Research on fermentation process optimization, antioxidant and hypoglycemic activity of pigmented rice lactic acid beverage

Objective: To develop pigmented rice lactic acid beverage with good antioxidant and hypoglycemic activity. Methods: Taking black and purple rice as the main material, the effect of mass ratio of purple rice to black rice, the addition amount of Lactobacillus bacteria, fermentation time and solid-liquid ratio on the sensory evaluation value, total phenolics content, ferric ion reducing antioxidant power （FRAP）, ABTS free radical scavenging ability, and the inhibition rate of α-glucosidase of pigmented rice lactic acid beverage were explored. Results: The optimal technology of pigmented rice lactic acid beverage was as follows: the mass ratio of purple rice to black rice was 1∶5, the solid-liquid ratio was 1∶8 （g/mL）, the addition amount of lactic acid bacteria was 5%, and the fermentation time was 40 h. Under these conditions, the sensory score of pigmented rice lactic acid beverage was 83.6±2.51, ABTS radical scavenging capacity was （145.02±7.88） mmol TE/g·DW, FRAP was （33.41±1.70） mmol Fe2+/g·DW, total phenolics were （4 208.78±281.26） μg GAE/g·DW, α-glucosidase inhibitory rate activity was （13.94±0.01）%. Conclusion: The pigmented rice lactic acid beverage possessed purplish red color, soft in taste, moderate in sour and sweet taste, with good antioxidant activity and α-glucosidase inhibition effect.