April 14/Beijing/Agriculture Business Week -- According to a study from Beijing, People's Republic of China, "Increasing the content of alpha-linolenic acid in milk fat might be desirable to meet consumer concerns about dietary healthfulness. However, the rich content of polyunsaturated fatty acids (PUFAs) will influence the oxidative stability of milk fat."
"This experiment was carried out to determine the effects of infusion with different amounts of high-linolenic perilla fatty acid (HLPFA) emulsion into the duodenum of dairy cows on milk fatty acid profile and the susceptibility of milk fat to oxidation. In a crossover design, four multiparous Holstein cows were infused duodenally with increasing amounts (0, 40, 80, 120 or 160g/day) of free fatty acids from HLPFA emulsion or with carrier alone. Continuous infusions (20 to 22 hour/day) were for seven days at each amount. Infusions were homogenates of HLPFA with 15g/day of xanthan gum, 5g/day sodium alginate and 25g/day Tween 80; controls received carrier only. The concentration of n-3 PUFAs, especially alpha-linolenic acid, in milk fat increased linearly as HLPFA infusion increased, but the saturated fatty acids decreased linearly. The milk production and the activity of superoxide dismutase, glutathione peroxidase, and catalase in milk tended to decrease quadratically. The milk fat percentage, however, tended to increase. The concentration of malondialdehyde increased quadratically in milk fat," wrote Q.S. Liu and colleagues, Chinese Academy of Agriculture Science.
The researchers concluded, "Suggest that infusion with HLPFA emulsion at varying amounts enhanced the content of n-3 PUFAs in milk fat over the length of experiment but decreased the oxidative stability of milk fat."
Liu and colleagues published the results of their research in the Journal of Agricultural and Food Chemistry ("Influence of Linolenic Acid Content on the Oxidation of Milk Fat." Journal of Agricultural and Food Chemistry, 2010;58(6):3741-3746).
For additional information, contact J.Q. Wang, Chinese Academy Agr Sci, Inst Anim Sci, State Key Lab Anim Nutr, Beijing 100193, People's Republic of China.
From the April 26, 2010, Prepared Foods E-dition