Ultrasound and microwave techniques for assisting ageing on lees of red wines

Ageing on lees is a slow process that carries microbiological and economic risks in the wineries. This study evaluates the possibility of enhancing the extraction of different compounds from the lees, using combined strategies, such as ultrasound (US) or microwaves (MW) and the addition of inactive dry yeasts (IDY), to reduce the lees ageing time. The complete chemical analysis of the wine was done, amino acids, polysaccharides, colour and volatile compounds, together with the sensory analysis. The combined treatments increased the release of total polysaccharides, mannoproteins and total monosaccharides in the wines, and some amino acids like proline. However, wines treated with US and MW, with and without lees, showed a decrease in tannins and colour intensity, and in some volatile compounds like fatty acid esters, acetates and terpenes. The wines treated with IDY and MW were the best valued for their floral and red berry flavours and less astringency.

Influence of seaweed foliar application to Tempranillo grapevines on grape and wine phenolic compounds over two vintages

The study of seaweeds is increasing in viticulture due to their implications on plant protection and grape quality. This trial aimed to study the effects of foliar applications of an Ascophyllum nodosum extract at low (0.25%, v v-1) and high (0.50%, v v-1) dosages on grape and wine phenolic compounds in 2017 and 2018. In grapes, seaweed biostimulation increased the content of malvidin-3-glc, myricetin-3-glc and myricetin-3-gal in 2017 season. Moreover, both treatments improved the synthesis of trans-piceid and total stilbenes in both seasons. Sensory analysis revealed that 2017 wines had more color than the 2018 wines, which coincided with color intensity parameters. Therefore, seaweed applications to grapevines improved stilbenes content in grapes independently of the season and its effects on the rest of phenolic compounds in grapes and wines depended strongly of season factor.

Relation between Fatty Acid Content and Its Evolution during Fermentation and Utilization of Free Amino Acids in Vacuum-Filtered Viura Must

The activity of proteins that transport amino acids changes depending on the unsaturated residue which is introduced into the phospholipids of Saccharomycescerevisiae membrane. The aim of this study was to observe the influence of fatty acid content and its evolution during fermentation on the utilization of free amino acids in Vitis vinifera var. Viura must clarified by vacuum filtration. The results demonstrate that filtration of the must did not reduce the concentration of free amino acids, but it did reduce fatty acids, especially the unsaturateds. In the first half of fermentation (up to 50% sugar consumption), fatty acid utilization was different in each sample without involving an alteration in the uptake of amino acids. In the second half of fermentation (from 50% sugar consumption until the end of fermentation), the clarified sample had greater consumption of saturated fatty acids than unsaturated, in contrast to the control; this, along with other factors, produced a greater liberation of free amino acids in the filtered sample.