Bioprocess Improvement for fermentation of pigmented Thai glutinous rice-based functional beverage (Sato) with superior antioxidant properties

Abstract

The fermentation of steamed rice with a microbial starter yields the unique traditional alcoholic beverage known as Sato, which is widely consumed in many provinces of Thailand. Both rice variety and fermentation conditions are crucial factors in a rice-fermented beverage that contribute to the final product's quality and functionality. This study was conducted to characterize the rice-based beverage fermented from pigmented and non-pigmented glutinous rice and to optimize the bioprocess of rice-fermented beverage production. Glutinous rice varieties, including white glutinous rice, white-brown glutinous rice, germinated white-brown glutinous rice, and germinated black-brown glutinous rice, and a local microbial starter (namely, Nan starter) were used for rice-fermented beverage production through solid-state fermentation (SoSF) for 3 days and subsequently submerged fermentation (SmF) for 7 days. During the SoSF and SmF processes, key fermentation parameters, including fermentation temperature (30–40 °C) and starter dosage (0.2–1.0% w/w), were then optimized. The rice-fermented beverage produced from germinated black-brown glutinous rice had a preferable alcohol concentration (3.93%), as well as better levels of antioxidant activity (54.64%), providing a superior overall acceptable sensory characteristic compared to the rice-fermented beverage produced from non-pigmented rice. Under optimized conditions at a temperature of 30 °C and a starter dosage of 1.0%, the rice-fermented beverage had a higher antioxidant activity of 67.29% with the desired characteristics and sensory properties. This study demonstrated that the developed products might contribute to the establishment of commercially viable rice-fermented beverages with health benefits and help promote the functional food industry.