INRA, UR1213 Herbivores, F-63122 Saint Genès Champanelle, France.
J Dairy Sci. 2010 Jul;93(7):2846-56. doi: 10.3168/jds.2009-2939.
The aim of this work was to characterize UV-absorbing compounds (UAC) in milk in relation to diet. In winter, 4 groups of cows each received a different diet: concentrate rich containing 35% cocksfoot hay (CCH), maize silage (MS), rye grass silage (RS), or rye grass hay (RH). In summer, 2 additional diets were given: mountain grassland hay (GH) and mountain grassland pasture (GP). Polyphenols were analyzed by HPLC and Folin reaction on forages and UAC were extracted from milks and analyzed by HPLC. In forages, the number of polyphenols was lowest in MS (57) and greatest in GP (85). Twenty-four peaks were identified, accounting for 28 to 47% peak area at 280 nm. Caffeoyl compounds and flavonoid glycosides were mainly found in RH, GH, and GP. Hydrolyzed compounds such as hydroxycinnamic acids and aglycones were found in MS and RS. Estimated amounts of polyphenols were lowest for MS (3.7 g/kg), roughly similar for CH, RS, and RH (about 15 g/kg), and greatest for GH and GP (21.6 and 35.3 g/kg, respectively). About 230 different peaks were separated in milks. Milks from RH and GP contained the lowest (87) and the greatest (127) numbers of peaks, respectively. Only 10 peaks were identified, accounting for 21 to 54% of the total spectra area. In addition to the major compound hippuric acid, phenylacetic acid, benzoic acid, 4-hydroxybenzoic acid benzaldehyde, catechol, and small amounts of ferulic acid were found in varying amounts depending on the diet. Flavonoids such as quercetin, luteolin, and apigenin were also present. Hippuric acid was clearly related to the presence of caffeoylquinic compounds in forages. Other identified UAC may originate essentially from forage simple polyphenols or from cell wall aromatics. Some of the several unknown compounds may also originate from the transformation of other nutrients. Estimated amounts of UAC were widely variable within each animal group. They were surprisingly high in CCH and roughly similar in all milks from preserved forages (about 3.6 mg/L), with generally greater values for GH milks, whereas the greatest amount was found in GP milks (13.3 mg/L). Hierarchical clustering clearly discriminated the 6 diets, showing that there were major differences in GP milks. Some UAC were specific to one or a group of diets. Ultraviolet-absorbing compounds are therefore a potential tool to distinguish between milks according to diet. In addition, they may have a bioactive effect on milk component conservation or on human health.
本研究旨在探讨牛奶中与饮食相关的紫外吸收化合物（UAC）的特征。冬季，将 4 组奶牛分别给予不同的日粮：富含 35%雀麦干草的浓缩饲料（CCH）、玉米青贮（MS）、黑麦草青贮（RS）或黑麦草干草（RH）。在夏季，还提供了另外两种日粮：山地草地干草（GH）和山地草地放牧（GP）。采用高效液相色谱法（HPLC）和福林反应对饲料中的多酚进行分析，采用 HPLC 从牛奶中提取 UAC 并进行分析。在饲料中，MS 中的多酚数量最低（57），GP 中的多酚数量最高（85）。共鉴定出 24 个峰，占 280nm 处峰面积的 28%至 47%。咖啡酰化合物和类黄酮糖苷主要存在于 RH、GH 和 GP 中。在 MS 和 RS 中发现了水解化合物，如羟基肉桂酸和苷元。估计 MS 中的多酚含量最低（3.7g/kg），CH、RS 和 RH 大致相似（约 15g/kg），GH 和 GP 最高（分别为 21.6 和 35.3g/kg）。牛奶中共分离出约 230 个不同的峰。RH 和 GP 牛奶中的峰数最少（87）和最多（127）。仅鉴定出 10 个峰，占总光谱面积的 21%至 54%。除了主要化合物马尿酸外，还根据饮食情况发现了苯乙酸、苯甲酸、对羟基苯甲酸、苯甲醛、儿茶酚和少量阿魏酸。还存在黄酮类化合物，如槲皮素、木樨草素和芹菜素。马尿酸与饲料中咖啡酰奎宁酸化合物的存在明显相关。其他鉴定出的 UAC 可能主要来源于饲料中的简单多酚或细胞壁芳香族化合物。一些未知化合物可能也来源于其他营养素的转化。各动物组内 UAC 的估计量差异很大。在 CCH 中，UAC 的含量出人意料地高，在所有青贮饲料的牛奶中大致相似（约 3.6mg/L），GH 牛奶中的含量一般较高，而 GP 牛奶中的含量最高（13.3mg/L）。层次聚类清楚地区分了 6 种日粮，表明 GP 牛奶之间存在明显差异。一些 UAC 是一种或一组日粮特有的。因此，UAC 是根据饮食区分牛奶的潜在工具。此外，它们可能对牛奶成分的保存或人类健康具有生物活性作用。
