Lactic acid fermentation of anthocyanin-rich sweet potato (Ipomoea batatas L.) into lacto-juice

Sweet potato (SP) is an important root crop grown all over the world and consumed as a vegetable, boiled, baked or often fermented into food and beverages. The grated SP roots [non- boiled and fully boiled (boiled in water at 100 degrees C for 15 min) were treated with 0.05% of commercial pectinase enzyme (Pectinex, Novoenzyme) in order to extract the juice. The fresh juice was inoculated with Lactobacillus plantarum MTCC 1407 culture at 28 +/- 2 degrees C for 48 h to produce lacto-juice (LJ). The anova analysis of analytical data revealed that there was significant effect of boiling conditions (fully boiled and non-boiled) on pH [F (1, 4) = 220.5, P < 0.001), TA [F (1, 4) = 78.89, P < 0.01], starch [F (1, 4) = 26.63, P < 0.01), total sugar [F (1, 4) = 61.36, P < 0.01) and anthocyanin [F (1, 4) = 32.86, P < 0.01) but not on reducing sugar [F (1, 4) = 2.48, P = 0.19). Sensory evaluation rated the SP LJ acceptable based on texture, taste, aroma, flavour and after taste. LJ prepared from fully boiled roots with 10% cane sugar was most preferred by a consumer's panelist based on Linear Discriminant Analysis. Principal component analyses (PCA) reduced the seven original analytical variables to three independent components (factors), which accounted for 99.9% of the total variations. Similarly, six original sensory variables were reduced to two independent components, which accounted for 65.7% of the total variations.