Bacterial community of industrial raw sausage packaged in modified atmosphere throughout the shelf life.
Ten lots of industrial raw sausages in modified atmosphere (CO2 30%, O2 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.
['Raimondi|Stefano|S|', 'Nappi|Maria Rosaria|MR|', 'Sirangelo|Tiziana Maria|TM|', 'Leonardi|Alan|A|', 'Amaretti|Alberto|A|', 'Ulrici|Alessandro|A|', 'Magnani|Rudy|R|', 'Montanari|Chiara|C|', 'Tabanelli|Giulia|G|', 'Gardini|Fausto|F|', 'Rossi|Maddalena|M|']
D019342:Acetic Acid D000818:Animals D001419:Bacteria D015169:Colony Count, Microbial D005516:Food Microbiology D018857:Food Packaging D005519:Food Preservation D061353:Food Storage D019344:Lactic Acid D008461:Meat Products D064307:Microbiota D012336:RNA, Ribosomal, 16S D019105:Random Amplified Polymorphic DNA Technique D055549:Volatile Organic Compounds
Sausage Shelf life 16S rRNA gene profiling MAP Raw meat Spoilage