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5ummary -L rhamnosus JCL 1211 and L casei JCL 1227 isolated from hard cheese facultatively heterofermentative microflora were shown to negatively interfere with the growth of P freudenreichii in hard Swiss-type cheese. As the observed inhibition cou Id not be reproduced in batch cultures, the metabolism of inhibitory species was studied in cheese and in culture. Citrate appears to be the principal energy source for growth of facultatively heterofermentative microflora which metabolizes it to acetate, formate and carbonate. Small amounts of diacetyl are also produced during citrate fermentation. Diacetyl, acetate and formate can participate in the inhibitory ettect observed. L rhamnosus

A large number of microorganisms, both starter microorganisms and non-starter lactic acid bacteria originating from the base milk, or from various contamination sources during cheese manufacture, is associated with cheese ripening and the formation of flavour, texture and aroma. Under controlled conditions, Emmental and Bergkäse, a Gruyère-type cheese variety, were produced from pasteurised milk with standard starters and defined strains of facultatively heterofermentative lactobacilli (FHL), and partly with addition of a defined mixture of enterococci. Lactobacillus casei subsp. casei and L. rhamnosus (two strains each) were selected with respect to their potential for the utilisation of citric acid and ribose as sole energy source. The FHL developed up to 10(8) cfu/g within the first weeks of ripening, and viable counts in mature cheeses were 10(7) cfu/g, independent of the cheese variety. Bergkäse made with addition of L. rhamnosus strains showed a more pronounced proteolysis, resulting in reduced firmness and elasticity values of the cheese body, and FHL strains able to utilise citric acid improved the appearance of the cheeses by increasing the number of small eyes to the desired level. In Emmental cheese, the citric acid (+) strains reduced the intensity of propionic acid formation as the FHL apparently competed with the propionibacteria, and enterococci disappeared completely during maturation. Although further work is needed the study shows that, depending on the cheese variety, particular properties of FHL adjunct starters significantly affect important quality attributes of the resulting cheeses.