CONTROLLING CABBAGE FERMENTATIONS WITH NISIN AND NISIN-RESISTANT LEUCONOSTOC-MESENTEROIDES

A paired starter culture system for sauerkraut fermentation was proposed previously by our laboratory, consisting of a nisin-producing strain of Lactococcus lactis and a nisin-resistant strain of Leuconostoc mesenteroides. The objectives of this study were to determine nisin production and stability by a genetically marked culture of L. lactis NCK400 in brined cabbage fermentations and to study the effect of purified nisin on the natural microflora in brined cabbage. We found that NCK400 produced up to 700 IU ml-1 of nisin in brined cabbage within 24 h, but by 72 h nisin activity was no longer detectable. The nisin produced was shown to have an effect on the microflora of the fermentation, however, resulting in a 40% reduction in the population of homofermentative lactic acid bacteria (LAB) at 33 days. We also found that the addition of purified nisin to brined cabbage (up to 12 000 IU ml-1) resulted in a reduction in the cell counts of LAB, as compared to a non-treated cabbage brine, to the extent that fermentation by Gram-negative bacteria occurred. The addition of a nisin-resistant L. mesenteroides strain to the nisin-treated cabbage resulted in a heterolactic fermentation by the added culture, with no evidence of a homolactic fermentation for at least 20 days. We concluded that nisin produced in situ or added to brined cabbage can direct the progression of the species in the resultant fermentations, by preventing the growth of naturally present LAB.