Compositional analysis of dairy fats, phospholipids and positional distribution on TAG from cows fed fish meal
DHA enriched milk fat samples obtained at the University of Guelph from cows fed fish meal (FM) were characterized and compared with milk from cows fed corn/soy silage. The total FA was analyzed by GC equipped with 100m CP Sill 88 capillary column by which more than 100 FA were identified. Ag +-TLC combined with GC was used to analyze all possible positional cis and trans monoenes. GC and Ag+-HPLC was used to resolve all CLA isomers. 9c11t, 18:2 was the major CLA isomer found in both diets. The other major CLA isomers were 9t11c and 7t9c; the former was identified by GC, and the latter by Ag+-HPLC.;The TAG and PL were separated using Supelco LC-Sil columns. PL were analyzed and distributed into three major classes: PC, PE and SM. SM was the most saturated PL fraction (ca. 70%). There was an increase in the degree of unsaturation of the analyzed PL in the following order PE> PC> SM. The CLA content in the major PL was lower than in TAG.;Positional analysis of TAG was performed enzymaticaly and using Grignard reactions. The MAG were isolated on boric acid impregnated TLC plates and analyzed as their butyl esters by GC, which was confirmed by GC-MS. The distribution of short chain-FA was found in both sn-1,3 and sn -2 positions. For FM samples, C12:0, C16:0 and C18:0 FA were predominantly at sn-1,3 position.;The inclusion of FM into diets of dairy cows resulted in an increase of DHA (0.04 to 0.17%). Increases were also observed for 9c11t-CLA (0.39% to 0.66%), 7t9c-CLA (0.05% to 0.26%), and 9t11c-CLA isomers (0.05 to 0.13%). 10t-18:1 increased (0.57% to 4.58%) and 11t-18:1 decreased (1.16 to 0.96%).