Bioactive compounds, volatile compounds, rheological properties and bacteriostatic activities of fig juices with oligosaccharides supplementation fermented by Lactiplantibacillus plantarum

Abstract

The objective of this study was to investigate the effects of Lactiplantibacillus plantarum fermentation on the bioactive compounds, volatile compounds, rheological properties and bacteriostatic activities of fig juices supplemented with oligosaccharides, namely fructooligosaccharides (FOS), galactooligosaccharides (GOS), isomaltooligosaccharides (IMO), xylooligosaccharides (XOS), stachyose (SOE) and mannanoligosaccharides (MOS). Results showed that SOE, FOS and IMO supplementations stimulated the proliferation of Lactiplantibacillus plantarum, especially for SOE, exhibiting the highest viable bacterial counts (9.84 log CFU/mL). Oligosaccharides supplementation accelerated the conversion of carbohydrates to organic acids, and increased the total contents of flavonoid (TFC) and carotenoid (TCC) during fermentation, of which FOS exhibited the greatest increases in TFC (66.28 mg RE/L) and TCC (0.032 mg/L). Furthermore, the highest levels of DPPH RSA (65.88%) and ABTS RSA (66.24%) were found in fermented fig juice supplemented with MOS, while the highest level of FRAP (0.97 mmol Trolox/L) and protocatechuic acid (6.97 mg/L) was observed in that with GOS. The total contents of alcohols and esters were significantly increased, while aldehyde content was decreased by oligosaccharides supplementation. In addition, oligosaccharides supplementation decreased the apparent viscosity of fermented juices. Fermented juices supplemented with FOS exhibited dramatically effective inhibition against Escherichia coli, Staphylococcus aureus and Listeria monocytogenes, due to the ruptures of cell surfaces and collapse of cellular structure. According to Pearson's correlation analysis, protocatechuic acid content was significantly and positively correlated with bacteriostatic activities. It was suggested that FOS should be a better probiotic additive for the preparation of fermented fig juice.