Behavior of Listeria monocytogenes and Other Microorganisms in Sliced Riojano Chorizo (Spanish Dry-Cured Sausage) during Storage under Modified Atmospheres

Abstract

Sliced ready-to-eat meat products packaged under modified atmospheres are often marketed since they cover consumer demands. The slicing process could be a potential risk for consumers since contamination with Listeria monocytogenes could occur during this stage. The current study evaluated the behavior of L. monocytogenes and other microorganisms in commercial sliced Riojano chorizo. This meat product was sliced and inoculated with L. monocytogenes (3.5 log CFU/g) before packaging under different atmospheres (air, vacuum, 100% N2, 20% CO2/80% N2 and 40% CO2/60% N2) and stored at 4 °C for up to 60 days. Samples were taken on days 0, 7, 21, 28 and 60 of storage. L. monocytogenes, mesophiles, Enterobacteriaceae, lactic acid bacteria, Micrococcaceae, molds and yeast counts were evaluated. Additionally, water activity, humidity and pH were determined. L. monocytogenes counts decreased in inoculated sliced chorizo during storage. Packaging conditions and day of storage influenced microbial counts. After 60 days, a significant reduction (p ≤ 0.05) in the initial Listeria contamination levels (3.5. log CFU/g) between 1.1 and 1.46 logarithmic units was achieved in the sausages packaged in modified atmosphere. The highest reductions were observed in slices packaged in 40% CO2/60% N2 after 60 days of storage at 4 °C.

Behaviour of Listeria monocytogenes and Natural Microflora during the Manufacture of Riojano Chorizo (Spanish Dry Cured Sausage)

“…The strains were selected considering the serotypes most often involved in listeriosis outbreaks and those most often found in meat processing plants [ 12 , 31 , 32 ]. A cocktail of the three strains was prepared as follows: each strain was grown in Brain Heart infusion broth (Oxoid, Hampshire, UK) at 30 °C for 18 h as described by Gonzalez-Fandos et al [ 3 ]. Then, the inoculation cocktail was made by mixing equal levels of the individual cultures in 0.1% peptone water (Merck, Darmstadt, Germany) in a sterile container.…”

“…Chorizo is one of the most popular Spanish dry-cured sausages. Above 30 different kinds of chorizo have been described based on varying methods of production (temperature during fermentation and drying stages, addition or not of starter cultures) and combinations of ingredients [ 1 , 2 , 3 ]. Riojano Chorizo is a traditional dry cured sausage made in La Rioja, Spain, that obtained the Protected Geographical Indication (PGI) status in 2010 (EC 249/2010) [ 4 ].…”

“…Nitrites or sugars are not added to this kind of sausage. The manufacturing process includes low temperatures at the initial stages [ 3 ]. Riojano chorizo is often manufactured with traditional technologies without adding starter cultures.…”

“…The microbiological quality of Riojano chorizo depends on the combined effect of low water activity, pH and the presence of sodium chloride and other ingredients such as garlic and paprika, which could inhibit undesired bacteria [ 1 ]. In addition, the temperatures during fermentation and drying play a role on the microbial populations during the different stages of the process [ 3 ]. As sugars and nitrites are not added to Riojano chorizo and the first stages of manufacturing are carried out at low temperatures, its characteristics differ from other types of chorizo.…”

“…Listeria monocytogenes and Salmonella can contaminate pork meat and may be present in dry-cured meat products [ 9 , 10 ]. Other pathogenic microorganisms such as Clostridium botulinum , Clostridium perfringens , Staphylococcus aureus and Escherichia coli have also been found in dry-cured sausages [ 3 , 9 , 10 ]. During the ripening and drying process, a reduction in pathogen levels has been reported depending on the composition and processing conditions [ 10 ].…”