Carpino Stefania, Randazzo Cinzia L, Pino Alessandra, Russo Nunziatina, Rapisarda Teresa, Belvedere Gianni, Caggia Cinzia
CoRFiLaC, Regione Siciliana, 97100 Ragusa, Italy.
Department of Agricultural, Food and Environment, University of Catania, via Santa Sofia 98, 95124 Catania, Italy.
Food Microbiol. 2017 Feb;61:126-135. doi: 10.1016/j.fm.2016.09.006. Epub 2016 Sep 13.
The objectives of the present study were to characterize the biofilm microbiota of 11 different farms (from A to K), producing PDO Ragusano cheese, and to investigate on its ability to generate volatile organic compounds (VOCs) in milk samples inoculated with biofilm and incubated under Ragusano cheese making conditions. The biofilms were subjected to plate counting and PCR/T/DGGE analysis and the VOCs generated in incubated milk samples were evaluated through SmartNose, GC/O, and GC/MS. Streptococcus thermophilus was the dominant species both in biofilms and in incubated milks. Lactobacillus, Lactococcus, Enterococcus and Leuconostoc were also identified. Low levels of Pseudomonas spp. and yeasts counts were detected, whereas coliforms, Listeria monocytogenes and Salmonella spp., were never found. SmartNose and GC/O analyses were able to differentiate incubated milk samples on the basis of the odour compounds, highlighting that samples E and F overlapped and sample C was clearly separated from the others. These results complied with those acquired by GC/MS analysis, that detected in total 20 VOCs. Principal component analysis showed positive correlations (r > 0.6; P < 0.05) between some lactic acid bacteria (LAB) and VOCs: such as Enterococcus hirae with alcohols, Lactococcus lactis, Lactobacillus plantarum, Lactobacillus casei and Lactobacillus delbrueckii with aldehydes, and Lactobacillus fermentum, Lactobacillus helveticus and Lactobacillus hilgardii with ketones. This work demonstrates that biofilm represents an excellent source of LAB biodiversity, which contribute to generate VOCs during the production of PDO Ragusano cheese.
本研究的目的是对11个不同农场（从A到K）生产受保护的原产地名称（PDO）拉古萨诺奶酪的生物膜微生物群进行特征分析，并研究其在接种生物膜并在拉古萨诺奶酪制作条件下孵育的牛奶样品中产生挥发性有机化合物（VOCs）的能力。对生物膜进行平板计数和PCR/T/变性梯度凝胶电泳（DGGE）分析，并通过智能鼻（SmartNose）、气相色谱-嗅闻联用仪（GC/O）和气相色谱-质谱联用仪（GC/MS）对孵育牛奶样品中产生的VOCs进行评估。嗜热链球菌是生物膜和孵育牛奶中的优势菌种。还鉴定出了乳杆菌属、乳球菌属、肠球菌属和明串珠菌属。检测到少量假单胞菌属和酵母菌，而从未发现大肠菌群、单核细胞增生李斯特菌和沙门氏菌属。智能鼻和GC/O分析能够根据气味化合物区分孵育的牛奶样品，突出显示样品E和F重叠，样品C与其他样品明显分离。这些结果与GC/MS分析获得的结果一致，GC/MS分析总共检测到20种VOCs。主成分分析显示一些乳酸菌（LAB）与VOCs之间存在正相关（r>0.6；P<0.05）：例如，平肠球菌与醇类、乳酸乳球菌、植物乳杆菌、干酪乳杆菌和德氏乳杆菌与醛类，以及发酵乳杆菌、瑞士乳杆菌和希氏乳杆菌与酮类。这项工作表明，生物膜是LAB生物多样性的一个极好来源，在PDO拉古萨诺奶酪生产过程中有助于产生VOCs。
