Preparation of purple sweet potato beverage fermented by Lactobacillus plantarum

Taking purple sweet potato as main material, the technology of purple sweet potato beverage fermented by lactic acid bacteria was studied. The results showed that the ratio of purple sweet potato and water for pulping was 1∶5. In order to obtain sufficient starch hydrolysis, the purple sweet potato pulps were treated with6U/100 m L α-amylase at 60℃ for 20 min, and then treated with 55U/100 m L glucoamylase at p H4.5 for 90 min.By using orthogonal experimental design, the optimum fermentation conditions were determined as follows:inoculums amount 4%, temperature 37℃ and time 14 h. The optimum formula was 8% sucrose, 0.1% citric acid, 0.02% xanthan gum, 0.02% CMC-Na and 0.02% PGA.