Microwave irradiation: impacts on physicochemical properties of red wine

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.

Chemical and Sensory Characteristics of Different Red Grapes Grown in Xinjiang, China: Insights into Wines Composition

Globally, the red wine market experienced a rapid growth in the last decade, due to the superior colour, taste, and nutritional quality. The red grapes used for vinification have individual characteristics varying within the regional environment. In this study, the quality of seven grape cultivars, including Marselan, Yan 73, Muscat Hamburg, Kadarka, Merlot, Cabernet Sauvignon, and Crimpose, and their corresponding wines, were investigated based on high-performance liquid chromatography and headspace solid-phase microextraction coupled to gas chromatography–mass spectrometry. These techniques were performed to analyze the chemical compositions and volatile compounds of the tested samples, respectively. The results showed that tartaric acid (29.96% to 73.45%) and rutin (12.53% to 56.54%) were the dominant organic acid and phenolic compounds in grapes, respectively. Higher concentrations of organic acids and phenolic compounds, and the types of volatile compounds, were observed to be highest in the Cabernet Sauvignon grape. The antioxidant activity of wines ranged from 6.74 to 102.68 mmol TE/L, and Yan 73 wine had the highest antioxidant activity. A total of 69 volatile compounds consisting of 17 alcohols, 26 esters, 5 aldehydes, 9 acids, 7 ketones, and 5 other volatile compounds were identified in all tested wines, and 11 important aroma active substances (odor activity value > 1) were selected, consisting of β-ionone, phenethyl acetate, geranyl acetate, ethyl 9-decenoate, ethyl caprate, ethyl pelargonate, decanal, ethyl caprylate, 6-methyl-5-hepten-2-one, methyl 2-hexenoate, and ethyl hexanoate, which endow wines with a unique aroma. This work clearly describes the chemical and sensory characteristics of seven red grape cultivars in Xinjiang of China and provides diversity options for cultivars for winemaking.

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.

Microwave Irradiation: Effects on the Change of Colour Characteristics and Main Phenolic Compounds of Cabernet Gernischt Dry Red Wine during Storage

Wine colour is an essential organoleptic property considered by consumers. In this paper, the potential effects on colour characteristics and the content of main phenolic compounds in red wine under microwave irradiation were investigated during wine storage. The results showed that the changing trend of colour characteristics of microwave-treated and untreated wines was very similar. Moreover, total phenolic compounds, total monomeric anthocyanins, main anthocyanins, main flavonoids, and main phenolic acids (gallic acid; caffeic acid; syringic acid; (+)-catechin; Cy-3-glu; Mv-3-glu) also showed similar change trends during storage. In other words, microwave irradiation had a long-term effect on the colour properties and main phenolic compounds of red wine, changes that require long-time aging in traditional processing. In terms of the studied parameters, the changes in microwave-treated wine were faster than those in untreated wine. These results showed that microwave technology, as a promising artificial aging technology, could in a short time produce red wine of similar quality to traditional aging.

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.