FURTHER-STUDIES ON LIPID-COMPOSITION OF BOVINE-MILK IN RELATION TO SPONTANEOUS OXIDIZED FLAVOR

Milk samples from five commercial dairy herds having severe problems w ith spontaneous oxidised flavour (SOF) and milk samples from five herd s without such problems were analysed for parameters connected with SO F in milk. The study was directed towards analysing parameters which p rimarily are influenced by feeding. The fatty acid compositions of bot h neutral lipids and phospholipids were determined as well as the conc entrations of alpha-tocopherol beta-carotene and copper in the milk. T he samples were also analysed by dynamic headspace GC to determine vol atile oxidation products. The results showed that the reasons for the occurrence of SOF in a specific herd are still obscure, since the only consistent result found for the five control herds, when compared wit h the corresponding experimental herd, was a higher proportion of the 18:1 trans fatty acid. However, within the affected herds, the differe nce between cows giving milk with off-flavour and cows giving milk wit hout off-flavour was quite clear. In four out of five herds the ratio between antioxidants and fatty acid unsaturation was lower in milk wit h off-flavour, and in the fifth herd an extremely high proportion of 1 8:2 in the phospholipids seemed to have been the reason for the off-fl avour that developed. One of the herds also had a higher copper conten t in milk showing SOF. The data showed differences in importance of al pha-tocopherol and beta-carotene, in different herds. Also the unsatur ation in fatty acids of both neutral lipids and phospholipids had diff erent importance for the flavour stability in different herds. (C) 199 8 SCI.