Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy.
Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy; BIOGEST - SITEIA, University of Modena and Reggio Emilia, Modena, Italy.
Int J Food Microbiol. 2019 Jan 16;289:200-208. doi: 10.1016/j.ijfoodmicro.2018.09.017. Epub 2018 Sep 20.
Fourteen lots of cooked ham in modified atmosphere packaging (CH) were analyzed within a few days from packaging (S) and at the end of the shelf-life (E), after storage at 7 °C to simulate thermal abuse. Five more lots, rejected from the market because spoiled (R), were included in the study. Quality of the products was generally compromised during the shelf life, with only 4 lots remaining unaltered. Analysis of 16S rRNA gene amplicons resulted in 801 OTUs. S samples presented a higher diversity than E and R ones. At the beginning of the shelf life, Proteobacteria and Firmicutes dominated the microbiota, with Acinetobacter, Brochothrix, Carnobacterium, Lactobacillus, Prevotella, Pseudomonas, Psychrobacter, Weissella, Vibrio rumoiensis occurring frequently and/or abundantly. E and R samples were dominated by Firmicutes mostly ascribed to Lactobacillales. It is noteworthy the appearance of abundant Leuconostoc, negligible in S samples, in some E and R samples, while in other LAB were outnumbered by V. rumoiensis or Brochothrix thermosphacta. The microbiota of spoiled and R samples could not be clustered on the basis of specific defects (discoloration, presence of slime, sourness, and swollen packages) or supplemented additives. LAB population of S samples, averaging 2.9 log(cfu/g), increased to 7.7 log(cfu/g) in the E and R samples. Dominant cultivable LAB belonged to the species Lactobacillus sakei and Leuconostoc carnosum. The same biotypes ascribed to different species where often found in the corresponding S and R samples, and sometime in different batches provided from the same producer, suggesting a recurrent contamination from the plant of production. Consistently with growth of LAB, initial pH (6.26) dropped to 5.74 in E samples. Volatiles organic compound (VOCs) analysis revealed that ethanol was the major metabolite produced during the shelf life. The profile of volatile compounds got enriched with other molecules (e.g. 2-butanone, ethyl acetate, acetic acid, acetoin, butanoic acid, ethyl ester, butanoic acid, and 2,3-butanediol) mainly ascribed to microbial metabolism.
将 14 批经过改良气氛包装的熟火腿（CH）在包装后几天内（S）和货架期结束时（E）进行分析，在 7°C 下储存以模拟热滥用。另有 5 批因变质而被市场拒收的产品（R）也包括在研究中。在货架期内，产品质量普遍受损，只有 4 批产品保持不变。16S rRNA 基因扩增子分析产生了 801 个 OTUs。S 样品的多样性高于 E 和 R 样品。在货架期开始时，变形菌门和厚壁菌门主导着微生物群，经常出现和/或大量存在不动杆菌属、布鲁氏菌属、肠球菌属、乳杆菌属、普雷沃氏菌属、假单胞菌属、嗜冷杆菌属、魏斯氏菌属和魏氏梭菌。E 和 R 样品主要由Firmicutes 组成，主要归因于乳杆菌目。值得注意的是，在一些 E 和 R 样品中，大量出现了丰度很高的肠球菌属，而在 S 样品中则很少见，而在其他 LAB 中，肠球菌属则被魏氏梭菌或热死环丝菌所超过。变质和 R 样品的微生物群不能根据特定缺陷（变色、出现粘液、酸味和膨胀包装）或补充添加剂进行聚类。S 样品中 LAB 种群的平均数量为 2.9 log(cfu/g)，在 E 和 R 样品中增加到 7.7 log(cfu/g)。优势可培养 LAB 属于乳杆菌属和肠球菌属。在相应的 S 和 R 样品中经常发现属于不同种的相同生物型，有时在同一生产商提供的不同批次中也能发现，这表明生产工厂存在反复污染。与 LAB 的生长一致，初始 pH 值（6.26）下降到 E 样品中的 5.74。挥发性有机化合物（VOCs）分析表明，乙醇是货架期内主要产生的代谢物。货架期内，挥发性化合物的谱图中增加了其他分子（例如 2-丁酮、乙酸乙酯、乙酸、乙酰基、丁酸、乙酯、丁酸和 2,3-丁二醇），主要归因于微生物代谢。
