Department of Food Science, University of Bologna, Piazza Goidanich 60, 47521 Cesena, FC, Italy.
Magn Reson Chem. 2011 Dec;49 Suppl 1:S61-70. doi: 10.1002/mrc.2847.
The content of essential amino acids is an important aspect for determining the nutritional value of food proteins, but their digestibility is also a key property, deeply affected by food processing. The production of Parmigiano Reggiano cheese is closely related to the nutritional quality of the final product; in particular the high digestibility of its proteins is claimed to be proportional to cheese aging. Two different kinds of Parmigiano Reggiano, young (aged 15 months) and old (aged 30 months), were separately digested using an in vitro system that simulates digestive processes in the mouth, stomach and small intestine. Samples were collected at different stages of digestion and the process of protein hydrolysis was explored and compared by low-field (LF) and high-resolution (HR) NMR, together with other biochemical methods. HR-NMR allowed to simultaneously observe the quantity of free amino acids, peptides and proteins, also giving for these latter qualitative information about their dimension. LF-NMR, instead, gave the possibility to observe digestion with no treatments whatsoever, thus representing a technique suitable for on-line measurements. The results pointed out that cheeses with different aging times, although starting from distinct initial compositions, conclude digestion in a similar way, in terms of free amino acids and small organic compounds, but evolve with different kinetics of hydrolysis and peptide formation, discriminating the young from the old cheese.
必需氨基酸的含量是决定食物蛋白质营养价值的一个重要方面，但它们的消化率也是一个关键特性，深受食物加工的影响。帕尔玛奶酪的生产与最终产品的营养质量密切相关；特别是，据说其蛋白质的高消化率与奶酪的陈化成正比。使用体外模拟口腔、胃和小肠消化过程的系统，分别消化两种不同的帕尔玛奶酪，一种是年轻的（15 个月龄），另一种是老的（30 个月龄）。在不同的消化阶段收集样本，并通过低场（LF）和高分辨率（HR）NMR 以及其他生化方法探索和比较蛋白质水解过程。HR-NMR 允许同时观察游离氨基酸、肽和蛋白质的数量，并为这些蛋白质提供有关其尺寸的定性信息。LF-NMR 则可以在不进行任何处理的情况下进行消化观察，因此是一种适合在线测量的技术。结果表明，尽管起始组成不同，但具有不同陈化时间的奶酪在消化方面以相似的方式结束，就游离氨基酸和小分子化合物而言，但在水解和肽形成的动力学方面却以不同的方式发展，从而将年轻奶酪和老奶酪区分开来。
