Biochemistry and Molecular Biology, Universidad del País Vasco/Euskal Herriko Unibertsitatea, 01006 Vitoria-Gasteiz, Spain.
J Dairy Res. 2012 Nov;79(4):485-94. doi: 10.1017/S0022029912000490. Epub 2012 Sep 24.
The objective of the present work was to study the differences in the fatty acid (FA) composition of raw sheep milk fat under commercial milk production conditions throughout lactation, in two consecutive years. Particular attention was placed on the C18:2cis-9,trans-11 isomer, C18:1trans-11 acid, and unsaturated FA as the feeding regimen of 10 commercial flocks of latxa dairy sheep changed from indoor feeding to part-time grazing conditions (from early spring) as traditionally practiced in the Basque Country (Northern Spain). Farms located at an altitude of between 600 and 700 m, in two different geographical areas with different rainfall were selected. Milk samples were collected monthly from late January (indoor feeding) until mid-, or end of, June (outdoor feeding), during two consecutive years. In spite of some interannual variability (most likely due to large differences in rainfall), the evolution of individual FA throughout lactation was comparable between years, indicating that it was reproducible under commercial milk production conditions. The average concentrations of C18:2cis-9,trans-11 isomer and C18:1trans-11 acid in milk from the commercial flocks increased about 200% during the transition period (end of March or early April until May), from indoor feeding (late January or early February until the end of March) to the outdoor period (early May to mid-June), remaining constant during the outdoor period (27·53 ± 9·32 μmol/g fat and 71·58 ± 20·53 μmol/g fat, respectively). Non-atherogenic FA comprised approximately 50% of all saturated FA at any time during lactation, whereas the milk atherogenicity index decreased significantly during the outdoor period. The Trolox-equivalent antioxidant capacity of the water-soluble milk fraction did not appear to be influenced by feeding management. The FA composition of cheeses made during the second year with milk from the indoor or outdoor periods reflected those of the corresponding milks. A principal components analysis clearly showed that differences in the milk FA composition were primarily due to outdoor grazing, with very little contribution from the geographical zone or the year.
本研究的目的是在连续两年的时间里，研究商业牛奶生产条件下绵羊奶脂肪中脂肪酸（FA）组成的差异。特别关注 C18:2cis-9,trans-11 异构体、C18:1trans-11 酸和不饱和 FA，因为 10 个拉塔莎奶绵羊商业羊群的饲养方案从室内饲养改为半放牧（从早春开始），这是西班牙巴斯克地区的传统做法。选择了海拔在 600 到 700 米之间的农场，位于两个具有不同降雨量的不同地理区域。从 1 月下旬（室内饲养）到 6 月中旬或下旬（室外饲养），每月采集牛奶样品，连续两年。尽管存在一些年际变化（很可能是由于降雨量差异很大），但在整个泌乳期，单个 FA 的演变在两年之间是可比的，表明在商业牛奶生产条件下是可重复的。商业羊群牛奶中 C18:2cis-9,trans-11 异构体和 C18:1trans-11 酸的平均浓度在过渡期间（3 月底或 4 月初至 5 月）增加了约 200%，从室内饲养（1 月下旬或 2 月初至 3 月底）到室外（5 月初至 6 月中旬），在室外期间保持不变（分别为 27.53±9.32μmol/g 脂肪和 71.58±20.53μmol/g 脂肪）。非动脉粥样硬化 FA 在泌乳期的任何时候都约占所有饱和 FA 的 50%，而牛奶致动脉粥样硬化指数在室外期间显著下降。水溶性牛奶部分的 Trolox 等效抗氧化能力似乎不受饲养管理的影响。第二年室内或室外产奶制成的奶酪的 FA 组成反映了相应牛奶的 FA 组成。主成分分析清楚地表明，牛奶 FA 组成的差异主要是由于户外放牧，而地理位置或年份的贡献很小。
