Mixed starter of Lactococcus lactis and Leuconostoc citreum for extending kimchi shelf-life

To develop a starter culture system for improving the shelf-life and quality of kimchi, we prepared a mixed starter composed of Lactococcus lactis and Leuconostoc citreum. Two strains, L. lactis WiKim0098 and Leu. citreum WiKim0096, showed high antimicrobial activity and mannitol productivity, respectively. These lactic acid bacteria (LAB) were introduced as a starter into kimchi following cultivation in foodgrade liquid medium. Two kimchi samples, with and without starter, were fermented for 12 days at 10°C. Compared to the control kimchi without starter, a lower initial pH and higher number of LAB were observed in kimchi with starter at 0 day. However, the starter in kimchi prolonged the period taken by kimchi to reach to pH 4.2 by approximately 1.5-fold compared to that in the control kimchi. To estimate the effect of the starter on the flavor of kimchi, metabolite changes were evaluated by gas chromatography/mass spectrometry. In starter fermented kimchi, the levels of mannitol and amino acid, which are associated with the flavor of kimchi, were increased following fermentation. The amount of mannitol was confirmed by high-performance liquid chromatography analysis, showing concentrations of 3.4 and 5.1 mg/ml for the control and starter fermented kimchi, respectively. Thus, mixed starter inoculated with L. lactis WiKim0098 and Leu. citreum WiKim0096 may extend the shelf-life of kimchi and improve its sensory characteristics.