Effects of CFSs produced by lactic acid bacteria in combination with grape seed extract on the microbial quality of ready-to-eat baby leaf vegetables

Abstract

The effects of the combined use of cell-free supernatant (CFS) and grape seed extract (GSE) in inhibiting the growth of pre-existing and inoculated foodborne bacteria on mixed, ready-to-eat (RTE) baby leaf vegetables were examined. Lactobacillus brevis WK12 and Leuconostoc mesenteroides WK32 produced significantly more acetic and lactic acid than citric, malic, succinic, or fumaric acids after 24 h of fermentation. The inhibition zone sizes observed when Lactobacillus brevis WK12 and Leuconostoc mesenteroides WK32 CFSs and 0.1% GSE were used in combination were much greater than those observed when either of the CFSs alone was used on agar plates. The application of 5% CFS from Lactobacillus brevis WK12 or Leuconostoc mesenteroides WK32 in combination with 0.1% GSE reduced the total counts of aerobic mesophilic bacteria, coliforms, and yeasts/molds in RTE baby leaf vegetable samples by 2.01, 1.74, and 1.87 log CFU/g, respectively, compared with those determined in the control. Combined CFS and GSE treatment reduced Escherichia coli O157:H7 and Listeria monocytogenes counts by 1.72 and 2.89 log CFU/g, respectively. These results suggest that the combined CFS and GSE treatment may act as a natural disinfectant, enhancing the safety of RTE baby leaf vegetables.

Keywords

• antimicrobial activity
• baby leaf vegetable
• grape seed extract
• lactic acid bacteria
• sanitizer