Sorption of Grape Proanthocyanidins and Wine Polyphenols by Inactivated Yeast Fractions

Sorption of Grape Proanthocyanidins and Wine Polyphenols by Inactivated Yeast Fractions. 65. ASEV National Conferenc

Sorption of grape proanthocyanidins and wine polyphenols by yeasts, inactivated yeasts, and yeast cell walls

Inactivated yeast fractions (IYFs) can be used in enology to improve the stability and mouthfeel of red wines. However, information concerning the mechanisms involved and the impact of the IYF characteristics is scarce. Adsorption isotherms were used to investigate interactions between grape proanthocyanidin fractions (PAs) or wine polyphenols (WP) and a commercial yeast strain (Y), the inactivated yeast (IY), the yeast submitted to autolyzis and inactivation (A-IY), and the cell walls obtained by mechanical disruption (CW). High affinity isotherms and high adsorption capacities were observed for grape PAs and whole cells (Y, IY, and A-IY). Affinity and adsorbed amount were lower with wine PAs, due to chemical changes occurring during winemaking. By contrast to whole cells, grape PAs and WP adsorption on CW remained very low. This raises the issue of the part played by cell walls in the interactions between yeast and proanthocyanidins and suggests the passage of the latter through the wall pores and their interaction with the plasma membrane

Impact of grape variety, berry maturity and size on the extractability of skin polyphenols during model wine-like maceration experiments

International audienceBackground : Skin cell walls modulate anthocyanin and tannin extraction from grape skins. However, relationships between the composition of alcohol insoluble cell wall solids (AIS) and extraction are still unclear. Our objectives were to characterize the impact of variety, berry size and ripeness on skin AIS composition (polysaccharides, proteins) and polyphenol extraction during maceration. Results. The grape skin composition and its impact on polyphenol extraction was compared for two varieties, Carignan and Grenache, with skins of berries sorted according to their size and density. Extractions were performed in model wine-like maceration conditions. Fresh skins had similar contents in polymeric tannins, but strongly differed by their anthocyanin contents (higher in Carignan and in the ripest berries) and composition (higher proportions in coumaroylated anthocyanins in Carignan). Anthocyanin extraction was proportionally much higher in Grenache, which was not just related to the Carignan's higher levels in coumaroylated anthocyanins. Chemical reactions decreased anthocyanin concentrations in solution for both varieties. Tannin extraction for Grenache was slightly higher and faster than for Carignan. Skin AISs differed slightly between the two varieties by their carbohydrate composition and protein content, but not between modalities. Polyphenol analyses in the precipitates evidenced at the end of the maceration and in residual skins highlighted differences between the two varieties and between berries with different ripeness. Conclusion : Structural information on the cell wall network and on its changes during maceration, along with a better understanding of the chemical reactions of anthocyanins and tannins is needed to better relate grape and wine polyphenol composition

Anthracnose du poids protéagineux (M.pinodes): nuisibilité de la maladie à partir des semences contaminées

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Anthracnose du pois protéagineux (M. pinodes): nuisibilité de la maladie à partir des semences contaminées

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Role of seed infection by the Ascochyta blight pathogen of dried pea (Mycosphaerella pinodes) in seedling emergence, early disease development and transmission of the disease to aerial plant parts

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Interactions of grape proanthocyanidins and wine polyphenols with yeast protein extract

Interactions of grape proanthocyanidins and wine polyphenols with yeast protein extract . In vino analytica Scientia 201

Impact of the variety on the adsorption of anthocyanins and tannins on grape flesh cell walls

International audienceBACKGROUND: During winemaking, after extraction from the skins, anthocyanins and tannins adsorb onto the pulp flesh cell walls. The present study aimed to quantify the amounts adsorbed and their impact on wine composition, the impact of variety and ethanol on adsorption, and whether the presence of anthocyanins plays a role and impacts tannin adsorption. RESULTS: Anthocyanin and tannin fractions obtained by mimicking winemaking conditions were mixed with fresh flesh cell walls of two varieties: Carignan and Grenache. Adsorption isotherms were measured. Adsorption of tannins was higher with Carignan than with Grenache and decreased when the ethanol content increased. In comparison, anthocyanins were adsorbed in small amounts, and their mixing with tannins had no impact on their adsorption. The differences were related to differences in pulp cell wall composition, particularly in terms of extensins and arabinans. CONCLUSION: Adsorption of tannins, which can reach 50% of the initial amount, depends on the pulp cell wall composition. This needs to be investigated further

Ascochyta blight (Mycosphaerella pinodes) of Pisum sativum: relationship between symptoms on pods and seeds infection rate

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Fat-soluble vitamin intestinal absorption: Absorption sites in the intestine and interactions for absorption

International audienceThe interactions occurring at the intestinal level between the fat-soluble vitamins A, D, E and K (FSVs) are poorly documented. We first determined each FSV absorption profile along the duodenal-colonic axis of mouse intestine to clarify their respective absorption sites. We then investigated the interactions between FSVs during their uptake by Caco-2 cells. Our data show that vitamin A was mostly absorbed in the mouse proximal intestine, while vitamin D was absorbed in the median intestine, and vitamin E and K in the distal intestine. Significant competitive interactions for uptake were then elucidated among vitamin D, E and K, supporting the hypothesis of common absorption pathways. Vitamin A also significantly decreased the uptake of the other FSVs but, conversely, its uptake was not impaired by vitamins D and K and even promoted by vitamin E. These results should be taken into account, especially for supplement formulation, to optimise FSV absorption