Abstract:The search for food products that promote health has grown over the years.

The quality of grapes, as well as wine quality, flavor, stability, and sensorial characteristics depends on the content and composition of several different groups of compounds from grapes. One of these groups of compounds are sugars and consequently the alcohol content quantified in wines after alcoholic fermentation. During grape berry ripening, sucrose transported from the leaves is accumulated in the berry vacuoles as glucose and fructose. The wine alcohol content continues to be a challenge in oenology, as it is also the study of the role of chemosensory factors in alcohol intake and consumer preferences. Several technical and scientific advances have occurred in recent years, such as identification of receptors and other important molecules involved in the transduction mechanisms of flavor. In addition, consumers know that wines with high alcohol content can causes a gustatory disequilibrium affecting wine sensory perceptions leading to unbalanced wines. Hence, the object of this review is to enhance the knowledge on wine grape sugar composition, the alcohol perception on a sensorial level, as well as several technological practices that can be applied to reduce the wine alcohol content.

<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

Cork powder, an abundant, natural, and cheap byproduct of the cork stopper industry was explored, either in its natural form or after improvement of their adsorption properties by simple physicochemical treatments, as a new sustainable wine fining agent for removing negative volatile phenols (VPs), responsible for one of the most frequent and widespread aroma defects in red wine known as “Brett character”. Cork adsorptive performance improvement by removal of cork extractives, air removal, and ethanol impregnation allowed us to obtain 41% to 62% of 4-ethylphenol (4-EP) and 50% to 53% of 4-ethylguaiacol (4-EG) removal from red wine. Performance of the optimized cork powder on removing the negative sensory phenolic defect and recovery of the positive fruity and floral sensory attributes was not significantly different from activated carbon and chitosan, two of the most efficient treatments currently available. Optimized cork powder can be a good solution for VPs removal without impacting negatively on wine quality and sensory profile and can also be used as a new sustainable enological fining agent. The developed solution for the cork powder waste produced in the cork stopper industry can increase the economic value of this abundant waste and reduce the input of new material in wine production.

<p style="text-align: justify;"><strong>Aims</strong>: Describe and compare some characteristics, such as molecular weight (MW) distribution and surface charge density of commercial protein fining agents and to enhance the understanding of their effect on wine chemical and sensory characteristics.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Protein (casein, potassium caseinate and gelatine) MW distribution was characterised by electrophoresis. These proteins were added to a red and a white wine, in order to evaluate its effect on colour, phenolic compounds and sensory attributes.</p><p style="text-align: justify;"><strong>Conclusion</strong>: A band at 30.0 kDa characterised casein and potassium caseinate. Gelatines showed polydispersion on the MW distribution, gelatine GSQ on the higher MW (&gt; 43.0 kDa) and gelatine GL on the lower MW (&lt; 43.0 kDa). Despite the fact that casein and potassium caseinate had similar MW distribution, casein decreased essentially the monomeric ((+) - catechin and (-) - epicatechin) while the potassium caseinate showed a lower influence on these compounds. Also, among the two gelatines used, a different behaviour was observed. The gelatine characterised by a polydispersion below 43.0 kDa depleted more the polymeric tannin fractions than the gelatine characterised by a polydispersion above 43.0 kDa. That gelatine has also decreased colour intensity and coloured anthocyanins of red wine but the hue remains unchanged. Addition of fining agents did not affect greatly the concentration of monomeric anthocyanins. Sensory analysis showed that wines fined with the different proteins presented distinct characteristics.</p><p style="text-align: justify;"><strong>Significance and impact of study</strong>: The knowledge of the physico-chemical characteristics, such as MW distribution and surface charge density, is important for wine fining optimisation and consequently for the wine quality.</p>

No abstract

Pinking is the term used to describe the appearance of a salmon-red blush color that may appear in bottled white wines, produced solely from white grape varieties. It is perceived as an undesirable phenomenon for both, wine consumers and winemakers. Although with seasonal and regional variations, the pinking has been observed worldwide, with predominance in white wines produced from Vitis vinifera L. grape varieties. The pinking origin of Síria white grapes has been studied in detail and it has been shown that the origin of the pinking phenomenon in white wines from Vitis vinifera L. Síria grape variety are anthocyanins, mainly malvidin-3-O-glucoside. The minimum amount of anthocyanins needed for the visualization of the wine pink color was 0.3 mg/L. Further studies in other white monovarietal wines that occasionally suffer from this defect, like white wine from Malvasia Fina grape variety, Loureiro grape variety, Sauvignon Blanc grape variety and Albariño grape variety, have shown that this wines produced from this grape varieties also show low amounts of anthocyanins, mainly malvidin-3-O-glucoside. These results show that the presence of low but visible detectable anthocyanins as the origin of the pinking phenomena is also observed in other white grape varieties besides that of Síria.