The release of smoke-derived volatile phenols during the fermentation of Merlot grapes, following grapevine exposure to smoke, has been investigated. The concentrations of guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-ethylphenol, and eugenol were determined by gas chromatography-mass spectrometry and found to increase throughout the winemaking process. Only trace levels (< or = 1 microg/L) of guaiacol and 4-methylguaiacol could be detected in free run juice derived from the fruit of smoked vines; the highest levels, 388 microg/L and 93 microg/L, respectively, were observed in the finished wine. Control wine (derived from fruit of unsmoked vines) contained 4 microg/L guaiacol, with the volatile phenols either not detected or detected at only trace levels (< or = 1 microg/L) throughout fermentation. The role of enzyme and acid catalyzed hydrolysis reactions in releasing smoke-derived volatile compounds was also investigated. The volatile phenols were released from smoked free run juice by strong acid hydrolysis (pH 1.0) and enzyme (beta-glucosidase) hydrolysis, but not mild acid hydrolysis (juice pH 3.2-3.7). Guaiacol was again the most abundant smoke-derived phenol, present at 431 microg/L and 325 microg/L in strong acid and enzyme hydrolysates, respectively. Only trace levels of each phenol could be detected in each control hydrolysate. This study demonstrates the potential for under-estimation of smoke taint in fruit and juice samples; the implications for the assessment of smoke taint and quantification of volatile phenols are discussed.

Although smoke exposure has been associated with the development of smoke taint in grapes and subsequently in wine, to date there have been no studies that have demonstrated a direct link. In this study, postharvest smoke exposure of grapes was utilized to demonstrate that smoke significantly influences the chemical composition and sensory characteristics of wine and causes an apparent 'smoke taint'. Verdelho grapes were exposed to straw-derived smoke for 1 h and then fermented according to two different winemaking treatments. Control wines were made by fermenting unsmoked grapes. Sensory studies established a perceivable difference between smoked and unsmoked wines; smoked wines were described as exhibiting 'smoky', 'dirty', 'earthy', 'burnt' and 'smoked meat' characteristics. Quantitative analysis, by means of gas chromatography-mass spectrometry, identified guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-ethylphenol, eugenol, and furfural in each of the wines made from smoked grapes. However, these compounds were not detected in the unsmoked wines, and their origin is therefore attributed to the application of smoke. Increased ethanol concentrations and browning were also observed in wines made from grapes exposed to smoke.

Background and Aims: Grapevine smoke exposure has been reported to produce smoke aromas in wine, resulting in 'smoke taint'. This study describes the application of smoke to field-grown grapevines between veraison and harvest to investigate the effect of timing and duration of smoke exposure on wine composition and sensory attributes. Methods and Results:Smoke was applied to grapevines as either a single smoke exposure to different vines at veraison or at 3, 7, 10, 15, 18 or 21 days post-veraison or repeated smoke exposures to the same vines at veraison and then at 3, 7, 10, 15, 18 and 21 days post-veraison. Gas chromatography-mass spectrometry analysis of guaiacol, 4-methylguaiacol, 4-ethylguaiacol and 4-ethylphenol showed elevated levels in all wines produced from fruit from smoked grapevines. Repeated smoke exposures had a cumulative effect on the concentration of these compounds. A trained sensory panel identified the aromas of 'burnt rubber', 'smoked meat', 'leather' and 'disinfectant' in all wines derived from smokeexposed grapevines but not in control wines. Conclusions: Smoke application to field-grown grapevines between veraison and harvest can influence the accumulation of volatile phenols and intensity of smoke aromas in resultant wines. A peak period of vine sensitivity to smoke at 7 days post-veraison is identified. Repeated smoke exposures have a cumulative effect. Significance of the Study: This is the first study to report the deliberate and controlled smoke application to field-grown grapevines demonstrating the timing and duration of smoke exposure to significantly affect wine chemical and sensory characters. AbbreviationsBET best estimate threshold; FAN free amino nitrogen; GC-MS gas chromatography-mass spectrometry; PCA principal component analysis; TSS total soluble solids.

