Abstract: The purpose of this study was to investigate the effect of fermentation conditions on the acidity and viable bacterial count of a beverage developed from quinoa malt fermented with lactic acid bacteria. Mixed starter cultures of Lactobacillus plantarum and Lactobacillus casei were used for the fermentation. One-factor-at-a-time method and response surface methodology were used to explore the effect of starter culture composition, inoculum amount and fermentation time on fermentation. A ratio of L. plantarum to L. casei of 2.5:1, an inoculum amount of 3% and a fermentation time of 10.3 h were found to be optimal. Under these conditions, the acidity of fermented quinoa malt was 85.32 °T and the viable count was 9.21 (lg(CFU/mL)), which were in good agreement with the predicted values. The result showed that homogenized quinoa malt was suitable for the growth of lactic acid bacteria.

Key words: quinoa malt, fermentation process, lactic acidity, viable count, response surface methodology