Ultrasound as a pre-treatment in millet-based probiotic beverage: It's effect on fermentation kinetics and beverage quality

Abstract

Recently, non-dairy based probiotic beverages has a progressive market, in this study the effect of ultrasound on the fermentation kinetics and quality of millet-based probiotic beverages (MPB) was carried out. White finger millet (Eleusine coracana L.) variety KMR-340 was used in this study. Two treatment conditions including ultrasound (US) treatment before inoculation (0.53–1.59 W/mm2 for 5–15 min) and US treatment after inoculation (0.21–0.35 W/mm2 for 1–5 min) were taken as a pretreatment. The optimum condition for US treatment before inoculation was identified as 0.99 W/mm2 intensity and 11.09 min, in the case of US treatment after inoculation, it was identified as 0.29 W/mm2 intensity and 2.63 min treatment time of US treatment. In the US treatment after inoculation, requires the lowest fermentation time which is 2.6-fold times lower than the untreated samples. Structural changes in millet protein and other molecules by the US alter the techno-functional behavior of MPB like water holding capacity (WHC) and viscosity. The Weibull model explains the fermentation kinetics of MPB, the rate constant of lactic acid was higher in US treatment after inoculation explaining the probiotic microbial proliferation by low-intensity US treatment. During fermentation, change in lactic acid follows three stages: rapid change, constant period, and gradual change. These findings prove that changes in US treatment highly affect the fermentation kinetics of probiotic microbes, and the US treatment can be used to alter the physicochemical changes in probiotic beverages.