Effect of batch and continuous thermosonication on the microbial and physicochemical quality of pumpkin juice

The study investigated the use of batch and continuous thermosonication for pasteurization of pumpkin ( Cucurbita moschata ) juice emphasizing on its microbial, physicochemical and sensorial quality parameters. Batch thermosonication (40, 50, 60 °C, 37 kHz, 150 W) of pumpkin juice was compared with the ultrasonication (23 °C) and conventional heat treatments (40, 50, 60 °C). For batch thermosonication, maximum inactivation of Escherichia coli K-12 was 6.62 ± 0.00 log cfu/mL, meanwhile, it was 3.64 ± 0.19 log cfu/mL for heat treatment. In addition, only 0.37 ± 0.21 log cfu/mL inactivation in E. coli K-12 was obtained by ultrasonication. The designed continuous thermosonication system (0.029 L/min, 60 °C) reduced E. coli K-12 by 6.23 ± 0.34 cfu/mL log after cycle 3 (34.15 min of processing). Color properties (L*, a*, b*, ∆E), pH, total titratable acidity, total soluble solids content, turbidity and non-enzymatic browning index were determined for batch and continuously thermosonicated, ultrasonicated and heat-treated pumpkin juices. Total color change of continuously thermosonicated samples were higher than the batch thermosonicated (60 °C) ones but, lower than the conventional heat treated (60 °C) samples. Sensory panel showed general acceptance scores of fresh, batch (60 °C) and continuously thermosonicated pumpkin juice samples have no significant ( P  < 0.05) difference. Continuous treatment results supported by the batch ones revealed that thermosonication could be effectively used for pasteurization of pumpkin juice producing a safe product with minimum changes in physicochemical and sensorial properties.