School of Food and Nutritional Sciences, University College Cork, Cork, Ireland.
J Dairy Res. 2012 May;79(2):176-84. doi: 10.1017/S0022029912000027. Epub 2012 Feb 27.
Milk for cheese production in Ireland is predominantly produced by pasture-fed spring-calving herds. Consequently, there are marked seasonal changes in milk composition, which arise from the interactive lactational, dietary and environmental factors. In this study, Cheddar cheese was manufactured on a laboratory scale from milk taken from a spring calving herd, over a 9-month lactation cycle between early April and early December. Plasmin activity of 6-months-old Cheddar cheese samples generally decreased over ripening time. One-dimensional urea-polyacrylamide gel electrophoresis (PAGE) of cheese samples taken after 6 months of ripening showed an extensive hydrolysis of caseins, with the fastest hydrolysis of α(s1)-caseins in cheeses made in August. A proteomic comparison between cheeses produced from milk taken in April, August and December showed a reduction in levels of β-casein and appearance of additional products, corresponding to low molecular weight hydrolysis products of the caseins. This study has demonstrated that a seasonal milk supply causes compositional differences in Cheddar cheese, and that proteomic tools are helpful in understanding the impact of those differences.
爱尔兰用于奶酪生产的牛奶主要由放牧的春季产犊牛群生产。因此，牛奶成分存在明显的季节性变化，这是由哺乳期、饮食和环境因素的相互作用引起的。在这项研究中，从 4 月初至 12 月初为期 9 个月的哺乳期，从春季产犊牛群采集的牛奶在实验室规模上生产切达奶酪。6 个月龄切达奶酪样品的纤溶酶活性通常随着成熟时间的延长而降低。经过 6 个月成熟后采集的奶酪样品的一维尿素-聚丙烯酰胺凝胶电泳 (PAGE) 显示出对酪蛋白的广泛水解，其中 8 月生产的奶酪中 α(s1)-酪蛋白水解最快。对 4 月、8 月和 12 月采集的牛奶生产的奶酪进行蛋白质组比较显示，β-酪蛋白水平降低，并出现了其他产物，对应于酪蛋白的低分子量水解产物。本研究表明，季节性牛奶供应会导致切达奶酪的成分差异，而蛋白质组学工具有助于了解这些差异的影响。
