It is interesting to maintain a high relative content of trans-C18:1 as it participates in CLA production in the human ( Butler et al., 2011 and Gnädig et al., 2003) and acts as an intermediate fatty acid in the biohydrogenation pathway ( Bergamo et al., 2003). During storage of the fermented products, the trans-C18:1 concentration remained stable,

whatever the kind of milk and starters used. Finally, after 7 days storage at 4 °C, it was higher in organic fermented milks (3.3 ± 0.03%) than in conventional milks (2.2 ± 0.03%). During fermentation, CLA relative content significantly increased (P < 0.05), at different levels in organic (17%) and conventional (12%) milks ( Fig. 1B). This was explained by Ekinci et al. (2008), who indicated that enzymatic reactions occurred in the biohydrogenation pathway, thus increasing CLA level during the production of fermented products. Similar results were reported GSK1120212 purchase by Oliveira et GSI-IX supplier al. (2009) in fermented milks, whereas no change was observed in probiotic fermented products made with conventional milk, as reported by Van de Guchte et al. (2006). As these authors used different strains, this behaviour was thus strain-dependent. The difference between conventional and organic fermented milks found in our study was considered as significant (P < 0.05).

The CLA relative concentration was higher in organic fermented milks (1.2 ± 0.01%) than in conventional fermented milks (0.8 ± 0.01%) ( Fig. 1B), in accord with previous results ( Oliveira et al., 2009). This higher CLA relative content in organic fermented products was the result of both initial CLA percentage in milk and changes

during fermentation. In addition to these results, CLA relative concentration did not significantly vary in fermented milks according to the co-cultures. This result indicates that 4��8C B. lactis HN019 had no effect on CLA relative content, and that the variations observed during fermentation could be ascribed to S. thermophilus or L. bulgaricus, as suggested by Lin (2003). Finally, the CLA percentage slightly decreased during cold storage of three of the fermented milks (P < 0.05), that may be related to the activation of reduction steps in the biohydrogenation pathway ( Kim & Liu, 2002). However, by considering the conventional fermented milk with yogurt starters and bifidobacteria, a significant increase of relative CLA content was observed. Fig. 1C shows that, during fermentation, ALA level did not vary significantly in organic milk (0.5 ± 0.02%), for the two kinds of culture. In contrast, a significant decrease (P < 0.05) was noted during fermentation and storage of conventional milk products (from 0.38 ± 0.02% to 0.30 ± 0.02%). These results are not in agreement with those of Van de Guchte et al.