Abstract: Milk samples from organic and conventionally raised cows differ in the content of specific fatty acids due to the different feed used. Several marker fatty acids (phytanic acid, alpha-linolenic acid (18:3n-3), eicosapentaenoic acid (20:5n-3)) have been proposed to distinguish both types of dairy agriculture. Owing to the higher amount of grass in the feed of organic cows, the concentrations of these fatty acids are usually higher than in conventional milk. In this study, we were interested to determine the day-to-day fluctuation of these and further fatty acids in milk of cows. For this purpose, milk samples from an organic and a conventionally raised cow taken on subsequent days were analyzed for potential marker fatty acids for the authentication of organic milk. An organic cow was milked daily in the morning over a period of 30 days while milk of a conventional cow was collected for 15 days in the morning and evening. Based on milk lipids, no differences were found between morning and evening milk. However, the concentrations of phytanic acid, alpha-linolenic acid (18: 3n-3), eicosapentaenoic acid (20: 5n-3) were similar to twofold higher in organic milk fat than in conventional samples. The day-to-day fluctuations were small, and the lowest value in organic milk was generally higher than the highest value in conventional milk. Phytanic acid is interesting as it will not be influenced by supplementation of n-3 fatty acids in the fodder of conventional cows. Pristanic acid was also similar to 40% higher in organic milk fat, but five conventional samples reached the lowest value in organic milk. Significantly higher concentrations in organic milk fat were also observed for 12-methyltridecanoic acid (i14:0) and 16-methylheptadecanoic acid (i18:0) as well as for vaccenic acid (18:1n-7tr).
Reference: Schroder, M., Yousefi, F., Vetter, W. (2011). Investigating the day-to-day variations of potential marker fatty acids for organic milk in milk from conventionally and organically raised cows. European Food Research and Technology 232(1): 167-174. Available online at: http://dx.doi.org/10.1007/s00217-010-1374-8