Evaluation of the spoilage heterogeneity of meat-borne Leuconostoc mesenteroides by metabonomics and in-situ analysis.

Leuconostoc mesenteroides are generally recognized as a group of specific spoilage organisms in meat and poultry products, which cause acidification and blown pack spoilage of meat. In this study, a total of 6 representative strains selected from 55 L. mesenteroides isolated from spoiled meat were tested to evaluate the spoilage ability by metabonomics and in-situ analysis. The intra-species spoilage heterogeneity was observed. The results showed that the acidifying and gas production capacity of L. mesenteroides was distinct between in broth and on meat. The pH of inoculated MRS broth was 1.38 to 1.49 units lower than that of the sterile broth and the height of gas column in Durham tube ranged from 8 mm to 11 mm at 72 h, all significantly different from the sterile group. Metabonomic analysis revealed that the main produced organic acids were myristic acid, butyric acid, lactic acid, valeric acid and enoic acid. It also illustrated that the UHPLC-MS/MS profiles of L4 and L5 was distinct from the other strains. In terms of meat inoculated with L. mesenteroides, most pH values did not show significant difference from that of the meat without inoculation, and vacuum packaging distension was not observed. Increase of TVB-N was very limited as well. The growth rate of L2, L4 and L5, as well as the pH changes of L3 and L6, varied wildly between different growth matrix. The differences between L5 and the other strains were the most obvious. The growth rate of L5 was the highest in vitro but the lowest in situ, and its acid- and gas-producing rate was relatively lower than that of the other groups. The results exhibited that it is limited to judge the bacteria-derived meat spoilage only by in-vitro growth. What should be focused on is the spoilage strengths in situ rather than the pure standard culture. In conclusion, the present study analyses profiles related to growth, acidification and gas production of L. mesenteroides in vitro and in situ, and provides references for emphasis on future research to reduce the loss of meat in consequence of spoilage.