Microbial production of conjugated linoleic and linolenic acids in fermented foods: Technological bottlenecks

Several food-grade bacteria are known to produce conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA) from linoleic acid (LA) and α-linolenic acid (ALA), respectively. Therefore, bifidobacteria and a Lactobacillus sakei strain, able to produce CLA and CLNA in vitro, were applied as starter cultures for the fermentation of milk and meat, respectively. However, for both the fermented milk and meat no increase in CLA and CLNA content was obtained. Although LA and ALA were present in sufficient amounts in milk, their availability as free fatty acids was likely too low. During meat fermentation, the prevailing temperature and pH conditions most probably were the limiting factors for conversion of LA and ALA. Practical applications: The market interest in CLA and CLNA has increased because of their potential health-promoting properties. It has been suggested that increased levels of CLA and CLNA isomers in fermented food products might be obtained through the use of appropriate starter cultures. From the present study, it became clear that this approach is not straightforward and more research is needed to investigate the possibility of using selected bacterial strains to increase the levels of CLA and CLNA in fermented foods.