Department of Life and Environmental Sciences, University of Cagliari, via Ospedale 72, 09124 Cagliari, Italy.
Department of Life and Environmental Sciences, University of Cagliari, via Ospedale 72, 09124 Cagliari, Italy; Department of Chemistry, University of Pavia, viale Taramelli 12, 27100 Pavia, Italy.
J Dairy Sci. 2019 Jun;102(6):5005-5018. doi: 10.3168/jds.2018-15885. Epub 2019 Apr 17.
Thermization is a sub-pasteurization heat treatment of cheese milk (at 57-68°C for 15-30 s) aimed to reduce the number of undesirable microbial contaminants with reduced heat damage to the indigenous milk enzymes. In this work, the effects of milk thermization on the compositional parameters, proteolysis indices, free fatty acid levels, and low molecular weight metabolite profiles of ovine cheese were studied. Cheese samples at different ripening stages and produced in 2 different periods of the year were analyzed. While the effects of milk thermization on cheese macro-compositional parameters and free fatty acid levels were not evident due to the predominant effects of milk seasonality and cheese ripening stage, the gas chromatography-mass spectrometry based metabolomics approach of ovine cheese produced from raw and thermized milk highlighted strong differences at the metabolite level. Discriminant analysis applied to gas chromatography-mass spectrometry data provided an excellent classification model where cheese samples were correctly classified as produced from raw or thermized milk. The metabolites that mostly changed due to the thermization process belonged to the classes of free amino acids and saccharides. Gas chromatography-mass spectrometry-based metabolomics has proven to be a valid tool to study the effect of mild heat treatments on the polar metabolite profile in ovine cheese.
热稳定化是奶酪牛奶的亚巴氏杀菌热处理（57-68°C 下 15-30 秒），旨在减少不良微生物污染物的数量，同时减少对本地牛奶酶的热损伤。在这项工作中，研究了牛奶热稳定化对绵羊奶酪组成参数、蛋白水解指数、游离脂肪酸水平和低分子量代谢物谱的影响。分析了不同成熟阶段和在一年中两个不同时期生产的奶酪样品。由于牛奶季节性和奶酪成熟阶段的主要影响，牛奶热稳定化对奶酪宏观组成参数和游离脂肪酸水平的影响不明显，但是基于气相色谱-质谱的绵羊奶酪代谢组学方法突出了在代谢物水平上的强烈差异。判别分析应用于气相色谱-质谱数据提供了一个极好的分类模型，其中奶酪样品被正确地分类为来自生奶或热稳定化奶。由于热稳定化过程而发生最大变化的代谢物属于游离氨基酸和糖的类别。基于气相色谱-质谱的代谢组学已被证明是一种有效的工具，可用于研究温和热处理对绵羊奶酪中极性代谢物谱的影响。
