Substitution or Dilution? Assessing Pre-fermentative Water Implementation to Produce Lower Alcohol Shiraz Wines

Yeast or water: producing wine with lower alcohol levels in a warming climate: a review

Climate change effects over the last century have seen grape wine growers being faced with earlier budburst and shorter seasons. One effect is higher sugar levels in the grape berries, resulting in wines with higher than typical alcohol concentrations. Winemakers, both in Australia and globally, need to reassess their wine making approaches to address the challenges associated with warmer drier conditions. This review focuses on two pre-fermentation approaches that address ethanol production during fermentation, so that wine makers can produce a wine with lower final alcohol levels at the same time as addressing any negative impacts on wine quality. First, microbiological yeast approaches are reviewed. This approach can reduce final alcohol levels in a treated wine between 0.2% v/v-3.7% v/v; however, diverse wine quality impacts can result, dependant on the microbiological yeast approach taken. Second, the pre-fermentation approach of water addition/substitution into a high sugar grape must is reviewed. To date, recent studies indicate that this 'water treatment' of musts approach is effective with respect to reducing final alcohol levels from between 0.6% v/v-5.9% v/v in the resultant wines, with less variation effects on final wine quality. It is noted that further studies for the 'water treatment' of high sugar musts approach are required to provide additional foundational data sets with respect to impacts on chemical, phenolic and sensory attributes of the final wine products, both within and across vintages. This is especially important as winemakers adapt their winemaking approaches in a changing climate. © 2022 Society of Chemical Industry.

Evaluation of bio-acidifying yeast Lachancea thermotolerans as a strategy to reduce the effects of climate change in Tempranillo grape must vinification

The effects of climate change are posing major challenges for winemaking, especially in warm regions. Rising temperatures are leading to a considerable increase in sugar content and a reduction in the acidity of grape juices. This has prompted the search for new chemical and biological tools to reduce these effects in winemaking. Lachancea thermotolerans represent an interesting tool for wine improvement, due to their effects on lactic acid, ethanol, and volatile acidity. In this study, we evaluated the sequential inoculation of Lachancea thermotolerans (AEB Italia) + Saccharomyces cerevisiae as an alternative to the addition of water and tartaric acid in the vinification of over-ripened wine must (Tempranillo cv.). To do so, we conducted a micro vinification experiment that included three experimental treatments (replicated four times); AAS = Addition of water + tartaric acid fermented with Saccharomyces cerevisiae, ALS = sequential fermentation with Lachancea thermotolerans followed by Saccharomyces cerevisiae and SAC = Only inoculation with Saccharomyces cerevisiae (control). We measured the lactic acid, malic acid, acetic acid, total acidity, pH, glucose + fructose, and ethanol concentration of the resulting wines. We found a higher lactic acid content and total acidity in ALS wines (2.2 g/L y 6.65 g/L) compared with AAS (0.13 g/L y 5.75 g/L) and SAC wines (0.18 g/L y 5.37 g/L). ALS wines showed a significantly lower pH (4.00) than SAC wines (4.19) but did not differ significantly from AAS wines (3.19). Finally, acetic acid was higher in ALS wines (0.89 g/L) than AAS wines (0.64 g/L) but did not differ significantly from SAC wines (1.02 g/L). Our results point out that the use of Lachancea thermotolerans in a sequential inoculation with Saccharomyces cerevisiae is an alternative to the addition of water and tartaric acid in the vinification of over-ripened Tempranillo musts.

Techniques for Dealcoholization of Wines: Their Impact on Wine Phenolic Composition, Volatile Composition, and Sensory Characteristics

The attention of some winemakers and researchers over the past years has been drawn towards the partial or total dealcoholization of wines and alcoholic beverages due to trends in wine styles, and the effect of climate change on wine alcohol content. To achieve this, different techniques have been used at the various stages of winemaking, among which the physical dealcoholization techniques, particularly membrane separation (nanofiltration, reverse osmosis, evaporative perstraction, and pervaporation) and thermal distillation (vacuum distillation and spinning cone column), have shown promising results and hence are being used for commercial production. However, the removal of alcohol by these techniques can cause changes in color and losses of desirable volatile aroma compounds, which can subsequently affect the sensory quality and acceptability of the wine by consumers. Aside from the removal of ethanol, other factors such as the ethanol concentration, the kind of alcohol removal technique, the retention properties of the wine non-volatile matrix, and the chemical-physical properties of the aroma compounds can influence changes in the wine sensory quality during dealcoholization. This review highlights and summarizes some of the techniques for wine dealcoholization and their impact on wine quality to help winemakers in choosing the best technique to limit adverse effects in dealcoholized wines and to help meet the needs and acceptance among different targeted consumers such as younger people, pregnant women, drivers, and teetotalers.

Pre-Fermentation Water Addition to High-Sugar Shiraz Must: Effects on Wine Composition and Sensory Properties

Changes to Australian regulations now allow the limited addition of water to high-sugar musts pre-fermentation. In light of these changes, this study explored how water addition affects Shiraz wine composition and sensory properties. Wines were made from grapes at ≈13.5, 14.5 and 15.5° Baume. Water was added to musts from the ripest fruit by direct addition, or by using a juice substitution (run-off and replace) approach. To compare the effect of juice run-off independently, saigneé treatments were included. Wines made from the fruit that was harvested earlier generally had a lower “opacity” and higher “red fruit” aroma as the defining sensory attributes. Undiluted wines made from riper fruit had higher phenolics, and were characterised by “dark fruit” and “dried fruit” attributes, and “spice”, a “brown colour” and “opacity”. These attributes were accentuated in wines from the same fruit which received saigneé treatments and reduced in all of the water addition treatments. In particular, higher levels of water addition without juice substitution increased the “cooked vegetable” and “drain” attributes in the wines. This indicates possible negative effects of larger water additions, such that a low to moderate adjustment in Shiraz winemaking is suggested.