A Semillon wine was bottled using 14 different closures: a screw‐cap type, two grades of conventional natural cork, two ‘technical cork’ closures (natural cork with a synthetic component), and 9 closures manufactured from synthetic polymer material. Closure performance was evaluated for physical aspects (e.g. extraction force and energy, change in closure diameter, and ease of closure reinsertion), and for wine composition and sensory properties. Wine under the screw cap closure retained the greatest concentration of sulfur dioxide (SO2) and ascorbic acid and had the slowest rate of browning. For other closures the trend of SO2 loss relative to the screw cap closure was apparent from an early stage of testing, and was most evident in the group of synthetic closures, intermediate in the conventional corks, and least evident in the technical cork closures. The loss of SO2 was in general highly correlated with an increase in wine browning (OD420) and the concentration of SO2 in the wine at six months was a strong predictor of future browning in the wine, particularly after eighteen months. Neither the concentration of dissolved oxygen at bottling (0.6–3.1 mg/L), nor the physical closure measures were predictors of future browning. For several closures upright storage tended to accelerate loss of SO2 from the wine, but in many cases this effect was marginal. The closures differed widely in regard to physical characteristics, and in general synthetic corks appeared least ‘consumer‐friendly’ in terms of extraction forces, energies, and ease of closure re‐insertion, but there was a trend for natural cork closures to exhibit larger variability in physical characteristics than technical cork and synthetic closures. Sensory analysis indicated large differences in wine flavour properties, with closures which tended to result in the best retention of free SO2 having wine sensory scores for ‘citrus’ that were generally high whilst scores for the attributes ‘developed’/‘oxidised’ were low. The situation was reversed for wine under closures that performed poorly in the retention of free SO2. It was found that below a critical level of free SO2 remaining in the wine, closures exhibited substantially higher ‘oxidised’ aroma. Whilst trichloroanisole‐type (TCA) taint was a noticeable problem for some cork and technical cork closures, any plastic‐type taint appeared not to be a problem with most synthetic closures.

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Background and Aims An elevated concentration of several volatile phenols and their glycosides in grapes and wines is associated with exposure of grapes to forest fire smoke. Interpretation of phenol compositional data from grapes or wines, however, is complicated by the fact that traces of these compounds can be detected in non‐smoke‐exposed samples. Hence, the concentration of smoke marker compounds was investigated with the aim of providing a reference data set to help determine smoke exposure. Methods and Results Thirteen phenolic compounds were measured in non‐smoke‐exposed grape berries and unoaked wines made from 12 cultivars collected from multiple regions across Australia over four vintages. The grapes and wines contained a low concentration of several volatile phenols and their glycosides. These varied in concentration between cultivars but showed little variation between regions and vintages. The maximum concentration observed for any analyte was below 15 μg/kg in grapes and approximately 15 μg/L in wine. Conclusions The results for smoke marker compounds should be considered on a per‐cultivar basis when determining smoke exposure. Interpretation of results for a potentially smoke‐exposed sample can be achieved based on comparison with the 99th percentile values reported here. Use of the interpretation system described should be limited to determining smoke exposure and not smoke taint. Significance of the Study This study provides a comprehensive set of data that defines the upper limits of smoke marker compounds expected in Australian grapes and wines from non‐smoke‐exposed vineyards that can be used for determining the likelihood of smoke exposure.

Supersaturation of wine with dissolved tartaric acid is an essential requirement for crystallisation of potassium bitartrate and can be thought of as the driving force. Nucleation must occur, however, before potassium bitartrate crystals can grow and precipitate out of solution. In recent years, wine additives capable of inhibiting potassium bitartrate crystallisation have been commercially available. In this review, the established mechanisms involved in crystallisation are discussed, as they are essential for correctly interpreting the inhibitory effect that wine colloids and additives, such as mannoproteins and carboxymethylcellulose, can have upon potassium bitartrate crystal growth. The wine additive carboxymethylcellulose, in particular, is discussed in detail, as this additive is being trialled increasingly by winemakers since its approval for winemaking.

Wine grapes exposed to smoke and wine made from grapes exposed to smoke can robustly be identified through their elevated concentrations of volatile phenols and phenolic glycosides serving as smoke markers, compared to concentrations typically found in non-smoke-exposed samples. Smoke-affected wines with high concentrations of volatile phenols and glycosides can have smoky flavours, but the relationship between concentrations of specific smoke markers in grapes and the intensity of smoky sensory attributes in the resulting wine has not been established. This study sought to determine whether volatile phenols and glycoside concentration in grapes and wine are suited to predict smoke flavour, to identify the key drivers of smoke flavour in both matrices. The study aimed to determine what concentrations of volatiles and glycosides in grapes impart an unacceptable smoke flavour in the resulting wine, to provide a guide for producers assessing suitability of smoke-exposed grapes for wine production. During vintage 2020, a total of 65 grape samples were collected from vineyards exposed to bushfire smoke, as well as unaffected vineyards. Chardonnay, Pinot Noir, and Shiraz grapes were harvested from vineyards in New South Wales, South Australia, and Victoria. Unoaked wines (50 kg scale) were produced under controlled conditions. The wines had a wide range of smoke flavour intensities rated by a trained sensory panel. Statistical models based on guaiacol, o-cresol, m-cresol, p-cresol, and some glycosides gave good predictions of smoke flavour intensity, with a slightly different optimal model for each cultivar. Subsequently, critical concentrations for quality defects were estimated to provide a guide for producers. A subset of smoke exposure markers in wine grapes affected by smoke from bushfires can be used to predict the degree of smoke flavour in wine. This information provides a first guide for assessing the risk of producing smoke tainted wine from smoke-exposed grapes.