Biochemical and microstructural characteristics of meat samples treated with different plant proteases
This study was conducted to compare the efficiency of different plant proteases for changing biochemical and microstructural characteristics in muscle foods. The meat samples from chicken, giant catfish, pork and beef were treated with four types of proteolytic enzymes: Calotropis procera latex proteases, papaya latex proteases, commercial papain and bromelain at the concentrations of 2 × 103 to 6 × 103 activity units/100 g of muscle. The pH, collagen solubility, trichloroacetic acid (TCA) soluble peptides, protein patterns and muscle microstructures of the treated samples were evaluated after 24 h at 4°C. A decrease of muscle pH in chicken, giant catfish and pork was observed when the enzymes were added (p < 0.05). A significant increase in collagen solubility was also found in all of the muscle samples (chicken increased from 37.64 to 83.59%; giant catfish increased from 52.82 to 84.14%; pork increased from 14.34 to 86.78; and beef increased from 26.02 to 86.18%; p < 0.05). An increase in TCA-soluble peptides (from 0.90 to18.53 μmole/g sample), and myofibrillar protein degradation was observed in all of the enzyme treated samples as compared to the control (p < 0.05). The electrophoretic pattern of the muscle proteins also revealed extensive proteolysis and reduction of protein bands in all of the treated samples. At the microstructural level, tissue fibers were broken, and the connections between the sarcolemma and the myofibrils were loosened when each enzyme was applied. When comparing all proteolytic enzymes used, papaya latex proteases showed the highest hydrolysis activity in all muscle types, which was followed by C. procera latex proteases, commercial papain, and then bromelain. The results show that these proteolytic enzymes could be used as an effective meat tenderizer.
Key words: Proteases, muscle foods, collagen, tenderization, toughness.