The contribution of the aldehyde composition of wine spirit to the color changes in Port red wine was studied in model solutions. Malvidin 3-glucoside was shown to be very reactive towards catechin in the presence of different aldehydes: acetaldehyde, isovaleraldehyde, benzaldehyde, propionaldehyde, isobutyraldehyde, formaldehyde, and 2-methylbutyraldehyde. LC/MS data confirmed the formation of oligomeric pigments resulting from the reaction between the anthocyanin and the flavanol (colored products) and between 2 flavanol units (colorless products) mediated by each aldehyde assayed. The UV-visible spectra of the colored pigments showed a l max bathochromically shifted relatively to the l max of original anthocyanins. All samples revealed a "blueing" and "darkening" color effects using the CIELAB system.

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The use of anthocyanins has been investigated for the preparation of food and beverage natural colorants as they seem to have nontoxic effects. In this context, vinylpyranoanthocyanins were recently found to naturally occur in ageing red wine. This new family of anthocyanin-derived pigments may be obtained directly through the reaction between anthocyanin derivatives and other compounds. Some of these newly formed pigments have been found to exhibit a bluish color at acidic pH. The formation of bluish pigment was obtained through reaction between anthocyanin-pyruvic-acid adducts and flavanols in the presence of acetaldehyde. The formation of similar bluish pigments was attempted using other different precursors. The chromatic features of this kind of pigments bring promising expectations concerning the use of these naturally occurring blue pigments in the food industry.

This review aims to highlight some aspects regarding anthocyanins bioavailability. Although there is a considerable variability in the values for the biokinetic parameters, anthocyanins appear to be rapidly absorbed and eliminated, reaching low maximal concentrations in plasma and urine. Nevertheless, some works have reported a high content of intact anthocyanins in plasma, possibly resulting from gastric absorption. So far, no anthocyanin metabolites have been detected in the stomach and the possible mechanism of anthocyanin gastric absorption is still unknown. Some progress in this field is expected to be obtained through studies involving a new human cell culture model of the gastric surface suitable for bioavailability screening of nutraceuticals like anthocyanins and anthocyanin-derived pigments. The positive health effects associated with anthocyanin consumption could derive from the contribution afforded by the stomach to intact anthocyanin absorption. Nonetheless, these latter may be further metabolized to other bioactive forms.