Lactococcus lactis and Lactobacillus sakei as bio-protective culture to eliminate Leuconostoc mesenteroides spoilage and improve the shelf life and sensorial characteristics of commercial cooked bacon

doi:10.1016/j.fm.2016.03.001

Food Microbiology

Volume 58, September 2016, Pages 16-22

https://doi.org/10.1016/j.fm.2016.03.001 Get rights and content

Highlights

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The cause of greening and slime formation in cooked bacon was investigated.
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Leuconostoc mesenteroides resulted responsible for spoilage.
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Leuc. mesenteroides produced green colour, slime and various negative compounds.
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Lactococcus lactis spp. lactis and Lactobacillus sakei were able to inhibit the growth of Leuc. mesenteroides.
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Bio-protective culture were able to reduce the risk of spoilage.

Abstract

Cooked bacon is a typical Italian meat product. After production, cooked bacon is stored at 4 ± 2 °C. During storage, the microorganisms that survived pasteurisation can grow and produce spoilage. For the first time, we studied the cause of the deterioration in spoiled cooked bacon compared to unspoiled samples. Moreover, the use of bio-protective cultures to improve the quality of the product and eliminate the risk of spoilage was tested. The results show that Leuconostoc mesenteroides is responsible for spoilage and produces a greening colour of the meat, slime and various compounds that result from the fermentation of sugars and the degradation of nitrogen compounds. Finally, Lactococcus lactis spp. lactis and Lactobacillus sakei were able to reduce the risk of Leuconostoc mesenteroides spoilage.

Introduction

The tradition of Italian charcuterie has ancient origins and is commonly traced back to the Roman period. Forty-three of the 315 typical traditional Italian meat products consist of different types of bacon. The most popular type is cooked bacon. Bacon is derived from the central part of the cover fat from the half of the carcass that goes from the sternal region to the inguinal. The meat is worked in different ways (natural, cured, smoked, or cooked) and then stretched or rolled in shape. The production process is reported in Table 1. The brine is composed of water and various ingredients, such as salt, fructose, dextrose, spices, ascorbic acid (E 316) and nitrate (E 252), depending on the recipe and the concentration of the ingredients. Sucrose may be used, too. The shelf life is approximately 90 days.

After pasteurisation, the microorganisms that survived pasteurisation can grow and spoil the product during storage. The species involved in the spoilage of cooked meats are heterogeneous. Brochothrix thermosphacta, Enterococcus faecalis, Lactobacillus sakei, Leuconostoc mesenteroides subsp. mesenteroides, Leuconostoc carnosum and Carnobacterium divergens are widely known to negatively affect the flavour, texture, and colour of sliced and vacuum packed meat products (Björkroth et al., 1998, Metaxopoulos et al., 2002, Cantoni et al., 2008, Audenaert et al., 2010, Vasilopoulos et al., 2008, Vasilopoulos et al., 2010a, Vasilopoulos et al., 2010b; Comi and Iacumin, 2012, Comi et al., 2014a). Moreover, the growth of heterofermentative bacteria can cause the packaging to swell or rupture due to the presence of CO₂. Bacterial activity is induced by the presence of the sugars that are added with the brine during tumbling, resting, or cooling for a long time. Lactic acid bacteria (LAB) and B. thermosphacta, which can come from the fresh meat, from the handling-related operations during processing or from the environment, are able to produce discolouration, greening and slimes (Björkroth et al., 1998, Audenaert et al., 2010, Vasilopoulos et al., 2010a, Vasilopoulos et al., 2010b, Comi and Iacumin, 2012). Improper cooking and sanitisation practices are frequent in craft cooked meat plants; consequently, the precautions are not effective in eliminating the handling-related post-contamination or the presence of thermotolerant bacteria (Franz and von Holy, 1996, Comi and Iacumin, 2012). Therefore, the use of various post-cooking or post-slicing technologies, such as high pressure, antimicrobial treatments, organic acids and protective cultures, for the bio-preservation of cooked meat products has been suggested (Metaxopoulos et al., 2002, Vermeiren et al., 2004).

The purpose of this study was to identify and characterise the spoilage-associated microorganisms in artisanal cooked bacon and to examine the use of bio-protective cultures to reduce the risk of Leuconostoc mesenteroides spoilage.

Section snippets

Samples and sampling procedures

Two hundred cooked bacon of an artisan meat cooking plant were prepared following the traditional procedures of the plant (the ingredients and concentrations are subject to confidentiality). After cooking, the products were cut into 200 pieces (100 g each), packaged under vacuum, pasteurised at 85 °C for 15 min and stored at 4 ± 2 °C. The packaging film was Combiflex PE/PA 2010 (60/150) (Niederwieser, S.p.a., Italy). The shelf-life of the products is 90 days, but just at 30 days, 40 (20% of

Microbial analysis of spoiled and unspoiled cooked bacon

The concentration of LAB in the spoiled product was significantly different from the concentration in the unspoiled product (p < 0.05). In particular it was 8.7 ± 0.1 CFU/g in spoiled and 4.0 ± 0.2 CFU/g in unspoiled. Similarly, a significant difference (p < 0.05) was observed in the TVC concentration between the spoiled and unspoiled product. The spoiled samples presented a TVC concentration of 6.3 ± 0.3 CFU/g, whereas the unspoiled product presented a TVC concentration of 3.0 ± 0.5 CFU/g. The

Conclusion

Data demonstrated that bio-protective cultures inhibited Leuc. mesenteroides growth and eliminated the greening colour of the meat, the slime, the package inflation, the off-flavours and the off-odours. Therefore, the bio-protective cultures evaluated in this study can improve the shelf life and eliminate the growth of spoilage microorganisms. In particular this is the fisrt time that a Lc. lactis subsp. lactis is used in order to improve the shelf-life of cooked meat as cooked bacon.

Conflict of interest

None of the authors of this paper has a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper.

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Lactococcus lactis and Lactobacillus sakei as bio-protective culture to eliminate Leuconostoc mesenteroides spoilage and improve the shelf life and sensorial characteristics of commercial cooked bacon

Highlights

Abstract

Introduction

Section snippets

Samples and sampling procedures

Microbial analysis of spoiled and unspoiled cooked bacon

Conclusion

Conflict of interest

Food Microbiol.

Meat Sci.

Int. J. Food Microbiol.

Int. J. Food Microbiol.

Food Microbiol.

Food Microbiol.

Meat Sci.

Food Microbiol.

Food Microbiol.

FEMS Microbiol. Rev.

Food Microbiol.

Food Microbiol.

Int. J. Food Microbiol.

Identification and characterization of Leuconostoc carnosum, associated with production and spoilage of vacuum-packaged, sliced, cooked ham

Appl. Environ. Microbiol.

Vecchie e recenti alterazioni di prodotti carnei cotti

Ing. Aliment.

Caratteristiche chimiche e batteriologiche di salami della

Lomellina. Arch. Vet. Ital.

Denaturing gradient gel electrophoresis analysis of the 16S rRNA gene V1 region to monitor dynamic changes in the bacterial population during fermentation of Italian sausages

Appl. Environ. Microbiol.