酶法制备紫马铃薯汁及其乳酸菌发酵特性

本文以紫马铃薯为原料,通过酶法制备富含花色苷的紫马铃薯汁,分别使用干酪乳杆菌、保加利亚乳杆菌及植物乳杆菌三种乳酸菌对其进行发酵,研究烫漂时间、酶用量对紫马铃薯汁出汁率、花色苷、还原糖含量的影响及发酵过程中pH、花色苷、总酚含量、糖组分、有机酸、DPPH·清除能力等变化。结果表明:紫马铃薯经烫漂护色2.5 min时出汁率最高。烫漂时间对紫马铃薯汁的花色苷含量影响极为显著,烫漂2.5 min时花色苷含量比未经烫漂处理的提升了7.7倍。经高温α-淀粉酶(20 U/g)、糖化酶(200 U/g)酶解处理后的紫马铃薯汁出汁率为69.80%±3.85%,总酚含量1136.7±33.76 mg/L,花色苷含量为218.25±1.89 mg/L。紫马铃薯汁经乳酸菌发酵后pH逐渐下降,并产生大量的乳酸,产酸能力大小依次为保加利亚乳杆菌 > 植物乳杆菌 > 干酪乳杆菌,蔗糖、葡萄糖和果糖在发酵过程中均作为底物被乳酸菌消耗,发酵48 h后花色苷、总酚、DPPH·清除能力分别下降了11.33%~17.82%、6.22%~7.73%、24.23%~27.62%。抗氧化活性下降与花色苷和总酚含量的减少有关。

Enzymatic Preparation of Purple Potato Juice and Its Fermentation Characteristics of Lactic Acid Bacteria

In this paper,purple potato juice rich in anthocyanins was prepared by enzymatic method. Lactobacillus casei,Lactobacillus bulgaricus and Lactobacillus plantarum were used to ferment purple potato juice. The effect of blanching time,high temperature α-amylase dosage on the yield and anthocyanin content of purple potato juice and changes of pH,anthocyanin,total phenol content,sugar component,organic acid and DPPH scavenging capacity during fermentation were studied. The results showed that the purple potato had the highest juice yield after blanching and color protection for 2.5 min. The blanching time had a significant effect on the anthocyanin content of purple potato juice. The anthocyanin content was 7.7 times higher than that without blanching when blanching for 2.5 min. With the treatment of high temperature α-amylase(20 U/g)and saccharification enzyme(200 U/g),the yield of purple potato juice was 69.80%±3.85%,the total phenol content was 1136.67±33.76 mg/L,and the anthocyanin content was 218.25±1.89 mg/L. The pH value of purple potato juice gradually decreased after fermentation by lactic acid bacteria,and a large amount of lactic acid was produced. The acid production capacity was in the order of Lactobacillus bulgaricus > Lactobacillus plantarum > Lactobacillus casei. Sucrose,glucose and fructose were consumed by lactic acid bacteria as substrates during fermentation.The anthocyanin,total phenol and DPPH·clearing ability decreased by 11.33%~17.82%,6.22%~7.73%,24.23%~27.62%,respectively after 48 h of fermentation. The decrease of antioxidant activity is associated with that of anthocyanin and total phenolic content.