Abstract
In this study, a newly isolated Pediococcus acidilactici F3 was used as probiotic starter for producing fermented soymilk to enhance antioxidant properties with high antimicrobial activity against food-borne pathogens. The objectives of this study were to investigate optimized fermentation parameters of soymilk for enhancing antioxidant property by P. acidilactici F3 and to assess the dynamic antimicrobial activity of the fermented soymilk during co-culturing against candidate food-borne pathogens. Based on central composite design (CCD) methodology, the maximum predicted percentage of antioxidant activity was 78.9% DPPH inhibition. After model validation by a 2D contour plot, more suitable optimum parameters were adjusted to be 2% (v/v) inoculum and 2.5 g/L glucose incubated at 30 °C for 18 h. These parameters could provide the comparable maximum percentage of antioxidant activity at 74.5 ± 1.2% DPPH inhibition, which was up to a 23% increase compared to that of non-fermented soymilk. During 20 days of storage at 4 °C, antioxidant activities and viable cells of the fermented soymilk were stable while phenolic and organic contents were slightly increased. Interestingly, the fermented soymilk completely inhibited food-borne pathogens, Salmonella Typhimurium ATCC 13311, and Escherichia coli ATCC 25922 during the co-culture incubation. Results showed that the soymilk fermented by P. acidilactici F3 may be one of the alternative functional foods enriched in probiotics, and the antioxidation and antimicrobial activities may retain nutritional values and provide health benefits to consumers with high confidence.