Antimicrobial effect of koruk (unripe grape—Vitis vinifera) juice against Salmonella typhimurium on salad vegetables

To evaluate the antimicrobial activity of koruk (unripe grape—Vitis vinifera) juice, cucumber and parsley samples were inoculated with two Salmonella typhimurium strains namely S. typhimurium NRRL-B-4420 and S. typhimurium CCM 583 at the level of approximately 106 cfu/ml. The samples were treated with koruk juices produced by different methods (by using mortar and electrical blender) for 0, 15, 30 and 60 min. Salmonella cells were counted by using direct surface plating (on Tryptone Soya Agar, Bismuth Sulphite Agar or Xylose Desoxylate Agar with 50 ppm nalidixic acid; TSAN, BSAN or XLDN) and overlay plating (on TSAN/BSAN) methods. Counts on TSAN/BSAN or TSAN, BSAN and XLDAN were not significantly different (P > 0.05). So, further experiments were done with direct surface plating on TSAN and BSAN. Overall statistical analysis indicated that, the antimicrobial effect of koruk juice was found to be dependent on the culture strains and products used (P < 0.05). Koruk juice exerted an immediate antimicrobial effect contact with the test microorganisms causing 1–1.5 log cfu/g reductions in initial populations. However, cell reductions in samples exposed to koruk juice for 15, 30 and 60 min varied between 2 and 3.5 log cfu/g depending on the microorganism and test sample used. There was no significant difference in cell reduction in samples exposed to koruk juices for 15, 30 and 60 min (P > 0.05) whereas reduction obtained at 0 time differed significantly (P < 0.05). On the other hand, no significant differences were found between the antimicrobial effects of koruk juices prepared by different methods. Results of the study showed that koruk juice used as flavouring and acidifying agent in Turkish kitchens, may be considered to be an alternative potential antimicrobial agent at household level for salad vegetables.