Nutritional, microbial and physicochemical changes in pear juice under ultrasound and commercial pasteurization during storage

In this study, the microbial and nutritional aspects of pear juice with conventional or ultrasound (US) treatment during storage at 4  °C were studied. The conventional pasteurization was 95 °C for 5 min while US-pasteurizations (frequency 30 kHz, amplitude 70%) were 25, 45, and 65 °C for 10 min, under a probe sonicator (750 W). Control, US25 and US45 had shelf lives of 9, 12, and 15 days respectively. Ascorbic acid, total phenols, total anti oxidant capacity, and cloud value decreased in all treatments while pH, acidity, and sugars remained stable. Both treatments (P95 and US65) remained viable after 21 days of storage, however, loss of bioactive compounds in P95 (16.39%) was significantly higher than that of US65 (7.44%), indicating US-pasteurization a promising pear juice processing technology at low temperature, retaining bioactive compounds, meeting safety standards, and increasing shelf life. Practical applications Complete microbial and enzymatic deactivation is achieved at commercial thermal pasteurization techniques, but these elevated temperatures cause losses in nutritional and sensory attributes of the end product. While microbial and enzymatic deactivation in pear juice was achieved at lower temperature using thermosonication in the present study. The low temperature pasteurizations exhibited higher retention and availability of bioactive compounds than the traditional high temperature pasteurizations over the studied shelf life period. The findings of the study would pave way for the commercial processing of pear juice with improved quality and shelf life.