Background and Aims: The chemical composition and sensory properties of smoke-affected grapes and wine has been the subject of several recent studies. However, while this research has addressed early knowledge gaps surrounding the effect of smoke on grapes and wine, to date, no practical solutions that mitigate the incidence or severity of smoke taint have been reported. The current project therefore aimed to identify winery processing methods that minimise the sensory impact of smoke taint in wine. Methods and Results: Different winemaking techniques were used to process smoke-affected grapes, i.e. cold maceration, the use of different yeast strains for primary fermentation and the use of oak and tannin additives. The extent of smoke taint in the resulting wines was determined by quantification of volatile phenols using GC-MS, followed by descriptive sensory analysis. Conclusions: Applied winemaking practices showed significant impacts on reducing the negative implications of smoke exposure on the chemical composition and sensory properties of wines. Winery processing methods that reduced skin contact time enhanced fruit character, produced wines with reduced 'smoke' aromas and flavours and less apparent taint. Selected yeast strains can be used as a tool for altering smoke-related aromas, flavours, colour and chemical composition of wines. The addition of oak chips and tannin enhanced the complexity of wines thereby reducing the perception of smoke-related attributes. Significance of the Study: These findings will enable winemakers to make more informed decisions when processing smoke-affected grapes, in order to minimise the severity of smoke taint perception in resulting wine.

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Wine made from grapes exposed to bushfire smoke can exhibit unpleasant smoky, ashy characters, which have been attributed to the presence of smoke-derived volatile phenols, in free or glycosylated forms. Here we report the uptake and glycosylation of volatile phenols by grapes following exposure of Cabernet Sauvignon vines to smoke, and their fate during winemaking. A significant delay was observed in the conversion of volatile phenols to their corresponding glycoconjugates, which suggests sequestration, the presence of intermediates within the glycosylation pathway and/or other volatile phenol storage forms. This finding has implications for industry in terms of detecting smoke-affected grapes following vineyard smoke exposure. The potential for an in-canopy sprinkler system to mitigate the uptake of smoke-derived volatile phenols by grapes, by spraying grapevines with water during smoke exposure, was also evaluated. While “misting” appeared to partially mitigate the uptake of volatile phenols by grapes during grapevine exposure to smoke, it did not readily influence the concentration of volatile phenols or the sensory perception of smoke taint in wine. Commercial sensors were used to monitor the concentration of smoke particulate matter (PM) during grapevine exposure to low and high density smoke. Similar PM profiles were observed, irrespective of smoke density, such that PM concentrations did not reflect the extent of smoke exposure by grapes or risk of taint in wine. The sensors could nevertheless be used to monitor the presence of smoke in vineyards during bushfires, and hence, the need for compositional analysis of grapes to quantify smoke taint marker compounds.

Insects have long been consumed as part of the diets of many Asian, African, and South American cultures. However, despite international agencies such as the Food and Agriculture Organization of the United Nations advocating the nutritional, environmental, and economic benefits of entomophagy, attitudinal barriers persist in Western societies. In Australia, the indigenous ‘bush tucker’ diet comprising witchetty grubs, honey ants, and Bogong moths is quite well known; however, in most Australian locales, the consumption of insects tends to occur only as a novelty. Therefore, this study aimed to investigate the awareness and acceptance of insects as food. An online survey of 820 consumers found that 68% of participants had heard of entomophagy, but only 21% had previously eaten insects; witchetty grubs, ants, grasshoppers, and crickets were the most commonly tasted insects. Taste, appearance, safety, and quality were identified as the factors that were most likely to influence consumer willingness to try eating insects, but consumer attitudes towards entomophagy were underpinned by both food neophobia (i.e., reluctance to eat new or novel foods) and prior consumption of insects. Neophobic consumers were far less accepting of entomophagy than neophilic consumers, while consumers who had previously eaten insects were most accepting of insects as food. Incorporating insects into familiar products (e.g., biscuits) or cooked meals also improved their appeal. Collectively, these findings can be used by the food industry to devise production and/or marketing strategies that overcome barriers to insect consumption in Australia.