No abstract

The anthocyanin composition was analysed in strawberry fruits from five different cultivars (cv. Eris, Oso Grande, Carisma, Tudnew and Camarosa). Twenty-five defined anthocyanin pigments were detected, most of them containing Pelargonidin (Pg) as aglycone; some cyanidin (Cy) derivatives were also found. Glucose and rutinose were the usual substituting sugars, although arabinose and rhamnose were also tentatively identified; some minor anthocyanins showed acylation with aliphatic acids. A relevant aspect was the detection of anthocyanin-derived pigments, namely 5-carboxypyranopelargonidin-3-glucoside and four condensed pigments containing C-C linked anthocyanin (Pg) and flavanol (catechin and afzelechin) residues. Total anthocyanin content ranged between 200 and 600 mg kg À1 , with Pg 3-gluc constituting 77-90% of the anthocyanins in the strawberry extracts followed by Pg 3-rut (6-11%) and Cy 3-gluc (3-10%). A notable variability was found among the anthocyanin concentrations in samples of a same variety and harvest, indicating a strongly influence of the degree of maturity, edaphic-climatic factors and post-harvest storage.

The flavanol composition of the seeds of 17 varieties of grape cultivated in the main wine-producing areas of Castilla-Leon (Spain) was studied. Twenty-seven different flavan-3-01s of procyanidin type were found, but no prodelphinidins were detected. Minor amounts of four hydrolyzable tannins were also present in the seed extracts of most of the grapes analyzed. All the varieties contained galloyled flavanols, such that their presence could be considered characteristic of the grape seed composition. Some proposals concerning the biosynthesis of flavan-3-01 in the grape seed are also advanced taking into account the compounds

An HPLC method using a normal-phase silica column and a gradient of dichloromethane-methanol-formic acid-water mixtures as the eluent was developed to separate procyanidins on a molecular mass basis, without derivatization. It was successfully applied to the analysis of procyanidin extracts from cacao beans and grape seeds. The monomers and major dimers were resolved as discrete peaks. Oligomeric and polymeric components were eluted in order of increasing degree of polymerization, as confirmed by determining the average molecular mass of successive fractions collected from the normal-phase column using gel permeation chromatography, after acetylation.

Mouthfeel characteristics of wine phenolic compounds (catechin, epicatechin, coumaric acid, caffeic acid, protocatechuic acid and gallic acid) were evaluated by sensory analysis using a Labeled Magnitude Scale for rating the intensity of the perceived sensations. Synergisms on bitterness and on astringent sub-qualities were detected when the phenolic compounds were tested as mixtures in comparison to individual compounds, maintaining the total amount of stimulus constant in all tasted samples. Principal component analysis was applied to observe trends in the data and to indicate relationships between phenolic substances and sensory attributes. It allowed us to easily visualize the synergistic effect discussed above. To our knowledge, this is the first time that astringency synergism between phenolic compounds has been described. This research also shows that wine aromas may modulate the perception of the astringency. In this study, the addition of volatile compounds increased the intensity of the astringent perception of the flavanol solutions and also its persistence.