The influence of selected yeast strains (Pichia fermentans, Issatchenkia orientalis, Yarrowia lipolytica) on Camembert-type cheeses has been investigated by monitoring their microbial and compositional changes. During the ripening period from day 1 to day 15, the yeast strains grew exponentially and then slowed to a moderate growth rate. Our results indicated that the selected strains did not significantly affect the general characteristics of cheese but rather the content and ratio of individual free amino acids (P<0.05). In the cheese with added I. orientalis, a greater amount of small peptides and a higher concentration of non-protein nitrogen and NH3 were found. Meanwhile, the presence of adjunct yeasts did not enhance the lipolysis activity in cheese. A principal component analysis of 30 free fatty acids and volatile compounds differentiated five cheeses out of eight according to the content of specific free fatty acids and volatile compounds. In terms of the ripening period, two groups of cheeses at 15 and 45 days were distinguished.

Summary To obtain functional yeast with antioxidant ability for food industry, the antioxidant activity of intact cell and intracellular cell‐free extract of Pichia fermentans BY5 and Issatchenkia orientalis BY10 was investigated. Both intact cell and extract of them demonstrated antioxidant activity ranged from 49% to 68%. The ability to scavenge 1, 1‐diphenyl‐2‐picrylhydrazyl free radicals were 12–41%. Furthermore, the reducing activity, Fe 2+ ‐chelating ability, scavenging of reactive oxygen species of extracts illuminated these two isolates had excellent antioxidant ability. And then, the attenuated effect of cell‐free extracts from these two strains was evaluated using 4‐nitroquiunoline 1‐oxide (4‐NQO) as an inducing reagent. The results indicated that the addition of extraction inhibit the lipid peroxidation induced by 4‐NQO, which mainly caused by the protective intracellular protein rather than the polysaccharides. Therefore, these two yeast strains have potential to be utilised for production of functional foods.