National Agricultural Research Foundation, Dairy Research Institute, Katsikas, Ioannina, Greece.
J Food Prot. 2010 Jul;73(7):1294-303. doi: 10.4315/0362-028x-73.7.1294.
The microflora of four batches of traditional Greek Graviera cheese was studied at 5 weeks of ripening, and 200 lactic acid bacteria (LAB) isolates were phenotypically characterized and screened for antilisterial bacteriocins. The cheeses were also analyzed for organic acids by high-performance liquid chromatography and for the potential presence of 25 known LAB bacteriocin genes directly in cheese and their microbial consortia by PCR. All batches were safe according to the European Union regulatory criteria for Listeria monocytogenes, Salmonella, enterobacteria, and coagulase-positive staphylococci. The cheese flora was dominated by nonstarter Lactobacillus casei/paracasei (67.5%) and Lactobacillus plantarum (16.3%) strains, whereas few Streptococcus thermophilus (3.8%), Lactococcus lactis subsp. lactis (0.6%), and Leuconostoc (1.9%) organisms were present. Enterococcus faecium (9.4%) and Enterococcus durans (0.6%) were isolated among the dominant LAB from two batches; however, enterococci were present in all batches at 10- to 100-fold lower populations than mesophilic lactobacilli. Sixteen E. faecium isolates produced antilisterial enterocins. In accordance, enterocin B gene was detectable in all cheeses and enterocin P gene was present in one cheese, whereas the consortia of all cheeses contained at least two of the enterocin A, B, P, 31, L50A, and L50B genes. Plantaricin A gene was also amplified from all cheeses. Mean concentrations of lactic, acetic, citric, and propionic acids in the ripened cheeses exceeded 1.5% in total, of which approximately 0.9% was lactate. Thus, organic acid contents constitute an important hurdle factor for inhibiting growth of pathogens in traditional Graviera cheese products, with LAB bacteriocins, mainly enterocins, potentially contributing to increased cheese safety.
研究了四个批次的传统希腊 Graviera 奶酪在成熟 5 周时的微生物群，并对 200 株乳酸菌（LAB）分离株进行了表型特征分析，并筛选出具有抗李斯特菌细菌素的分离株。还通过高效液相色谱法分析了奶酪中的有机酸，并通过 PCR 直接在奶酪及其微生物群落中分析了潜在的 25 种已知的 LAB 细菌素基因。所有批次均符合欧盟对单核细胞增生李斯特菌、沙门氏菌、肠杆菌和凝固酶阳性葡萄球菌的监管标准，是安全的。奶酪菌群主要由非发酵乳杆菌/副干酪乳杆菌（67.5%）和植物乳杆菌（16.3%）菌株主导，而很少有嗜热链球菌（3.8%）、乳球菌乳亚种（0.6%）和肠球菌（1.9%）存在。在两个批次中，从优势 LAB 中分离出屎肠球菌（9.4%）和耐久肠球菌（0.6%）；然而，肠球菌在所有批次中的数量均低于嗜温乳杆菌 10-100 倍。16 株屎肠球菌分离株产生抗李斯特菌肠球菌素。因此，在所有奶酪中都可以检测到肠球菌素 B 基因，在一种奶酪中可以检测到肠球菌素 P 基因，而所有奶酪的菌群至少包含肠球菌素 A、B、P、31、L50A 和 L50B 基因中的两种。所有奶酪中也扩增到了素 A 基因。成熟奶酪中总乳酸、乙酸、柠檬酸和丙酸的浓度均超过 1.5%，其中约 0.9%为乳酸。因此，有机酸含量是抑制传统 Graviera 奶酪产品中病原体生长的一个重要障碍因素，而 LAB 细菌素，主要是肠球菌素，可能有助于提高奶酪的安全性。
