La revue Viandes et produits carnés

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




Microbiological security of beef

The bovine gastrointestinal tract is the main reservoir for enterohaemorrhagic Escherichia coli (EHEC) responsible for food-borne infections. Some compounds (carbohydrates included in the mucus layer, ethanolamine from the membranes of epithelial cells or bacteria) are required for an optimal growth of EHEC in the intestine of ruminants. Bacterial strains, such as probiotics, with a high affinity for these compounds, could be added into the ruminant diet, depriving EHEC strains of these nutrients and consequently limiting the shedding of EHEC in animals and food contamination.
We show that EHEC use sugar coming from the mucus layer of the intestine very efficiently. The EHEC strains need to assimilate mannose, N-acetyl-glucosamine, N-acetyl neuraminic acid and galactose for maximal growth. In addition, we show that the use of ethanolamine (EA) as a source of nitrogen is also required for an optimal development of EHEC in the animal’s intestine. EA is a major component of the cell membrane of animals, plants and bacteria that can be released in the digestive tract of the ruminant.
Although EHEC strains are present in small quantities in the intestine, they assimilate mannose, N-acetyl glucosamine and N-acetyl neuraminic acid more rapidly and efficiently than the bacteria of the intestinal microbiota, even though the enzymes necessary for assimilating EA are absent from the microbiota bacteria. The EHEC strains have therefore specialized themselves in the use of compounds that are poorly or not assimilated by the bacteria of the intestinal microbiota, therefore creating an ecological niche for EHEC strains.
Studies must be performed to identify the probiotic strains (yeast or lactic acid bacteria) that compete with EHEC for these different components. These probiotics, added in large quantities to an animal’s diet, will therefore deprive the EHEC strains of important nutrients therefore limiting the carriage of EHEC strains by the animal and contamination of food.

Discoloration of veal ribs

Bone discoloration is a serious issue for the veal meat industry: storing veal ribs in a high-oxygen modified atmosphere packaging may result in bone marrow oxidation, therefore darkening the bone. This study dealt with the impact of three processing factors on bone discoloration during storage.
The cooling of the ribs (to facilitate slicing), the delay between slaughter and carcass cutting, the length of meat maturation before cutting and conditioning of the ribs were studied. Two trials were carried out: one compared two cooling methods (20 min at -25°C and 1 night at -2°C) and the other two different time intervals between slaughtering and carcass cutting (1 to 3 days) crossed with two different lengths of meat maturation before cutting and conditioning (4 to 6 days). The ribs were stored for 8 days at +2°C then 3 days at +8°C. Observations were made on days 3, 5, 7, 9 and 11 after conditioning. The discoloration of the bones was determined using sensorial (a professional jury) and instrumental (Colorimeter CR 400) methods.
The results show that cooling is an important step for bone discoloration: cooling for one night at -2°C is detrimental as compared to cooling for 20 minutes at -25°C. However, increasing maturation time does not seem to have an impact: both maturation times (1 and 3 days) can be used. Increasing meat maturation from 4 to 6 days before cutting slightly discolors the bones.  
Therefore rapid cooling associated with a short maturation time should allow decreasing discoloration of bones during storage of veal ribs.

Meat and human health

Many studies have examined the influence of meat consumption on human health. Meat eaters have a higher body mass index and more weight gain than vegetarians. The risk of type 2 diabetes has also been linked to high meat consumption. However, the statistical correlations with these metabolic disorders are weak. There is inconsistent evidence of a higher cardiovascular risk. In all cases it is difficult to not consider the overall type of food consumed. A link between high meat consumption and cancer, particularly colorectal cancer, has been observed in nearly all epidemiological studies. Some studies have also shown a link with breast, prostate and lung cancer. The mode of cooking could be partly responsible for this effect, due for example to heterocyclic aromatic amines production during grilling and intensive cooking. Quantitative and qualitative advice can be given from these observations.

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