Introduction: Fresh sausage is a perishable product easily colonized by spoilage bacteria. Microbial diversity of fresh sausage has been generally investigated using traditional cultural methods. Purpose: The present study aimed to obtain an exhaustive description of the microbiota composition and diversity throughout the shelf life of fresh sausage. Methods: Cultivable bacteria from ten batches of sausage provided by the same factory were enumerated on PCA, MRS, Mac Conkey, ALOA, and PDA plates, at delivery and after 12 days at 7°C. The dominant strains were genotyped by RAPD-PCR fingerprinting, and taxonomic diversity was estimated by partial sequencing of 16S rRNA genes. A comprehensive picture of bacteria was obtained by metataxonomic analysis of Illumina 16S sequences. Results: The mean charge (log of CFU/g) of cultivable aerobic and aerotolerant bacteria started at 5.0 and reached 7.2 after 12 days at 7°C, with a concomitant drop of pH from 5.9 to 5.5. Lactic acid bacteria showed the highest increase starting from 4.1 and reaching 8.6 log, followed by Staphylococci (4.0 to 6.5 log) and by Enterobactericeae (3.2 to 6.2 log). The majority of MRS biotypes belonged to Lactobacillus curvatus, followed by Lactobacillus sakei, Leuconostoc carnosum, and Leuconostoc mesenteroides. The most represented species in PCA was Brochotrix thermosphacta. Metataxonomic analysis revealed that at packaging, fresh sausage was characterized by bacteria generally ascribable to two diverse microbiota associated with gut microbes. At the end of the shelf life, Firmicutes dominated the microbiota, in some cases with prevalence of Lactobacillales. In other samples, Listeriaceae took over, with Brochothrix being the most represented genus. Enterobacteriaceae, generally ascribed to Serratia, were abundant in a few samples at the end of the shelf life. Significance: This study provided a wide overview of microbiota evolution in fresh sausage, shedding light on meat hygiene and safety issues.
Changes in Microbiota of Fresh Sausage Throughout Shelf Life / Raimondi, Stefano; Sirangelo, TIZIANA MARIA; Gardini, Fausto; Luciani, Rosaria; Amaretti, Alberto; Magnani, Rudy; Rossi, Maddalena. - (2018). (Intervento presentato al convegno IAFP'S European Symposium on Food Safety tenutosi a Sweden nel 25-27 April).
Changes in Microbiota of Fresh Sausage Throughout Shelf Life
Raimondi Stefano;Sirangelo Tiziana Maria;Gardini Fausto;Luciani Rosaria;Amaretti Alberto;Rossi Maddalena
2018
Abstract
Introduction: Fresh sausage is a perishable product easily colonized by spoilage bacteria. Microbial diversity of fresh sausage has been generally investigated using traditional cultural methods. Purpose: The present study aimed to obtain an exhaustive description of the microbiota composition and diversity throughout the shelf life of fresh sausage. Methods: Cultivable bacteria from ten batches of sausage provided by the same factory were enumerated on PCA, MRS, Mac Conkey, ALOA, and PDA plates, at delivery and after 12 days at 7°C. The dominant strains were genotyped by RAPD-PCR fingerprinting, and taxonomic diversity was estimated by partial sequencing of 16S rRNA genes. A comprehensive picture of bacteria was obtained by metataxonomic analysis of Illumina 16S sequences. Results: The mean charge (log of CFU/g) of cultivable aerobic and aerotolerant bacteria started at 5.0 and reached 7.2 after 12 days at 7°C, with a concomitant drop of pH from 5.9 to 5.5. Lactic acid bacteria showed the highest increase starting from 4.1 and reaching 8.6 log, followed by Staphylococci (4.0 to 6.5 log) and by Enterobactericeae (3.2 to 6.2 log). The majority of MRS biotypes belonged to Lactobacillus curvatus, followed by Lactobacillus sakei, Leuconostoc carnosum, and Leuconostoc mesenteroides. The most represented species in PCA was Brochotrix thermosphacta. Metataxonomic analysis revealed that at packaging, fresh sausage was characterized by bacteria generally ascribable to two diverse microbiota associated with gut microbes. At the end of the shelf life, Firmicutes dominated the microbiota, in some cases with prevalence of Lactobacillales. In other samples, Listeriaceae took over, with Brochothrix being the most represented genus. Enterobacteriaceae, generally ascribed to Serratia, were abundant in a few samples at the end of the shelf life. Significance: This study provided a wide overview of microbiota evolution in fresh sausage, shedding light on meat hygiene and safety issues.
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