Unité d'Ecophysiologie Animale, Production Animale et Modélisation Mathématique, Faculté des Sciences de Sfax,Dépt. des Sciences de la Vie, BP 1171, 3000 Sfax, Tunisia.
J Food Sci. 2013 Sep;78(9):M1405-11. doi: 10.1111/1750-3841.12188. Epub 2013 Aug 5.
The objective of the article was to analyze the influence of psychrotrophic bacteria counts (PBCs) and somatic cell counts (SCCs) on the extent of lipolysis in bulk samples of cow's milk at reception and during cold storage. Samples of milk were analyzed on the day of sampling and subsequently during cold storage. The acidity, fat, density, chloride content, electrical conductivity (EC), bulk milk SCCs (BMSCC), and PBC values were analyzed on the day of sampling and the levels of acidity, EC, SCC, and PBC were analyzed during cold storage at 4 °C for 72 h. The SCC value 869 × 10(3) mL(-1) was higher than the recommended threshold. Lipolysis level at sampling day was related more closely with SCC than with PBC. There was no significant correlation between milk acidity and PBC among others parameters, while the milk mean density was only significant (P < 0.01) correlated with the fat content. The EC and chloride content were consistently correlated (P < 0.001) with BMSCC that allowed them to be used as indicators of mammary gland infection. The milk acidity, EC, PBC, and lipolysis levels increased in relation to the storage time at 4 °C. The lipolysis level during storage was in closer relation to the SCC, but not relation to the PBC. Effects of SCC and PBC on lipolysis decreased throughout the chilling period. It was concluded that initial lipolysis level and intrinsic milk lipoprotein lipase appear more effective than SCC and PBC on the development of lipolysis during storage.
本文旨在分析冷贮过程中嗜冷菌计数（PBC）和体细胞计数（SCC）对牛奶批量样品脂肪分解程度的影响。采集的牛奶样品在采集当天和随后的冷藏过程中进行分析。在采集当天分析酸度、脂肪、密度、氯含量、电导率（EC）、牛奶体细胞计数（BMSCC）和 PBC 值，并在 4°C 冷藏 72 h 期间分析酸度、EC、SCC 和 PBC 值。SCC 值 869×10(3)mL(-1)高于推荐阈值。与 PBC 相比，采样日的脂肪分解水平与 SCC 的相关性更高。除 SCC 外，其他参数之间与酸度之间无显著相关性，而平均密度仅与脂肪含量显著相关（P < 0.01）。EC 和氯含量与 BMSCC 呈一致相关（P < 0.001），可以作为乳腺炎感染的指标。牛奶酸度、EC、PBC 和脂肪分解水平随 4°C 贮藏时间的延长而增加。在贮藏过程中，脂肪分解水平与 SCC 的关系更为密切，但与 PBC 无关。SCC 和 PBC 对脂肪分解的影响在冷却过程中逐渐减弱。综上所述，初始脂肪分解水平和乳内脂蛋白脂肪酶比 SCC 和 PBC 对储存期间脂肪分解的发展更有效。
