一种毛霉表面成熟干酪的蛋白质水解作用评价

从毛豆腐中分离出一株毛霉，并应用于表面成熟干酪，以研究干酪成熟过程中所发生的蛋白质水解作用。在90d 的成熟过程中，干酪的pH 值增加；蛋白质水解作用的评价指标，如干酪外层的水溶性氮- 总氮比、pH4.6水溶性氮- 总氮比、12g/100mL 三氯乙酸可溶性氮- 总氮比，在成熟90d 后分别增加至(23.68 ± 1.07)%、(19.38 ± 1.32)%和(8.61 ± 0.85)%，并且高于干酪的内部相应指标。SDS-PAGE 和毛细管电泳分析干酪的pH4.6 不溶性组分，结果表明酪蛋白在干酪成熟过程中被降解。对干酪成熟过程中分离出的水溶性组分进行RP-HPLC 分析，结果显示成熟过程中蛋白质被水解以及形成一些新肽分子。

Evaluation on the Proteolysis of a Surface Mucor-ripened Cheese during Ripening

A strain of Mucor was isolated from mao-tofu originated from in China and smeared on the surface of fresh cheese. The proteolysis occurring during cheese ripening was studied. The pH of the cheese was increased during 90 d ripening. The indexes of proteolysis, such as ratios of water-soluble nitrogen (WSN) fraction, pH 4.6-soluble nitrogen (pH 4.6-SN) fraction and 12 g/100 mL trichloroacetic acid-soluble nitrogen (12 g/100 mL TCA-SN) fraction to total nitrogen in the external zone of cheese, were elevated to be (23.68±1.07)%, (19.38±1.32)% and (8.61±0.85)%, respectively after 90 d of ripening, slightly higher than those in the central zone. SDS-PAGE and capillary electrophoresis were employed to analyze the pH 4.6-insoluble nitrogen (pH4.6-ISN) fraction of cheese and it was found that casein was degraded during ripening. Peptide profiles of the water-soluble nitrogen fraction separated from cheese were analyzed by reverse phase-high performance liquid chromatography (RP-HPLC) and the results also indicated that the proteolysis occurred and some new peptides were produced.