Effect of fermentation on color characteristics and metabolite profiles of purple potato flour

The effect of fermentation on color characteristics and metabolite profiles of purple potato flour (PPF) were evaluated. The results showed that fermentation had a significant effect on the color attributes of samples. The bioactive compounds in PPF were identified using untargeted ultra-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-QTOF/MS). There were 63 compounds found in unfermented PPF (UF), while fermented samples showed more abundant compounds, including 69 compounds in naturally fermented PPF and 73 compounds in lactobacillus fermented PPF. The quantitative results showed that bioactive compounds with larger molecular weight decreased, but small molecules with high bioavailability increased after fermentation. The levels of caffeic acid, ferulic acid, and kaempferol in amylolytic L. plantarum CGMCC 14177 fermented PPF (ALF) were more than 3 times higher than those in UF. Foodomics analysis indicated that natural fermentation and lactobacillus fermentation had obvious differences in the conversion effect of metabolites in PPF. Based on orthogonal partial least squares discriminant analysis, 17 key bioactive compounds affected by fermentation were screened. L. plantarum CGMCC 15358 and CGMCC 14177 showed similar conversion effects on bioactive compounds, and their marker metabolites were trihydroxyoctadecenoic acid isomer 2, caffeic acid, 12,15-octadecadienoic acid methyl ester, and lactic acid.