La revue Viandes et produits carnés

La revue française de la recherche en viandes et produits carnés  ISSN  2555-8560




Combined use of biopreservation and high pressure to ensure the microbiological safety of refrigerated meat products

Within the framework of the ANR BlacHP project, the effectiveness of a protective culture combined to a high-pressure treatment selected following laboratory scale tests was evaluated under industrial conditions. First, the implantation of the protective culture concomitant with the control of a pathogenic flora (Listeria monocytogenes) or spoiled psychrophilic spore-forming flora was validated in the cooked ham using the challenge-test methodology. In parallel, absence of organoleptic modifications of the product treated by the combined process was checked. In a second step, the developed process was successfully transferred to three other meat products, ensuring microbiological quality and safety over their entire microbiological shelf life.

High Pressure Processing combined with biopreservation: impact on cured ham characteristics

BLacHP project (ANR-14-CE20-0004) aims to develop a strategy to stabilize meat products with reduced nitrite content; experiments were carried out on cooked ham with 25 ppm of nitrites. The strategy adopted the combination of two hurdle technologies: biopreservation by Lactococcus lactis and high pressure processing (500 MPa, 5 min).
The combined treatment has moderate impact on the technological parameters of the cooked ham (water retention, exudation, texture, color). The evaluation of oxidation products shows that the combined treatment induces a low oxidation of lipids and proteins during refrigerated storage. Moreover, the use of the combined treatment increases the protein digestion rate. Then, biopreservation combined with high pressure processing makes possible to maintain the quality of reduced nitrite content cooked ham close to that of traditional cooked ham, and ensures its sanitary safety.

Use of bacterial consortia or complex microbiota as a model for understanding microbial interactions in meat products: advantages and limitations.

The microbiological study of food is limited because of the variability between samples (species diversity and abundance) and the presence of unknown or yet non cultivated bacteria. Two approaches exist to circumvent this. One constitutes strain cocktails from pure cultures in simplified food models that enable mathematical modeling. The second collects natural food microbiota without a prior culture step. For this, modeling is more difficult but microbiota are reproducible and closer to the food reality. The complementarity of these two approaches is discussed.

Stabilization of bacterial contaminants in cooked hams after high-pressure treatment and addition of a protective culture

Bacterial communities present on diced cooked ham were characterized. They were dominated either by Firmicutes or by proteobacteria, with some species that have not yet been cultivated. Their dynamics after high-pressure treatment and addition of a protective culture was monitored. Although each bacterial community reacts differently to the treatments, the combination of high pressure and biopreservation indeed stabilizes the product with overgrowth of the protective culture.

Presentation of the project BLacHP (2015-2019)

Refrigerated meat products are perishables with a reduced storage life. In addition, vacuum-packed storage or with a modified atmosphere at refrigerated temperatures may provide a selective advantage to the development of psychotrophic sporulating bacteria from the Bacillus and Clostridium genera. Thus, preservatives, such as nitrites, are often necessary to ensure the safety of refrigerated products with low acidity during their storage life. Pressure by society to reduce chemical inputs in ready-to-eat food products is behind the BLac HP project whose aim is to develop a new strategy for the stabilization of refrigerated transformed meat products by combining high pressure (HP) and biopreservation with lactic bacteria. Using a multidisciplinary approach, our work has allowed the study of a combination of processes on several levels: cell, psychrophic spore species from Bacillus and Clostridium genera selected for a project and on the ecosystem scale. The dynamic response of microbial ecosystems to the processes was explored using molecular biology methods. At the same time, the effect of the processes on nutritional, technological and organoleptic properties of ham cubes was also evaluated. In addition, the environmental and societal impacts of the combination of the processes were evaluated in comparison with a conventional process for cooked ham. Finally, scaling up and transposition to other products have been considered.

Vacuum-packed meats: are the microbiological indicators reliable

Over the years, the bovine meat sector has seen atypical types of preservation means amongst vacuum-packed products (muscles and meat). Indeed, there has been an over-develoment of enterobacteria, an insufficient development of the bio-protective lactic flora, and even both problems without the meat and muscles showing any sensorial alterations. In order to understand this phenomenon and to help the sector avoid it, the French Livestock Institute in partnership with the Caen Normandy University, has led a study on the identification of microbial flora identified during the analysis of ready-to-cut muscle contamination and pieces of precut vacuum-packed meats after ageing under controlled conditions. The results obtained showed that in cases of atypical preservation, with reference methods, when the compliance threshold of the “enterobacteria” criteria is exceeded, it is the over-develoment of enterobacteria and notably the Hafnia alvei species that is responsible. However, the apparent under-development of lactic flora was caused by the exclusion of lactic bacteria of the genus Carnobacterium sp. and Lactococcus sp., causing an under-estimation of the real amounts of lactic flora present. This study has therefore provided evidence that a whole part of meats and muscles conditioned and preserved with vacuum-packed packaging is excluded from the marketing channels due to an error in the reference method that quantifies the lactic bacteria, therefore inducing an under-estimation of this compliance criterion for meat products. In order to remedy this problem, the French Breeding Institute and Interbev are working to develop alternative methods for the more precise evaluation of lactic bacteria present on the surface of meats.

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