Population dynamics of lactococci from industrial, artisanal and non-dairyorigins in defined strain starters for Gouda-type cheese

Lactococcal strains from various artisanal and natural niches were studied for the development of defined strain starter (DSS) mesophilic cultures wit h specific flavour forming characteristics as well as with other properties required for Gouda-type cheese. These 'wild' lactococcal strains were foun d to be stable up to 50 subcultivations with regard to their morphology, ge netic profile, bacteriocin production, proteolytic and acidification activi ty, bacteriophage resistance, citrate utilizing ability as well as their ab ility to grow at 4 degreesC and in the presence of 4% NaCl. In addition, th e flavour forming abilities of the strains were found to be stable during s ubcultivation, making them suitable as starter cultures. Different DSS were prepared, each one composed of a limited number of strains for Gouda-type cheese making. These starters included proteolytic, non-proteolytic and cit rate utilising strains, as well as a specific flavour-generating wild strai n. One of the DSS consisted of nisin-producing and nisin-resistant strains. The characteristics of the strains in DSS were studied in milk cultures as well as in cheese making experiments. The population dynamics revealed tha t a number of strains were able to grow well together and thus: were suitab le to be applied in tailor-made starter cultures, whereas other strains cou ld not be maintained during growth in a mixed DSS. The results of populatio n dynamics in the cheese corroborated the results obtained in a milk cultur e. These results may open new avenues for the construction of tailor-made s tarters for new types of cheese. (C) 2001 Elsevier Science Ltd. All rights reserved.