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. 2018 Sep 2;280:78-86. doi: 10.1016/j.ijfoodmicro.2018.04.041. Epub 2018 Apr 28.
Ten lots of industrial raw sausages in modified atmosphere (CO 30%, O 70%), produced in the same plant over 7 months, were analyzed at the day after production (S samples) and at the end of shelf life (E samples), after 12 days storage at 7 °C to simulate thermal abuse. Quality of the products was generally compromised by storage at 7 °C, with only 3 E samples without alterations. During the shelf life, the pH decreased for the accumulation of acetic and lactic acids. A few biogenic amines accumulated, remaining below acceptable limits. The profile of volatile compounds got enriched with alcohols, ketones, and acids (e.g. ethanol, 2,3-butanediol, 2,3-butandione, butanoic acid) originated by bacterial metabolism. Throughout the shelf life, aerobic bacteria increased from 4.7 log to 6.6 log cfu/g, and lactic acid bacteria (LAB) from 3.7 to 8.1 log cfu/g. Staphylococci, enterobacteria, and pseudomonads passed from 3.7, 3.0, and 1.7 to 5.5, 4.8, and 3.0 log cfu/g, respectively. Dominant cultivable LAB, genotyped by RAPD-PCR, belonged to the species Lactobacillus curvatus/graminis and Lactobacillus sakei, with lower amounts of Leuconostoc carnosum and Leuconostoc mesenteroides. Brochothrix thermosphacta was the prevailing species among aerobic bacteria. The same biotypes ascribed to several different species where often found in E samples of diverse batches, suggesting a recurrent contamination from the plant of production. Profiling of 16S rRNA gene evidenced that microbiota of S samples clustered in two main groups where either Firmicutes or Bacteroidetes prevailed, albeit with taxa generally associated to the gastro-intestinal tract of mammals. The microbial diversity was lower in E samples than in S ones. Even though a common profile could not be identified, most E samples clustered together and were dominated by Firmicutes, with Lactobacillaceae and Listeriaceae as the most abundant families (mostly ascribed to Lactobacillus and Brochothrix, respectively). In a sole E sample Proteobacteria (especially Serratia) was the major phylum.
10 批工业原料香肠(CO30%,O70%),在同一工厂生产,经过 7 个月的时间,在生产后第 1 天(S 样品)和保质期结束时(E 样品)进行了分析,在 7°C 下储存 12 天以模拟热滥用。产品质量在 7°C 下储存普遍受损,只有 3 个 E 样品没有变化。在保质期内,pH 值下降是由于乙酸和乳酸的积累。一些生物胺积累,但仍低于可接受的限度。挥发性化合物的谱图中富集了醇、酮和酸(例如乙醇、2,3-丁二醇、2,3-丁二酮、丁酸),这些物质来源于细菌代谢。在整个保质期内,需氧细菌从 4.7 对数增加到 6.6 对数 cfu/g,乳酸菌(LAB)从 3.7 对数增加到 8.1 对数 cfu/g。葡萄球菌、肠杆菌和假单胞菌从 3.7、3.0 和 1.7 对数分别增加到 5.5、4.8 和 3.0 对数 cfu/g。占优势的可培养 LAB 通过 RAPD-PCR 进行基因分型,属于弯曲乳杆菌/革兰氏乳杆菌和德式乳杆菌,数量较少的有肠膜明串珠菌和肠系膜明串珠菌。需氧细菌中主要的是嗜热解糖梭菌。在不同批次的 E 样品中经常发现属于不同种的相同生物型,这表明生产工厂存在反复污染。16S rRNA 基因分析表明,S 样品的微生物群聚成两个主要的组,其中一个以厚壁菌门为主,另一个以拟杆菌门为主,尽管通常与哺乳动物的胃肠道有关。E 样品的微生物多样性低于 S 样品。尽管无法确定共同的模式,但大多数 E 样品聚集在一起,以厚壁菌门为主,乳杆菌科和李斯特菌科最为丰富(主要归因于乳杆菌和布氏杆菌)。在一个单独的 E 样品中,变形菌门(特别是沙雷氏菌)是主要的门。