Underlying evidence for the health benefits of fermented foods in humans.

Fermented foods (FFs) have been a part of our diets for millennia and comprise highly diverse products obtained from plants and animals all over the world. Historically, fermentation has been used to preserve food and render certain raw materials edible. As our food systems evolve towards more sustainability, the health benefits of FFs have been increasingly touted. Fermentation generates new/transformed bioactive compounds that may occur in association with probiotic bacteria. The result can be specific, advantageous functional properties. Yet, when considering the body of human studies on the topic, whether observational or experimental, it is rare to come across findings supporting the above assertion. Certainly, results are lacking to confirm the widespread idea that FFs have general health benefits. There are some exceptions, such as in the case of lactose degradation via fermentation in individuals who are lactose intolerant; the impact of select fermented dairy products on insulin sensitivity; or the benefits of alcohol consumption. However, in other situations, the results fail to categorically indicate whether FFs have neutral, beneficial, or detrimental effects on human health. This review tackles this apparent incongruity by showing why it is complex to test the health effects of FFs and what can be done to improve knowledge in this field.

Lactobacillus role during conditioning of refrigerated and vacuum-packaged Argentinean meat.

The role of Lactobacillus strains with bioprotective and technological potential on raw beef during 15days of storage under vacuum at 7°C was investigated. The assayed strains were able to grow on the meat, Lactobacillus curvatus CRL705 and Lactobacillus sakei 23K showing the highest competitiveness. A net increase of amino acids was determined in inoculated samples when compared to the control, this being maximal for Lactobacillus plantarum CRL681. Although an important endogenous activity of meat sarcoplasmic proteins was observed, the disappearance of protein bands and the generation of a new one were detected as a consequence of Lactobacillus growth. A synergistic effect of Lactobacillus in combination with the muscle proteolytic enzyme complex can be suggested. From the studied strains, the bacteriocin producer L. curvatus CRL705 may be considered as a good candidate to contribute to meat ageing by means of small peptides and free amino acids generation while improving shelf life.

Lactobacillus sakei: recent developments and future prospects.

Lactobacillus sakei is one of the most important bacterial species involved in meat preservation and meat fermentation. In the last fifteen years, numerous studies have focused on this species due to its important role in food microbiology. The present paper reviews current knowledge of this emerging species in the fields of taxonomy, phylogeny and physiology, and metabolism. Recent developments in genetic tools and molecular genetics will also be emphasized to evaluate future prospects.

Protein expression under uracil privation in Lactobacillus sakei.

Lactobacillus sakei is a lactic acid bacterium belonging to the natural flora of fresh and vacuum-packed meat, and is used as the starter for manufacturing fermented sausages. This species is now being studied at the genetic level. We investigated uracil prototrophy of strain 23K in order to validate the proteomic approach to study metabolism regulations. Cells grown without uracil had lower growth rates than with uracil. Protein analysis by 2D gel electrophoresis showed that at least three polypeptides were specifically induced in the absence of uracil. Two of these polypeptides were identified as orotate phosphoribosyl transferase, catalyzing the fifth step of pyrimidine biosynthesis, and PyrR, the transcriptional regulator of the pyr operon, respectively.

Relationships between arginine degradation, pH and survival in Lactobacillus sakei.

Lactobacillus sakei is one of the most important lactic acid bacteria of meat and fermented meat products. It is able to degrade arginine with ammonia and ATP production by the arginine deiminase pathway (ADI). This pathway is composed of three enzymes: arginine deiminase, ornithine transcarbamoylase and carbamate kinase, and an arginine transport system. The transcription of the ADI pathway is induced by arginine and subjected to catabolite repression. In order to understand the physiological role of the degradation of this amino acid we investigated the growth of bacteria under various conditions. We show that arginine degradation is responsible for an enhanced viability during the stationary phase when cells are grown under anaerobiosis. Arginine is necessary for the induction of the ADI pathway but in association with another environmental signal. Using a mutant of the L-lactate dehydrogenase unable to lower the pH we could clearly demonstrate that (i) low pH is not responsible for cell death during the stationary phase, so survival is due to another factor than elevated pH, (ii) neither low pH nor oxygen limitation is responsible for the induction of the ADI pathway together with arginine since the ldhL mutant is able to degrade arginine under aerobiosis.

Quantification and efficiency of Lactobacillus sakei strain mixtures used as protective cultures in ground beef.

Lactobacillus sakei is a lactic acid bacterium, naturally associated with long term storage of fresh meat at low temperature. Here we investigated the effect, on the evolution of pathogenic and spoilage microorganisms in ground beef, of L. sakei cocktails used as bioprotective cultures. We selectively developed a real time quantitative PCR method, allowing the quantification of individual L. sakei strains inoculated in ground meat with specific probes. Six cocktails of three strains were tested to evaluate their effect on the growth of Salmonella enterica Typhimurium, Escherichia coli O157:H7 and Brochothrix thermosphacta at 4°C and 8°C, under vacuum or modified atmosphere packaging. Using plating methods to quantify the different bacterial species, one cocktail showed an effect against S. Typhimurium and E. coli under given conditions. Real time quantitative PCR showed that the three inoculated L. sakei strains had a different growth pattern, and that the association of these three strains indeed impaired growth of S. Typhimurium and E. coli.