Process Optimization of Sweet Potato Juice Fermented by Probiotics

The taste and nutritional values of sweet potato juice could be improved after fermented by probiotics.In the present study, the sweet potatoes juices were prepared using yellow meat variety ‘Yunshu 9801’ and purple meat variety ‘Luozi 4’ as raw materials and fermented by Polysaccharide actinomyces, subsequently, the effects of fermentation time, fermentation temperatures, substrate concentrations, inoculum amounts and sucrose additions on juices quality were studied. Then response surface design of 4 factors（fermentation temperature, fermentation time,substrate concentrations and inoculation amounts） and 3 levels was constructed on the basis of single-factor experiments, and the quadratic regression equation of sensory evaluation on fermented sweet potato juice was established. Results showed that the optimum fermentation conditions of ‘Yunshu 9801’were obtained as follows: substrate concentration of 30.0%, inoculation amount of 10.4%, fermentation temperature of 34.1 ℃, fermentation time of 36.0 h and sucrose addition of 10.0%. The optimal fermentation conditions of ‘Luozi 4’were determined as follows: substrate concentration of 39.6%, inoculation amount of 9.8%, fermentation temperature of 32.3 ℃, fermentation time of 31.0 h and sucrose addition of 10.0%. The selection of varieties and the optimization of technology would provide guidance for development and application of fermented sweet potato juice.