Engel Erwan, Ferlay Anne, Cornu Agnès, Chilliard Yves, Agabriel Claire, Bielicki Guy, Martin Bruno
INRA UR370 Qualité des Produits Animaux, 63122 Saint-Genès-Champanelle, France.
J Agric Food Chem. 2007 Oct 31;55(22):9099-108. doi: 10.1021/jf0714620. Epub 2007 Oct 2.
The first objective of the present paper was to assess the potential of both isotopic ( (18)O/ (16)O in milk water) and molecular biomarkers (terpenes, fatty acids, carotenoids, and vitamins) and milk color to discriminate the production zone (lowland or upland areas) from which 49 tanker bulk milks were collected over one year from a total of 204 farms. The milk water (18)O enrichment was higher in lowland (<500 m altitude) than in upland (>700 m altitude), but the delta (18)O values failed to discriminate systematically the production zone at the scale of the year because of its high variability related to the sampling period. In contrast with vitamins A and E, carotenoids, and milk color measurements, terpenes and fatty acids were confirmed to be relevant tracers of the production zone. The milk compounds with the strongest discriminative potential were fatty acids, which were determined by high-resolution gas chromatography. The calculation of fatty acid ratios, which permits the limitation of using fatty acid relative quantity expressed in percentage of total fatty acids to be overcome, was shown to be particularly relevant in discriminating upland from lowland milk ratios. The selection of two pairs of ratios, namely, iso-C17:0/C18:3 n-3 and iso-C15:0/iso-C14:0, enabled the authentication of 100% of the highland versus lowland milks whatever the season. The second objective was to evaluate the relevance of fatty acid composition to discriminate milks according to the proportion of corn silage in the diets of dairy cows. The selection of two fatty acids ratios, namely, trans11 cis15-C18:2/trans11-C18:1 and cis9-C16:1/iso-C16:0, enabled the correct classification of 100% of the milk samples according to the proportion of corn silage in the basic fodder rations (<25% vs >30%). The relationship between the milk production zone and the type of forage fed to the cows is discussed.
本文的首要目标是评估同位素（乳水中的(18)O/(16)O）和分子生物标志物（萜类、脂肪酸、类胡萝卜素和维生素）以及乳颜色区分生产区域（低地或高地）的潜力，在一年时间里，从总共204个农场收集了49罐散装牛奶，这些牛奶来自不同生产区域。低地（海拔<500米）乳水中的(18)O富集程度高于高地（海拔>700米），但由于与采样期相关的高变异性，δ(18)O值在年度尺度上未能系统地区分生产区域。与维生素A和E、类胡萝卜素以及乳颜色测量结果不同，萜类和脂肪酸被证实是生产区域的相关示踪剂。具有最强区分潜力的乳成分是脂肪酸，通过高分辨率气相色谱法测定。脂肪酸比率的计算克服了使用以总脂肪酸百分比表示的脂肪酸相对量的局限性，在区分高地和低地牛奶比率方面显示出特别的相关性。选择两对比率，即异-C17:0/C18:3 n-3和异-C15:0/异-C14:（此处原文有误，推测为异-C15:0/异-C14:0），无论季节如何，都能100%鉴定高地牛奶与低地牛奶。第二个目标是评估脂肪酸组成根据奶牛日粮中玉米青贮比例区分牛奶的相关性。选择两个脂肪酸比率，即反式11顺式15-C18:2/反式11-C18:1和顺式9-C16:1/异-C16:0，能够根据基础饲料日粮中玉米青贮的比例（<25%与>30%）对100%的牛奶样品进行正确分类。本文还讨论了牛奶生产区域与奶牛所喂饲草料类型之间的关系。
