The trans fatty acids content in milk represents
about 2% of total fatty acids, which can be increased to 4–10% of total fatty acids by enhancing dietary unsaturated oils content in the cow’s diet. Trans-vaccenic acid, known as (E)-11-octadecenoic acid (C18:1 trans-11, or TVA), is the main trans fatty acid isomer found in the fat of ruminants and in dairy products, such as milk and yogurts ( Santora, Palmquist, & Roehrig, 2000). It participates in CLA production, through enzymatic action of Δ-9-desaturase find more in mammary glands ( Gnädig et al., 2003), and contributes to the supply of human body CLA ( Butler et al., 2011). It is also an intermediate fatty acid of the CLA biohydrogenation pathway ( Bergamo, Fedeli, Iannibelli, & Marzillo, 2003). Finally, α-linolenic acid (ALA), the major omega-3 fatty acid in milk, has been related to an ability to exert anti-arrhythmic effects in the heart, a positive impact on neurological function (by limiting
central nervous system injury) and protection SKI-606 ic50 against coronary heart disease ( Barceló-Coblijn & Murphy, 2009). It is also the dietary precursor for three long-chain omega-3 polyunsaturated fatty acids (LC-PUFA) synthesis: eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA) ( Brenna, Salem, Sinclair, & Cunnane, 2009). Production of fermented milks, using bifidobacteria, is a big challenge in the dairy industry because milk, on the whole, is not a suitable matrix for the growth
of lactic and probiotic bacteria since they lack essential proteolytic activity (Oliveira, Sodini, Remeuf, & Corrieu, 2001). Interest in bifidobacteria for human health is related to their survival through the intestinal tract and to their role in stimulating the immune system and prevention of microbial gastroenteritis (Foligne et al., 2007 and Hols et al., 2005). In addition, CLA production by bifidobacteria was shown to be a possible mechanism for their health-enhancing properties (Oh et al., 2003). Until now, few studies have explored the effect of organic milk on the growth of bifidobacteria and Prostatic acid phosphatase yogurt starters. To our knowledge, only the work of Florence et al. (2009) describes the acidification profile, fatty acids contents, and chemical composition of organic and conventional milks fermented by bifidobacteria in co-culture with Streptococcus thermophilus. These authors detected higher protein and iron concentrations in organic fermented milks, although no difference was observed in the initial milk. In addition, they found higher relative concentrations of TVA and CLA in organic fermented milks. From this information, it seems that a better knowledge about acidification kinetics and milk composition of organic and conventional fermented milk products is needed. In this context, this study aimed at characterising the behaviour of bifidobacteria and yogurt starters during organic and conventional milk fermentation.