1,721,112 research outputs found
Facteurs de variabilité des micronutriments de la production à la transformation en lien avec la santé. Exemple des polyphénols.
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Phenolic compound/polysaccharide interactions in plant-based products: organoleptic and nutritional consequences
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SOP for extraction, quantification and analysis of phenol acid components of cassava. Biophysical Characterization of Quality Traits, WP2
Get PDFExploration Of Key Parameters In Colour Stability Of Strawberry-Based Products During Their Transformation And Storage To Avoid Additives And Favour Natural Products
No full textLe nectar de fraise est un produit populaire, mais la stabilité de sa couleur après traitement thermique et au cours du stockage reste un défi. L'objectif principal de cette thèse était d'explorer les paramètres impliqués dans la stabilité de la couleur du nectar de fraise, tels que le cultivar, le stade de maturation, la date de récolte, les conditions de traitement et la durée de stockage. De plus, pour mieux comprendre le mécanisme de stabilité de la couleur des anthocyanes de fraises, l'hydratation de l'ion flavylium rouge et l'autoxydation thermique ont été étudiées dans un système modèle à un pH de 3,6, en présence de différentes fractions de proanthocyanidine (PAC) et de pectines.Comme prévu, les compositions en composés phénoliques et en polysaccharides dépendent du cultivar, du stade de maturation et de la date de récolte. Le mûrissement et la récolte tardive induisent une augmentation des teneurs en anthocyanes et une réduction des teneurs en PAC, alors que les changements dans les autres polyphénols étaient mineurs. Le mûrissement et la récolte favorisent la la perte des chaînes latérales de pectines. La plus grande stabilité de la couleur du nectar a été observée pour les échantillons surmatures de la récolte tardive. La stabilité de la couleur du nectar a été corrélée chez les fraises à une teneur élevée en anthocyanes, à une faible teneur en PACs et à des pectines riches en galactose. Les effets de différentes méthodes de traitement sur les composés phénoliques, la paroi cellulaire et la stabilité de la couleur ont été évalués en comparant le traitement thermique (TT), le traitement à haute pression (HPP) et le champ électrique pulsé (PEF) sur la stabilité de la couleur. Les proanthocyanidines et les anthocyanines sont restées les principales classes phénoliques après le traitement, bien que le stockage ait entraîné une diminution de leurs teneurs, en particulier après le traitement PEF. Les unités constitutives des proanthocyanidines ont été significativement affectées par le traitement et le stockage, en particulier la (+)-catéchine et l'épiafzélechine en tant qu'unités d'extension. Les polysaccharides de la paroi cellulaire ont montré une stabilité moyenne après la transformation et le stockage, avec seulement une diminution marquée du degré de méthylation des pectines. Les méthodes TT et OH ont permis de mieux préserver la couleur après un stockage de 60 jours, tandis que les méthodes non thermiques HPP et PEF ont entraîné une dégradation plus élevée de la couleur, probablement en raison d’une inactivation partielle des enzymes. Les interactions entre les pectines et les anthocyanes étaient faibles et n'ont pas influencé de manière significative l'hydratation de l’ion flavilium des anthocyanes. Une faible protection contre la perte de couleur réversible par hydratation a pu être mise en évidence avec les PAC qui contenaient à la fois des unités de procyanidines et de propélargonidines. Cependant, les proanthocyanidines ont eu un impact négatif sur la stabilité des anthocyanes au cours du traitement thermique. Ainsi, la stabilité de la couleur des nectars de fraises est principalement due à la teneur élevée en anthocyanes de certaines variétés, mais aussi aux conditions de traitement, en particulier les traitements TT et OH, qui conduisent à une plus grande stabilité de la couleur. Cette recherche offre des perspectives essentielles pour améliorer la qualité des boissons à base de fruits.Strawberry nectar is a popular fruit-based product, but maintaining its colour stability after processing and storage remains a challenge. The main objective of this thesis was to explore the parameters involved in the colour stability of strawberry nectar such as cultivar, ripening stage, harvest date, processing conditions and storage time. Moreover, to better understand the mechanism of colour stability of strawberry anthocyanins, hydration of the red flavylium ion and thermal autoxidation were studied in model system at pH 3.6, in the presence of different proanthocyanidin (PACs) and pectin fractions. As expected, both phenolic compounds and polysaccharide compositions depend on cultivar, ripening stage and harvest date. Ripening and late harvest increased anthocyanin contents and reduced PACs contents whereas changes in other polyphenols were minor. Ripening and late harvest increased the loss of pectin side chains. The great nectar colour stability was observed for overripe samples from late harvest. Nectar colour stability was correlated in strawberry with a high content in anthocyanins, a low PACs contents, and with pectins rich in galactose. The effects of different processing methods on phenolic compounds, cell wall and colour stability were assessed comparing thermal treatment (TT), high-pressure processing (HPP), and pulsed electric field (PEF), on colour stability. Proanthocyanidins and anthocyanins remained the main phenolic classes after processing, although storage led to decrease of their contents, especially after PEF. Proanthocyanidin constitutive units were significantly affected by processing and storage, particularly (+)-catechin and epiafzelechin as extension units. Cell wall polysaccharides exhibited fair stability after processing and storage, with only marked decrease in pectins’ degree of methylation. TT and OH best-preserved colour during 60-day storage, while non-thermal methods HPP and PEF resulted in greater colour degradation probably due to partial enzyme inactivation. Interactions between pectins and anthocyanins were weak and did not significantly influence hydratation of the red flavilium. A weak protection against the reversible colour loss by hydration could be evidenced with PACs which contained both procyanidins and propelargonidin units. However, proanthocyanidins negatively impacted anthocyanins stability during thermal treatment. Hence, colour stability in strawberry nectars is mostly driven by the high anthocyanin content of specific varieties but also to processing conditions, TT and OH leading to higher colour stability. This research offers critical insights to improve quality of fruit-based beverages and their long-term shelf life
Processing apple purees under vacuum to limit the loss of health-promoting compounds (ProOrg Practice Abstract)
No full textThis ProOrg Practice Abstract recommends cooking under vacuum, which limits the use of additives while maintaining the nutritional and organoleptic properties of organic fresh fruits. Using a microwave cooker is faster than conventional cooking. Recommendations are moreover provided for improving the organoleptic properties and nutritive quality of processed fruit
Interactions with other macromolecules
No full textInternational audienceThe bioactive activities of the phlorotannins depend not only on their structure, composition, conformation, and quantity but also on their intermolecular interactions. Hence, phlorotannins like terrestrial tannins interact with macromolecules, i.e., proteins and polysaccharides. This chapter summarizes the current state of knowledge on both the internal and external factors that influence phlorotannins macromolecules interactions, and introduces the different mechanisms involved in these interactions
Interactions between polyphenols and polysaccharides: Mechanisms and consequences in food processing and digestion
No full textBackground: Interactions between intracellular polyphenols and plant cell-walls have received little attention, due to analytical limitations. It was difficult until recently to analyse the most implicated polyphenols, which are proanthocyanidins (aka condensed tannins), and because these weak interactions were too low for quantification. They are becoming recognized as a factor to understand extractability, functional and health effects of polyphenols.
Scope and approach: New approaches that have been used since the turn of the century are binding
isotherms and isothermal titration calorimetry. They allow to investigate specifically these interactions, quantify the affinities between cell-walls and polyphenols as well as the impact of fruit maturation or processing, and the consequences on the finished beverages and food. This review will highlight results on this topic since 2001.
Key findings and conclusions: The most common polyphenols are phenolic acids and oligo or polymeric
flavanols (proanthocyanidins), located inside the vacuole in intact plant cells. The proanthocyanidins bind spontaneously to the plant cell-wall polysaccharides through plant tissue disruption, for example during grinding, mastication or thermal treatments, etc. The highest affinity is observed with pectins, which may help explain some of the effects of maturation on polyphenol extractability, e.g. in wine making. Presence of proanthocyanidins together with the cell-walls in the lower gut further impacts on the production of colonic metabolites. This has profound consequences on the extractability and bioavailability of the polyphenols, on the functional characteristics of extracted polysaccharides, and on the fermentation kinetics of dietary fibers and polyphenols
Association entre les procyanidols et les polymères pariétaux de pommes (quantification et conséquences)
No full textLes associations procyanidols/paroi ont été quantifiées en mettant en contact une solution procyanidolique et une suspension pariétale. La quantité de procyanidols associés à la paroi augmente avec le degré de polymérisation, le pourcentage de galloylation et la proportion de (+)-catéchine indiquant un effet de la stéréochimie des flavan-3-ols. Les liaisons gouvernant les interactions sont de faible énergie, de type liaisons hydrogènes et interactions hydrophobes. La capacité des parois et des polyosides sous forme solide à fixer les procyanidols est fonction de leur porosité, leur structure et de leur caractère hydrophobe. Un polysaccharide poreux, formant un réseau et hydrophobe, a une affinité supérieure. Un modèle prédictif de transfert des polyphénols au jus est établi. Il permet d’expliquer 60 à 90% de la perte en procyanidols ainsi que les variations avec le degré de polymérisation. La paroi exerce donc une sélectivité lors du transfert des polyphénols des fruits aux jus.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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