No abstract

Trypsin was extracted from the intestines of tilapia and purijied 136-fold on the basis of amidase activity by a sequence of ammonium sulfate fractionation, acetone precipitation and afinity chromatography on soybean trypsin inhibitor bound to 4.0% beaded agurose. The purijied trypsin exhibited higher esterase than amidase activity at its optimum pH of 9.0. The enzyme was stable in the range of pH 7-9. The optimum temperature for enzyme activity was 40C and the Q,, for enzyme activity was 1.7 from 20C-30C and 30C-40C. The Arrhenius energy of activation was 8.9 and 8.7 kcal. /mol respectively, for the ranges of 20C-30C and 30C-40C.

This study was to evaluate the activity of peroxidase, polyphenoloxidase, pectin methyl esterase and protease as well as the proximate chemical composition and quality parameters of cactus pear and papaya which were dried by different methods and stored for 6 months. Our findings revealed that the highest moisture content was recorded in osmofreeze drying of papaya and cactus pear. On the other hand, the browning index of oven dried papaya and cactus pear was higher than those dried with osmotic dehydration and osmofreeze drying. The less activity of peroxidase was recorded in osmofreeze drying of papaya and cactus pear. Also, the highest reduction of polyphenoloxidase activity was noticed in osmofreeze drying methods. While oven dried papaya recorded the highest activity of pectin methyl esterase pectin (0.34 %), complete inactivation was shown in other dried methods after 6 months of storage at 4 ±1℃. Different dried methods of papaya caused to reduce the activity of protease, moreover, complete inactivation was observed after 3 months from storage. The quality parameters for sensory evaluation of dried cactus pear and papaya demonstrated that osmo-freeze drying was more favorable to preserve samples followed by osmotic dehydration and oven drying.