Effect of Microwave Maceration and SO2 Free Vinification on Volatile Composition of Red Wines

The technology of high-power ultrasound and its effect on the color and aroma of rosé wines

BACKGROUND

The application of high-power ultrasound (US) has been studied extensively to obtain value-added red wines using short maceration times. It is a technique of wide interest for the extraction of aromatic compounds and compounds responsible for color, so it could also be an important tool to use in the elaboration process of rosé wines. Thus, this study focused on the effect of the application of US on the phenolic, aromatic, and sensorial profile of rosé wines. For this, three different types of rosé wine were produced: a control with direct pressing after crushing, another wine obtained from a 4 h macerated must, and a wine whose crushed and destemmed grape was sonicated and subsequently pressed.

RESULTS

The results showed a higher color intensity and a higher total polyphenol and anthocyanin content in the wine obtained from sonicated grape compared to both control wine and that obtained from grape macerated for 4 h. Ultrasound treatment enhanced the extraction of varietal volatile compounds in must, especially the free faction of terpenes and norisoprenoids. It also gave rise to wines with a higher concentration of C6 alcohols and other compounds such as guaiacol and 4-vinylguaiacol, but led to fewer fatty acids, especially C6, C4 and C8 acids. Sensorially these wines showed intense aromas of red fruits and flowers, while no defects in aroma or astringency were found.

CONCLUSIONS

The color and sensory profile of the resulting wines indicate that the US may be an interesting tool for obtaining quality rosé wines, replacing the maceration stage and reducing potential oxidation problems. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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.

Power ultrasound treatment of Viognier grapes as a tool to increase the aromatic potential of wines

BACKGROUND

High-power ultrasound is a novel and non-thermal technique normally used in red vinification to increase the extraction of phenolic compounds. However, few studies have been carried out on its effect on the extraction of aroma compounds and their precursors in white grapes. This study evaluates the effect of high-power ultrasound at winery scale in the maceration of Viognier grapes on the content of varietal volatile compounds (free and glycosidically bound) in musts and wines, in comparison with wines from direct pressing and from short skin maceration.

RESULTS

The pre-fermentative ultrasound treatment of the grapes produced an increase in most of the varietal compounds of musts and wines, both in the free fraction and in the bound one, especially in the C6 alcohols, terpenes and norisoprenoids, some of them of sensory relevance, while the effect on esters and lactones was less evident. Ultrasound maceration allowed us to obtain wines of higher aromatic intensity, with a more pronounced varietal character.

CONCLUSION

The pre-fermentative ultrasound treatment of Viognier grapes increases the aromatic potential of the wines, as it favors the extraction of free and bound varietal volatile compounds. In addition, it allows the maceration time of the grapes to be reduced compared to conventional pre-fermentation techniques, thus avoiding oxidative processes that could negatively affect the aroma of the wines. © 2022 Society of Chemical Industry.

The Application of Non-Thermal Technologies for Wine Processing, Preservation, and Quality Enhancement

Recently, non-thermal wine processing technologies have been proposed as alternatives to conventional winemaking processes, mostly with the aims to improve wine quality, safety, and shelf-life. Winemakers typically rely on sulfites (SO2) to prevent wine oxidation and microbial spoilage, as these processes can negatively affect wine quality and aging potential. However, SO2 can trigger allergic reactions, asthma, and headaches in sensitive consumers, so limitations on their use are needed. In red winemaking, prolonged maceration on skins is required to extract enough phenolic compounds from the wine, which is time-consuming. Consequently, the wine industry is looking for new ways to lower SO2 levels, shorten maceration times, and extend shelf life while retaining wine quality. This review aggregates the information about the novel processing techniques proposed for winemaking, such as high-pressure processing, pulsed electric field, ultrasound, microwave, and irradiation. In general, non-thermal processing techniques have been shown to lead to improvements in wine color characteristics (phenolic and anthocyanin content), wine stability, and wine sensory properties while reducing the need for SO2 additions, shortening the maceration time, and lowering the microbial load, thereby improving the overall quality, safety, and shelf life of the wines.

Current Technologies to Accelerate the Aging Process of Alcoholic Beverages: A Review

The aging process contributes to the sensory evolution of alcoholic beverages, producing changes in the color and flavor of the final product. Traditionally, aging has occurred by storing beverages in wooden barrels for several months or years. To meet the demand for aged beverages, there is a need for large storage areas, a large number of wooden barrels, and, consequently, large volumes of stored product. Evaporation losses can also occur. In addition to the reactions of the beverage itself, there is also a transfer of wood compounds to the drink, which is later modified by successive oxidation reactions. This study addresses the alternative methods for accelerating the aging stage of beverages. These include the use of wood fragments, ultrasound, micro-oxygenation, pulsed electric field, high hydrostatic pressure, and microwave and gamma irradiation. These methods can be applied to optimize the process of extracting wood compounds, promote free radical formation, reduce oxidation reaction time, and accelerate yeast autolysis time. This study provides examples of some of the aforementioned methods. These technologies add value to the aging process, since they contribute to the reduction of production costs and, consequently, can increase commercial competitiveness.

Use of Microwave Maceration in Red Winemaking: Effect on Fermentation and Chemical Composition of Red Wines

The objective of this study was to evaluate the effect of microwave treatment of crushed grapes on the yeast population of the must and on the development of alcoholic fermentation, as well as on the extraction of different compounds from the grapes such as polysaccharides and amino acids that can affect the organoleptic quality and stability of the wine. This study demonstrated for the first time the effect of the microwave treatment of grapes on native yeast species and their diversity, producing an increase in fermentation kinetics and a decrease in the lag phase. The microwave treatment produced a positive effect on the extraction of amino acids and polysaccharides from the grapes, resulting in significantly higher amounts of the main amino acids of the must and some major volatile compounds in the treated samples. The polysaccharides most affected by the microwave treatment were the PRAGs, the main polysaccharides liberated from grapes during the maceration.