Bael (Aegle marmelos) beverage pasteurization by non-isothermal heating with continuous microwave to achieve microbial safety

The efficacy of conventional thermal (batch) and continuous microwave (MW) heating to pasteurize bael beverage was examined by inactivating Escherichia coli, Listeria monocytogenes, Salmonella Typhimurium, Saccharomyces cerevisiae, their cocktail, and native microbial groups. Continuous-MW was operated at 2 kW power and 45–80 °C final temperature. For 25–90 °C beverage temperature, the fluid followed a laminar flow. Data were appropriately modelled using first-order kinetics. MW-heating effectively inactivated all microorganisms. S. cerevisiae was most resistant towards thermal inactivation under single (D_{70 °C} = 0.03 min) and cocktail scenario (D_{80 °C} = 0.014 min) and towards MW under cocktail scenario (D_{MW_67.5 °C} = 0.23 min). The resistance towards temperature rise was highest by L. monocytogenes. Based on lower z_MW-values, the thermal sensitivity of microbes improved under MW heating. Morphological alteration in microbial cells of S. cerevisiae & L. monocytogens reveals that the lethality of MW inactivation is mainly based on its thermal effects.

Industrial relevance

Bael fruit is a nutritious tropical fruit whose beverage is relished by consumers for its refreshing flavour and numerous health benefits. The food sector is presently concentrating on creating innovative, minimally processed goods that are ready-to-eat or handy, shelf-stable, and of higher quality. As an alternative to conventional thermal processing, several novel and sustainable processing methods are now being investigated. To determine if microwave processing is a suitable substitute for thermal processing, the inactivation of artificially inoculated microorganisms, their cocktail, and indigenous microorganisms in the bael beverage were examined in this work. Kinetic study, beverage rheology and changes in cell morphology were also studied. The study's findings indicate that continuous microwave technology can be a more suitable method of pasteurizing fruit beverages than conventional heating due to its >7 log reduction in a shorter time. Except for a few differences, the inactivation mechanisms of thermal and microwave are comparable.