Changes in the pool of free fatty acids in ovine, bovine and caprine milk fats, effected by viable cells and cell-free extracts of Lactococcus lactis and Debaryomyces vanrijiae

Lipolysis catalysed by lipases, native or released by natural microflora in milk, plays a key role in development of aroma and flavour throughout cheese ripening. This research effort was aimed at a deeper understanding of the action of two wild strains used in traditional ewe's milk cheesemaking in Portugal, viz. Lactococcus lactis and Debaryomyces vanrijiae. They were both tested as viable cells and cell-free extracts - using bovine, ovine and caprine milk fat emulsions as model substrates. Hydrolysis reactions were carried out at 30 and 37 °C, in the case of L. lactis and D. vanrijiae, respectively; the contents of short- and medium-chain fatty acids were determined by high pressure liquid chromatography. Our experimental results showed general trends, viz. preferential depletion of medium chain fatty acids throughout the whole reaction time. However, distinct patterns were observed towards different substrates, depending on the source and form of the biocatalyst at stake.