<p style="text-align: justify;"><strong>Aims</strong>: The purpose of this work was to evaluate the general phenolic composition and the anthocyanin profile of 24 grape varieties from two Portuguese wine regions as well as their antioxidant activity in the different grape berry fractions (skins, pulps and seeds).</p><p style="text-align: justify;"><strong>Methods and results</strong>: Individual anthocyanin composition of grape skin extracts was analyzed by HPLC, whereas total antioxidant activity was evaluated by two methods: DPPH and ABTS. In general, a high variability was found among the different autochthonous and non-autochthonous grape varieties in relation to the polyphenolic compounds analyzed, especially the individual anthocyanins. The individual anthocyanins in grape skin extracts were mainly malvidin (1.40-7.09 mg/g of skin), in particular malvidin-3-glucoside (0.62-6.09 mg/g of skin). The highest antioxidant activity was consistently detected in the seed extracts; however, it was not possible to establish a clear difference among the grape varieties analyzed.</p><p style="text-align: justify;"><strong>Conclusion</strong>: High variability in polyphenolic content, individual anthocyanin composition and antioxidant activity was found among the diverse autochthonous and non-autochthonous grape varieties studied. Seeds showed the highest antioxidant activity, followed by skin and pulp, irrespective of the grape variety.</p><p style="text-align: justify;"><strong>Significance</strong><strong> and impact of the study</strong>: Most vineyards in Portugal grow Portuguese cultivars of <em>Vitis Vinifera</em> L. and other cultivars grown worldwide. The phenolic compounds and antioxidant activity of these grape cultivars have never been characterized under the environmental conditions of the <em>Douro </em>and <em>Dão </em>regions. The variability in phenolic content among the grape varieties studied confirms the hypothesis that genetic factors have an important role in the biosynthesis of these compounds and, consequently, in the antioxidant activity of grapes.</p>

No abstract

No abstract

The wines used in this study constitute quite a heterogeneous group, made from different Portuguese red grape varieties, with diverse ages and two ageing processes (bottle and oak wood barrels); and accordingly, they showed important differences, especially in their phenolic composition. Finally, the oak wood ageing process before bottling had a negative effect in individual anthocyanins content in contrast to matured red wines submitted only to a bottle ageing process.

In this work, the effect of pre-fermentative skin maceration (PFSM) on the chemical composition of the macromolecular fraction, polysaccharides and proteins, phenolic compounds, chromatic characteristics, and protein stability of Albariño monovarietal white wines was studied. PFSM increased the extraction of phenolic compounds and polysaccharides and reduced the extraction of pathogenesis-related proteins (PRPs). PFSM wine showed significantly higher protein instability. Sodium and calcium bentonites were used for protein stabilisation of wines obtained with PFSM (+PFSM) and without PFSM (-PFSM), and their efficiencies compared to fungal chitosan (FCH) and k-carrageenan. k-Carrageenan reduced the content of PRPs and the protein instability in both wines, and it was more efficient than sodium and calcium bentonites. FCH was unable to heat stabilise both wines, and PRPs levels remained unaltered. On the other hand, FCH decreased the levels of wine polysaccharides by 60%. Sodium and calcium bentonite also decreased the levels of wine polysaccharides although to a lower extent (16% to 59%). k-Carrageenan did not affect the wine polysaccharide levels. Overall, k-carrageenan is suitable for white wine protein stabilisation, having a more desirable impact on the wine macromolecular fraction than the other fining agents, reducing the levels of the wine PRPs without impacting polysaccharide composition.