Institute of Sciences of Food Production, National Research Council of Italy, Via G. Amendola 122/o, 70126 Bari, Italy.
Food Microbiol. 2012 May;30(1):37-44. doi: 10.1016/j.fm.2011.10.009. Epub 2011 Oct 14.
The aim of this study was to analyse non-lactic acid bacteria populations (NLABPs) and evaluate their role in proteolysis of cold-stored high moisture (HM) Mozzarella cheese. NLABPs reached values close to 8 log cfu mL⁻¹ after seven days of cold storage. Sequencing of 16 rDNA and rpoB genes and molecular biotyping allowed to identify 66 bacterial strains belonging to 25 species from 15 genera, mainly represented by Pseudomonas, Acinetobacter, and Rahnella. Fifteen strains showed proteolytic activity values higher than 1000.00 μg Gly mL⁻¹ after 24 h of growth in skimmed milk. Moreover, as shown by Urea-PAGE, 11 proteolytic strains caused partial or total disappearance of at least one of the caseins. Their proteolytic behaviour was assessed even when they grew inside the governing liquid together with HM Mozzarella cheese at 4 °C for 12 days. This is the first report that throws light on the complexity of NLABPs in HM Mozzarella cheese, demonstrating that some strains caused the partial hydrolysis of α, β, and γ caseins on its outer surface where a concomitant wrinkling and successive exfoliation became visible without significant changes in texture characteristics.
本研究旨在分析非乳酸菌（NLABPs）种群，并评估其在冷藏高水分（HM）马苏里拉奶酪中蛋白质水解的作用。NLABPs 在冷藏七天后达到接近 8 log cfu mL⁻¹ 的值。16 rDNA 和 rpoB 基因测序和分子生物分型可鉴定出 66 株细菌，它们属于 15 个属的 25 个种，主要代表菌为假单胞菌、不动杆菌和产碱杆菌。15 株细菌在脱脂乳中生长 24 小时后，其蛋白酶活性值高于 1000.00 μg Gly mL⁻¹。此外，如尿素-PAGE 所示，11 株有蛋白酶活性的菌株导致至少一种酪蛋白的部分或完全消失。即使在 4°C 下与 HM 马苏里拉奶酪一起生长 12 天，它们的蛋白酶活性也得到了评估。这是首次报道高水分马苏里拉奶酪中非乳酸菌的复杂性，证明一些菌株会导致其外表面的 α、β 和 γ 酪蛋白部分水解，从而导致可见的表面起皱和随后的剥落，而质地特性没有明显变化。
