.04%papain was added, andTGase content was0.06%, salt content was2.0%, baking time was5h, baking method wasusing the vacuum drying chamber under a constant temperature of65℃. In addition, Aw(water activity) was not only influenced by water content, and during the experiment, watercontent could be replaced byAw as the parameter, and the optimalAw was≦0.75.