Microbial and enzymatic inactivation in fresh pear juice were studied under conventional and
ultrasound-pasteurizations. The ultrasound-pasteurization conditions were 25, 45 and 65 C for 10 min
using a 750 W probe sonicator (frequency 20 kHz and amplitude 70%) while conventional pasteurization
conditions were 65 C for 10 min and 95 C for 2 min. Complete inactivation of enzymes (peroxidase,
pectinmethylesterase and polyphenol oxidase) and microbes (total plate count, yeast and mould) were
observed in conventional pasteurization at 95 C but this treatment also showed highest losses of
ascorbic acid, total phenols, flavonoids and antioxidant capacity. Ultrasound-pasteurization at 65 C for
10 min showed the best results in retention of ascorbic acid and other phenolic compounds with significant
reduction in enzyme activities and complete inactivation of microbes. Values of pH, acidity and Brix showed no significant changes under conventional or ultrasound-pasteurization treatments. The
findings of the present study indicate that pasteurization at low temperatures in combination with ultrasound
can successfully be employed for commercial processing of pear juice with improved quality
Microbial and enzymatic inactivation in fresh pear juice were studied under conventional andultrasound-pasteurizations. The ultrasound-pasteurization conditions were 25, 45 and 65 C for 10 minusing a 750 W probe sonicator (frequency 20 kHz and amplitude 70%) while conventional pasteurizationconditions were 65 C for 10 min and 95 C for 2 min. Complete inactivation of enzymes (peroxidase,pectinmethylesterase and polyphenol oxidase) and microbes (total plate count, yeast and mould) wereobserved in conventional pasteurization at 95 C but this treatment also showed highest losses ofascorbic acid, total phenols, flavonoids and antioxidant capacity. Ultrasound-pasteurization at 65 C for10 min showed the best results in retention of ascorbic acid and other phenolic compounds with significantreduction in enzyme activities and complete inactivation of microbes. Values of pH, acidity and Brix showed no significant changes under conventional or ultrasound-pasteurization treatments. Thefindings of the present study indicate that pasteurization at low temperatures in combination with ultrasoundcan successfully be employed for commercial processing of pear juice with improved quality
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