Probiotics Biotransformation Of Purple Sweet Potato Anthocyanins And The Application In Yogurt Fermentation

Purple sweet potato(Solanum tuberdsm)contains large amounts of purple sweet potato anthocyanin(PSPA),and the natural antioxidant ability of anthocyanins is comparable to vitamin C,but the study found that the anthocyanin bio-metabolic utilization is not ideal in the human body.The difference of absorption and utilization of anthocyanin metabolites among different individuals is caused by the difference of their intestinal microflora.The study found that after feeding pigs and human anthocyanins,protocatechuic acid content increases in their blood or urine,which may be related to the biotransformation intestinal flora.Epidemiological studies have shown that PSPA and protocatechuic acid are effective in preventing the occurrence of cardiovascular disease or cancer.The purpose of this paper is to study probiotic biotransformation of PSPA,and try to screen efficient lactic acid bacteria that can transform PSPA to protocatechuic acid.Than,to study the fermentation process of Kefir yoghurt with PSPA,and optimize the proportion of fermented bacteria starter.The results of this paper:(1)The concentration of 703.7mg/L PSPA was extracted from 25 grams of purple sweet potato starch by ultrasonic extraction method with acidified ethanol extractant(0.1% HC1/95% ethanol,v/v = 40/60).Adsorption of anthocyanin was carried out with AB-8 macroporous resin at pH 4 for 30 min,and then anthocyanin was dissociated with 60% ethanol.The color of anthocyanin extract was increased and the freeze-drying anthocyanin‘s Viscousstatus is improved.(2)Established a method using the phosphate solution-lactic acid bacteria whole cell transformation of PSPA into protocatechuic acid.With detected the content of protocatechuic acid by HPLC,screened two strains efficient lactic acid bacteria,Lactobacillus rhamnosus YYJP-2 which can transform PSPA to protocatechuic acid.In the transformation product of one of the Lactobacillus rhamnosus YYJP-2 the protocatechuic acid was 2.27 ~ 3.3 mg/mL.(3)The result of the orthogonal test:Sugar 7%,Chr.Hansen KEFIER 1 starter 0.15g/L,Lactobacillus rhamnosus YYJP-2 freeze-dried powder 0.05mg/L~0.075mg/L,at 37?fermentation for 12 hours.The yogurt in this craft condition is characterized by refreshing texture,more vivid colors,high water retention ability,and higher antioxidation than ordinary yogurt.