International audienceMeat fatty acid composition is influenced by genetic factors, although to a lower extent than dietary factors. The species is the major source of variation in fatty acid composition with ruminant meats being more saturated as a result of biohydrogenation in the rumen compared to the meat of monogastric animals. The level of fatness also has an effect on the meat fatty acid composition. The contents of saturated (SFA) and monounsaturated (MUFA) fatty acids increase faster with increasing fatness than does the content of PUFA, resulting in a decrease in the relative proportion of PUFA and consequently in the polyunsaturated/saturated fatty acids (P/S) ratio. The dilution of phospholipids with triacylglycerols and the distinct differences in fatty acid composition of these fractions explain the decrease in the P/S ratio with increasing fatness. An exponential model was fitted to the literature data for beef and showed a sharply increasing P/S ratio at low levels of intramuscular fat. Lowering the fat level of beef is thus more efficient in increasing the P/S ratio than dietary interventions. For pork, the intramuscular fat level also affects the P/S ratio, but nutrition will have a larger impact. The fat level also influences the n-6/n-3 PUFA ratio, due to the difference of this ratio in polar and neutral lipids. However, these effects are much smaller than the effects that can be achieved by dietary means. Differences in fatty acid composition between breeds and genotypes can be largely explained by differences in fatness. However, after correction for fat level, breed or genotype differences in the MUFA/SFA ratio and in the longer chain C20 and C22 PUFA metabolism have been reported, reflecting the possible genetic differences in fatty acid metabolism. Breed differences in meat conjugated linoleic acid (CLA) content have not yet been reported, but the c9t11CLA content in meat is positively related to the total fat content. Heritabilities and genetic correlations for the proportion of certain fatty acids have been estimated in a few studies, and correspond to the observations at the phenotypic level in relation to the intramuscular fat level. Although there is potential for genetic change, incorporating fatty acid composition as a goal in classical breeding programs does not seem worthwhile at the present. Enzyme activities have been measured in a few studies, but are not able to explain between-animal variation in fatty acid composition. Biochemical and molecular genetic studies should be encouraged to unravel the mechanisms responsible for differences in the metabolism and incorporation of specific fatty acids in meat.Influence des facteurs génétiques et de l'état d'engraissement sur la composition en acides gras de la viande. Revue. La composition en acides gras de la viande est affectée par divers facteurs : des facteurs nutritionnels, mais aussi des facteurs génétiques, quoiqu'à un degré moindre. L'espèce animale est également une source de variation importante, c'est même la plus importante. La viande des ruminants est plus riche en acides gras saturés que celle des monogastriques, en raison de la biohydrogénation dans le rumen. L'état d'engraissement a aussi un effet très net sur la composition en acides gras. La teneur en acides gras saturés (AGS) et monoinsaturés (AGMI) croît plus rapidement que celle en acides gras polyinsaturés (AGPI) lorsque l'état d'engraissement augmente, ce qui résulte en une diminution de la proportion des AGPI et par conséquent un rapport acides gras polyinsaturés/saturés (P/S) amoindri. Cette baisse du rapport P/S associée à une augmentation du taux de gras intramusculaire peut s'expliquer par la diminution du rapport phospholipides/triglycérides dans les lipides totaux et la composition en acides gras différente de ces deux fractions. Un modèle exponentiel a été adapté aux données de la littérature pour la viande de boeuf et a montré une augmentation nette du rapport P/S lorsque les teneurs en gras intramusculaire sont faibles. La diminution de la teneur en lipides de la viande de boeuf est donc plus efficace pour augmenter le rapport P/S que l'intervention de paramètres nutritionnels. Pour la viande de porc, le taux de gras intramusculaire a également un effet sur le rapport P/S, mais les facteurs nutritionnels auront un effet plus prononcé. Le taux de gras intramusculaire peut aussi influencer le rapport n-6/n-3 AGPI, en raison des différences dans ce rapport entre les phospholipides et les triglycérides. Néanmoins, cet effet est beaucoup moins important que les effets qui peuvent être obtenus avec les paramètres nutritionnels. La mise en évidence de différences dans la composition en acides gras entre les races et les génotypes peut s'expliquer en grande partie par la variabilité de l'état d'engraissement. Cependant, en introduisant un facteur correctif correspondant au dépôt de gras, des différences entre races et génotypes persistent pour le rapport AGMI/AGS et pour le métabolisme des acides gras à chaîne longue (C20 et C22), reflétant de possibles dissemblances génétiques dans le métabolisme des acides gras. Entre races, aucune différence n'a été rapportée, à ce jour, pour la teneur en acides linoléiques conjugués (ACL), mais le taux de l'isomère cis-9 trans-11 dans la viande semble être positivement corrélé à la teneur en gras total. Des études ont estimé les héritabilités et les corrélations...

This paper provides an overview on steered fermentation processes to release phenolic compounds from plant-based matrices, as well as on their potential application to convert phenolic compounds into unique metabolites. The ability of fermentation to improve the yield and to change the profile of phenolic compounds is mainly due to the release of bound phenolic compounds, as a consequence of the degradation of the cell wall structure by microbial enzymes produced during fermentation. Moreover, the microbial metabolism of phenolic compounds results in a large array of new metabolites through different bioconversion pathways such as glycosylation, deglycosylation, ring cleavage, methylation, glucuronidation and sulfate conjugation, depending on the microbial strains and substrates used. A whole range of metabolites is produced, however metabolic pathways related to the formation and bioactivities, and often quantification of the metabolites are highly underinvestigated. This strategy could have potential to produce extracts with a high-added value from plant-based matrices.

Flavonoids are a group of polyphenols that provide health-promoting benefits upon consumption. However, poor bioavailability has been a major hurdle in their use as drugs or nutraceuticals. Low bioavailability has been associated with flavonoid interactions at various stages of the digestion, absorption and distribution process, which is strongly affected by their molecular structure. In this review, we use structure–activity/property relationship to discuss various flavonoid interactions with food matrices, digestive enzymes, intestinal transporters and blood proteins. This approach reveals specific bioactive properties of flavonoids in the gastrointestinal tract as well as various barriers for their bioavailability. In the last part of this review, we use these insights to determine the effect of different structural characteristics on the overall bioavailability of flavonoids. Such information is crucial when flavonoid or flavonoid derivatives are used as active ingredients in foods or drugs.

The effect of double-muscling (DM) genotype (double-muscling, mh/mh; heterozygous, mh/+; normal, +/+) of Belgian Blue (BB) young bulls on the intramuscular fatty acid composition, in particular conjugated linoleic acid (CLA) and polyunsaturated fatty acids (PUFA) was examined in five different muscles. The relative fatty acid composition showed only minor differences between muscles within genotypes. However, the DM genotype had a large effect on both the intramuscular total fatty acid content and on the relative fatty acid composition. Across muscles, the mh/mh animals had a lower total fatty acid content compared with the +/+animals (907 v: 2656 mg/100 g muscle;P< 0·01) and a higher PUFA proportion in total fatty acids (27·5 v 11·3 g/100 g total fatty acids;P< 0001), resulting in a higher PUFA/saturated fatty acid ratio (0·55 v 0·18;P< 0·01) and a lower n-6/n-3 ratio (5·34 v. 6·17;P< 0·01). The heterozygous genotype was intermediate between the two homozygous genotypes. The relative CLA content was similar in the mh/mh and +/+ genotypes and approximated 0·4 to 0·5 g/100 g total fatty acids. From the data it is further suggested that differences in the metabolism of the n-3 and n-6 fatty acids could exist between DM genotypes.