The reaction between procyanidin dimer Ec-EcG (B2 3'-O-gallate) and malvidin 3-O-glucoside (Mv3glc) was studied in a model solution system at two different pH values, 2.0 and 3.8. Disappearance of both species was much faster at pH 3.8 than at pH 2.0. That of Mv3glc was increased in the presence of Ec-EcG, whereas that of Ec-EcG was the same in the presence or absence of the anthocyanin. Values of absorbance at 520 nm measured at pH 2.0 were correlated with the amount of residual Mv3glc. Those measured at pH 3.8 hardly changed during the incubation, but absorbance values at 420 and 620 nm as well as resistance to sulfite bleaching were much increased, confirming that Mv3glc was converted to other pigments. Anthocyanin-flavanol adducts were observed at both pH values, but their structures were different. At pH 2.0, cleavage of the procyanidin linkage followed by nucleophilic addition of flavanol or anthocyanin moieties led to (Ec)(n)-EcG and (Ec)(n)-Mv3glc, respectively. At pH 3.8, nucleophilic addition of Ec-EcG onto the anthocyanin yielded Mv3glc-(Ec-EcG).
Feruloylated arabinoxylans are the major non-starch polysaccharides from the cereal cell walls. Depending on the source, arabinoxylans exhibit different molecular features, which are determinants for their functional properties. Feruloylated arabinoxylans are of considerable importance in cereal process such as bread making and brewing. This polysaccharide represents a significant portion of human dietary fiber intake offering nutritional benefits as soluble and insoluble fiber. The presence of ferulic acid in arabinoxylans confers them antioxidant properties. Feruloylated arabinoxylans posses a unique capacity to form covalent gels in the presence of free radical-generating agents. The gels formed present interesting characteristics as neutral odor and taste, stability to pH and electrolyte concentration changes and a macroporous structure, which give them potential applications as matrices for controlled release in food and non-food applications. In this manuscript are reviewed the chemical structure, sources and applications of feruloylated arabinoxylans and arabinoxylan gels.
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