Effect of Chemical and Physical Dry-curing Parameters on Cathepsins B, H and L from Ostrich Muscle

The effects of curing agents (NaCl, nitrate, ascorbic acid and glucose) and processing parameters (pH, temperature and cooking temperatures) on cathepsins B, H and L activities were investigated. NaCl, nitrate, ascorbic acid and glucose exhibited different influences on ostrich cathepsin B, B+L and H activities. In the range 20-60gl(-1), NaCl inhibited cathepsin B+L and H activities. All three cysteine proteinase activities were inhibited by up to 8g ascorbic acid l(-1). With the exception of cathepsin B activity, which was inhibited by glucose, nitrate and glucose had very little effect on cathepsin B, B+L and H activities. Cathepsins B and D were active at 65 and 69°C and might play an important degradative role during the cooking of meat and meat products. Cathepsins B, B+L and H were optimally active at temperatures of 40-45°C and 50°C, and were still quite active at the low temperatures used in the dry-curing process; they showed maximum activity in the pH range 5·5-7. A simulation of the three stages of the dry-curing process of hams revealed that cathepsins B and B+L might play an important role throughout the complete process, whereas cathepsin H could only participate in the middle and at the end of the dry-curing process. Although ostrich cathepsins show many properties similar to those from other species, the present study also revealed some interesting distinguishing features.