Effects of microwave combined with ultrasound treatment on the pasteurization and nutritional properties of bottle gourd (Lagenaria siceraria) juice

Abstract

This present study revealed the effectiveness of a combined microwave-ultrasonic pasteurization system on Listeria monocytogenes in bottle gourd juice (BGJ). Response surface methodology based on the central composite design was employed for optimization with microwave power (W), microwave-induced temperature (MT) (°C), ultrasound amplitude (UA) (%), and ultrasound exposure time (UT) (min) as the independent factors. Microbial cell viability, total phenolic content, total terpenoid content, and antioxidant activity were considered as the dependent factors. MT, UA percentage as well as ultrasonic exposure time were found to be most effective in reducing L. monocytogenes count. The ideal condition was 70°C temperature; 750 W microwave yield power, 80% amplitude, and 15 min of UT in which about 5 log decrease of L. monocytogenes count was observed. Furthermore, microwave and ultrasound processed juice showed superior antioxidant activity, vitamin content, storage activity, and physicochemical parameters as compared to conventionally processed juice. Practical applications The combined treatment of microwave and ultrasound turned out to be a very effective technique for pasteurization of BGJ. The technique was efficient enough to reduce heat-resistant bacteria such as Listeria monocytogenes. The technique can be further scaled up for pilot plant followed by industrial use as it proved to be better than the conventional methods of pasteurization. The functional parameters of the juice were very much retained in the sample pasteurized by the combined technique.