Nafferton Ecological Farming Group, School of Agriculture, Food and Rural Development, Newcastle University, Nafferton Farm, Stocksfield, Northumberland, NE43 7XD, United Kingdom.
J Dairy Sci. 2011 Jan;94(1):24-36. doi: 10.3168/jds.2010-3331.
This study of UK retail milk identified highly significant variations in fat composition. The survey, conducted over 2 yr replicating summer and winter, sampled 22 brands, 10 of which indicated organic production systems. Results corroborate earlier farm-based findings considering fat composition of milk produced under conventional and organic management. Organic milk had higher concentrations of beneficial fatty acids (FA) than conventional milk, including total polyunsaturated fatty acids (PUFA; 39.4 vs. 31.8 g/kg of total FA), conjugated linoleic acid cis-9,trans-11 (CLA9; 7.4 v 5.6 g/kg of FA), and α-linolenic acid (α-LN; 6.9 vs. 4.4 g/kg of FA). As expected, purchase season had a strong effect on fat composition: compared with milk purchased in winter, summer milk had a lower concentration of saturated fatty acids (682 vs. 725 g/kg of FA) and higher concentrations of PUFA (37.6 vs. 32.8 g/kg of FA), CLA9 (8.1 vs. 4.7 g/kg of FA), and α-LN (6.5 vs. 4.6 g/kg of FA). Differences identified between sampling years were more surprising: compared with that in yr 2, milk purchased in year 1 had higher concentrations of PUFA (37.5 vs. 32.9 g/kg of FA), α-LN (6.0 vs. 5.1 g/kg of FA), and linoleic acid (19.9 vs. 17.5 g/kg of FA) and lower concentrations of C16:0 and C14:0 (332 vs. 357 and 110 vs. 118 g/kg of FA, respectively). Strong interactions were identified between management and season as well as between season and year of the study. As in the earlier farm studies, differences in fat composition between systems were greater for summer compared with winter milk. Large between-year differences may be due to changes in weather influencing milk composition through forage availability, quality, and intake. If climate change predictions materialize, both forage and dairy management may have to adapt to maintain current milk quality. Considerable variation existed in milk fat composition between brands.
本研究对英国零售牛奶的脂肪成分进行了深入分析，结果发现其中存在显著差异。该研究在为期 2 年的时间里进行了两次采样，共采集了 22 个品牌的牛奶，其中 10 个品牌的牛奶表明采用了有机生产体系。研究结果与早期基于农场的研究结果一致，都表明在传统和有机管理下生产的牛奶的脂肪成分存在差异。与传统牛奶相比，有机牛奶中含有更多有益脂肪酸（FA），包括总多不饱和脂肪酸（PUFA；39.4 比 31.8g/kg 总 FA）、共轭亚油酸顺式 9，反式 11（CLA9；7.4 比 5.6g/kg FA）和α-亚麻酸（α-LN；6.9 比 4.4g/kg FA）。正如预期的那样，购买季节对脂肪成分有很强的影响：与冬季购买的牛奶相比，夏季牛奶的饱和脂肪酸含量较低（682 比 725g/kg FA），多不饱和脂肪酸（37.6 比 32.8g/kg FA）、CLA9（8.1 比 4.7g/kg FA）和α-LN（6.5 比 4.6g/kg FA）含量较高。与采样年份相比，发现的差异更为令人惊讶：与 2 年相比，1 年购买的牛奶中多不饱和脂肪酸（37.5 比 32.9g/kg FA）、α-LN（6.0 比 5.1g/kg FA）和亚油酸（19.9 比 17.5g/kg FA）含量较高，而 C16:0 和 C14:0 含量较低（332 比 357 和 110 比 118g/kg FA）。管理和季节之间以及季节和研究年份之间都存在很强的相互作用。与早期的农场研究一样，与冬季牛奶相比，夏季牛奶在系统间的脂肪成分差异更大。由于天气变化通过饲料供应、质量和摄入量影响牛奶成分，因此年际间的巨大差异可能是由于天气变化引起的。如果气候变化预测成为现实，无论是饲料还是奶制品管理都需要适应，以保持当前的牛奶质量。不同品牌的牛奶脂肪成分存在相当大的差异。
