Study On Processing Of Potato Beverage By Lactic Acid Fermentation

In this study, as raw material, potato was fermented by lactic acid bacteria after being pulping, gelatinization, liquefaction, saccharification and mixing, to process beverage with activated lactobacillus. The beverage contains both the nutrients of potato and the fermentation flavor. The main research contents and results are as follows:The optimal liquefaction condition is:α-amylase dosage is 0.4%, reaction temperature is 55℃, reaction time is 50min, pH value is 6.8. The optimal saccharification condition is:glucoamylase dosage is 0.2%, reaction temperature is 55℃, reaction time is 3 hours, pH value is 4.5.Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus casei, Bifidobacterium were used as fermentation strains, and researched on the acidogenicity and viable count of different strains. In the single strain fermentation experiment, the acidogenicity of Lactobacillus bulgaricus is the best, the viable count of Lactobacillus casei is the highest. In the compound strains fermentation experiments, considering acidogenicity and viable count, the best strain is the combination of Lactobacillus bulgaricus, Lactobacillus casei and Bifidobacterium, which is confirmed as the compound fermentation strains of the potato beverage.The present study researched the effects of the strains ratio, inoculum size, fermentation temperature on the fermentation result. The results showed that the fermentation temperature was the main factor; The optimal fermentation condition is:the strains ratio(Lactobacillus bulgaricus:Lactobacillus casei:Bifidobacterium) is 1:1:1, the inoculum size is 6%, fermentation temperature is 40℃, the final fermentation acidity is 50.7°T, the viable count is 1.5 x 109CFU/mL.This study researched the effects of the variety and dosage of stabilizers on the stability of the potato fermented beverages. The results showed that sodium alginate works best to improve the stability, the optimum dosage is 0.07%. Taking sensory score and stability index into consideration, determined the optimal formula for the lactic acid fermented beverages:the sucrose content is 3%, fermentation time is 10h, the dosage of sodium alginate is 0.09%.46 kinds of volatile flavor compounds were detected in fermented potato beverage by using solid-phase microextraction(SPME) and gas chromatography-mass spectrometry (GC-MS) method, including 14 ester species,9 aldehyde species,4 alcohol species,7 ketone species,1 acid species,6 aromatic heterocyclic species,1 kind of sulfur-containing compounds and 3 kinds of hydrocarbon compound.With the extension of storage time, the acidity showed a trend of increase in the lactic acid fermented beverages, the viable count reduced continually. Combined with sensory quality of the fermented beverages, its storage period could reach 21 days. At the moment the beverage’s viable count is 8.7×107CFU/mL, acidity is 69.5°T.