Effect of ultrasound treatment on white finger millet-based probiotic beverage

Abstract

This study aimed to examine the impact of ultrasound on white finger millet-based probiotic beverages (WFMPB). The process variables such as amplitude and treatment time for ultrasound treatment were obtained using response surface methodology. Ultrasound (US) treatments were applied before and after the inoculation to trigger the culture growth. US-treated WFMPB were evaluated for total phenolic content, flavonoid content, antioxidant activity, reducing sugars, viable cell count, particle size, sugar analysis, and volatile organic compounds after the fermentation process and compared with the control (sterilized). The total phenol content, total flavonoid content, antioxidant activity, and reducing sugar content of US-treated samples were significantly increased. Glucose, fructose, sucrose, galactose, and maltose were observed to be the major sugars in WFMPB. The particle size of US-treated WFMPB was observed to be smaller than those in the non-sonicated WFMPB. Viable counts of US treatment before inoculation (8.56 log CFU/ mL) and after inoculation (8.31 log CFU/ mL) were higher than the control (7.76 log CFU/ mL). Collectively, the present study suggested that millet as a substrate for probiotic beverage production could overcome the concerns regarding high cholesterol content and lactose intolerance of dairy products in developed countries, as well as economic concerns in developing countries. In the future, the proliferation kinetics of probiotics during the fermentation and storage period can be studied. Thus, the fermented millet beverage with L. rhamnosus is a good and healthy probiotic-rich functional food.