This paper investigates the potential of the enzymatic management of high pH in white juice and wine using a combination of enzymes-glucose oxidase coupled with catalase. Catazyme^® 25 L, a commercially available blend of the two enzymes, was added at different doses (0.2 g/L, 0.6 g/L, and 1g/L) to white grape juice and various parameters (glucose, gluconic acid, pH) were monitored over 24 h of treatment. Treated wines were fermented to dryness without any difficulty and the wines were chemically and sensorially evaluated. At the highest dose (1 g/L), pH was reduced from 3.9 to 3.2, with 20.5 g of gluconic acid produced, while at the lowest dose (0.2 g/L), pH decreased from 4.0 to 3.5 and 8.8 g of gluconic acid was produced. Flash profiling indicated that treated wines were lighter in color than the control and were described using terms such as floral, fruit, citrus, and sour while the control wine was described as being fermented, medicinal, pungent, and oxidized. In conclusion, glucose oxidase coupled with catalase was shown to be effective at significantly reducing juice and wine pH in a short amount of time and with a positive impact on the organoleptic profiles of the treated wines.

Ladybug taint (also known as ladybird taint) is a relatively recently recognized fault that has been identified in wines from a wide range of terroirs. Alkyl-methoxypyrazines—particularly 2-isopropyl-3-methoxypyrazine—have been determined as the causal compounds, and these are introduced into grape must during processing, when specific species of vineyard-dwelling Coccinellidae are incorporated into the harvested fruit. Coccinella septempunctata, and especially the invasive Harmonia axyridis, are the beetles implicated, and climate change is facilitating wider dispersal and survivability of H. axyridis in viticultural regions worldwide. Affected wines are typically characterized as possessing excessively green, bell pepper-, and peanut-like aroma and flavor. In this paper, we review a range of vineyard practices that seek to reduce Coccinellidae densities, as well as both “standard” and novel wine treatments aimed at reducing alkyl-methoxypyrazine load. We conclude that while prevention of ladybug taint is preferable, there are several winery interventions that can remediate the quality of wine affected by this taint, although they vary in their relative efficacy and specificity.

Background and goals High grape pH directly influences the quality of the subsequent wines. Acidulation of grape juice and grape must by tartaric acid is a common practice but can leave a wine’s flavor unbalanced. Commercially available Catazyme® 25L, which contains the enzymes Glucose Oxidase (GOx) and Catalase, was investigated as a valid way to lower high pH in red grape juice/must while simultaneously lowering glucose, lowering potential alcohol, and increasing acidity. Methods and key findings Tempranillo must and juice were treated with Catazyme® 25L at two levels of dosage (0.5 g/L and 1g/L) over a 24 hrs period under continuous aeration. Chemical and sensory analyses were performed on the resulting wines. Results indicated that the pH of Tempranillo juice was lowered by 0.84 units when using Catazyme® 25L at a rate of 1.0g/L. Similarly, addition of Catazyme® 25L at 0.5g/L decreased pH from must and juice, from 4.6 to 4.0 and 3.8, respectively. Lower alcohol wines were produced when using Catazyme® 25 L due to glucose being converted into gluconic acid. Sensory evaluation of the wines indicated a positive impact of the enzyme on color, aroma, and in-mouth flavor. Conclusions and significance GOx in conjunction with catalase is an effective pH management system and of particular value in hot climate winemaking, where it can also help lower alcohol concentration, while positively impacting the sensory profiles of the wines.

Alkyl-methoxypyrazines are an important class of odor-active molecules that contribute green, ‘unripe’ characters to wine and are considered undesirable in most wine styles. They are naturally occurring grape metabolites in many cultivars, but can also be derived from some Coccinellidae species when these ‘ladybugs’ are inadvertently introduced into the must during harvesting operations. The projected impacts of climate change are discussed, and we conclude that these include an altered alkyl-methoxypyrazine composition in grapes and wines in many wine regions. Thus, a careful consideration of how to manage them in both the vineyard and winery is important and timely. This review brings together the relevant literatures on viticultural and oenological interventions aimed at mitigating alkyl-methoxypyrazine loads, and makes recommendations on their management with an aim to maintaining wine quality under a changing and challenging climate.

This review examines the impact of cluster thinning (CT) on wine quality. CT is a vineyard management technique intended to enhance the sensory attributes of wine, such as aroma and flavour. We employed a narrative approach, synthesising findings from various studies without the use of statistical meta-analysis. This method allowed us to capture a broad spectrum of insights and draw practical conclusions for winemakers. Our review spans different grape varieties and climates. The studies reviewed include CT interventions at various growth stages—flowering, fruit set, veraison, and post-veraison—with varying levels of thinning severity. Methods range from manual thinning to mechanical approaches, with comparisons made to control groups that did not undergo CT. Our primary focus was on sensory analysis, wine phenolic composition volatile compound composition, and overall quality assessments. We paid particular attention to sensory descriptors related to aroma and flavour profiles, evaluating quality and preference scores. This review consolidates existing research to provide a comprehensive understanding of CT's role in viticulture. It offers practical guidance for optimising CT practices to improve wine quality and identifies areas where further research is needed. By integrating diverse findings, this review contributes valuable insights for winemakers aiming to enhance their vineyard management techniques.

This study assessed the economic viability of producing verjus (“green juice”) from cluster-thinned grapes. Utilizing the Delphi Method and insights from an expert panel, a comprehensive partial budget model was constructed for vineyards and wineries, focusing on the financial impact of verjus production. Existing vineyards with cluster thinning practices benefited from verjus production. However, vineyards considering cluster thinning solely for verjus may face lower profit margins without a substantial increase in grape harvest prices. Winery operations were also examined, comparing costs of using verjus as an acidifying agent for wine and producing it as a bottled product. Verjus was relatively more expensive than tartaric acid for acidification, but added volume could offset the cost, making it desirable. Additionally, as a standalone product, verjus showed promising profitability, presenting an opportunity for wineries to explore this niche market and expand product offerings. In conclusion, existing vineyards could benefit from verjus production, while wineries could consider using verjus as an acidifying agent or explore its use as an individual product. Careful consideration of costs and market demand is crucial for informed decisions regarding verjus production.