Distribution and Content of Geometric Isomers of Conjugated Linoleic Acid in Dairy Foods from the Quebec Province of Canada

The distributions and content of geometrical isomers of conjugated linoleic acids (CLA) in dairy foods such as milk, yogurt, and cheese, produced or being sold in the Quebec province of Canada, were investigated by gas chromatographic analysis. The mean contents of total CLA (mg/g fat) were $5.06{\pm}0.74$ in 4 low-fat milk samples, $14.14{\pm}4.95$ in 6 yogurt samples, and $18.22{\pm}7.89$ in 5 natural ripened cheeses. Among the yogurt samples, YY contained the highest content of total CLA ($20.68{\pm}5.17\;mg/g$ fat). Among the cheese samples, Gruyere contained the highest amount of total CLA ($29.86{\pm}0.62$) as well as c-9,t-11 ($22.03{\pm}0.36\;mg/g$ fat), followed by Jarlsberg ($22.76{\pm}0.14$), Provolone ($16.42{\pm}0.52$), Cheddar ($13.83{\pm}0.81$), and Swiss ($8.23{\pm}1.11$). Based on the distribution ratios of CLA isomers in these dairy foods, the c-9,t-11 isomer appeared to be the major CLA isomer in both the low-fat milk ($89.87{\pm}2.39%$) and yogurt ($90.98{\pm}4.42%$). In the cheeses, however, the ratio of c-9,t-11 ($54.86{\pm}13.06%$) was slightly higher than that of c-10,c-12 ($40.81{\pm}13.40%$).