Prevalence and Management of Alkyl-Methoxypyrazines in a Changing Climate: Viticultural and Oenological Considerations.

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.

Thermal Taster Subgroups and Orosensory Responsiveness Dataset.

Thermal taste is a phenomenon whereby some individuals, known as thermal tasters (TT) experience taste sensations when their tongue is warmed or cooled. It was first reported in 2000 by Cruz and Green [1] and since then, most research has focused on comparing TT to thermal non-tasters (TnT; individuals who do not experience thermally-elicited sensations). As TT rate the intensity of taste stimuli higher than TnT, understanding the nature of this difference may help inform how individual differences in taste perception impact consumer liking and consumption of food and beverages. However, as the mechanism(s) underlying thermal tasting are yet to be fully elucidated, it is unclear if TT should be considered a homogeneous group or if subgroups exist. We created a dataset to help determine if the orosensory advantage is universal across all TT, or if it is mainly attributable to one or more subgroups of TT. To this end, the thermal taste screening data of 297 TT from 12 previous recruitment drives ('cohorts') was combined. This created the largest dataset of TT reported to date in a single study, allowing for an in-depth analysis of the differences between TT. After training on appropriate scale use, participants were familiarized with common taste and chemesthetic stimuli (sweet, sour, salty, bitter, umami, astringent and metallic). Using a sip-and-spit protocol, participants rinsed with the stimuli and rated the maximum intensity each stimulus elicited on a generalized Visual Analogue Scale (gVAS) or a generalized Labeled Magnitude Scale (gLMS). To account for minor methodological differences between the cohorts, ratings from each cohort were first converted to z-scores before being combined into the overall dataset. Next, participants underwent a series of 12 trials that assessed response to a thermal elicitation device during which each combination of two temperature regimes (warming and cooling) and three lingual sites (tongue tip, 1 cm to left, 1 cm to the right) were examined in duplicate. Participants were asked to rate the maximum intensity of any sensations experienced during each trial. TT were classified into subgroups based on the type of thermally-elicited taste reported (typically sweet, sour, salty, bitter, metallic), the temperature regime during which the sensation was elicited (warming or cooling) and the location on the tongue tested at which the sensation was experienced. Figures are provided that show the mean intensity ratings of aqueous solutions of chemical stimuli and corresponding standard errors for each of the TT subgroups. In addition, the TT Subgroup Naming Conventions provided should allow for a consistent and clear use of terminology across future thermal taste research. Readers are referred to Homogeneity of thermal tasters and implications for mechanisms and classification[2] for a full discussion of how these findings inform our understanding of the mechanism(s) underlying thermal taste and the practical implications of methodological differences in determining thermal taste status.

Homogeneity of thermal tasters and implications for mechanisms and classification.

Thermal tasting, an important type of individual variation in orosensation, is a phenomenon by which some individuals perceive thermally-induced taste sensations simply by having the tip of their tongue warmed or cooled. These individuals, known as thermal tasters, report a variety of thermally-elicited tastes (typically sweet, sour, salty, bitter, metallic) and the tastes reported can vary with the temperature regime used (warming or cooling) and location on the tongue tested. Importantly, when compared to thermal non-tasters, thermal tasters are more responsive to aqueous solutions of basic tastants and to beverages. The mechanism(s) underlying thermal tasting are not well understood and it is unknown if the increased orosensory responsiveness of thermal tasters is universal or if it is driven by a subgroup of thermal tasters. Thermal taste data from 12 previous studies was combined to obtain a large sample of thermal tasters (n = 254) who were divided into subgroups based on the type of thermally-elicited taste reported and the temperature regime/location at which it was experienced. Sweet thermal tasters (n = 77) were 9 times more likely than non-sweet thermal tasters (n = 177) to experience thermally-elicited sensations during lingual warming (p < 0.0001). Similarly, sour thermal tasters (n = 89) were 8 times more likely than non-sour thermal tasters (n = 165) to report thermally induced tastes during cooling (p<0.0001). However, no differences in orosensory responsiveness based on these or other subgroups were identified, suggesting that the heightened orosensory responsiveness of thermal tasters may be centrally-mediated. We discuss how these findings inform our understanding of the mechanism(s) underlying thermal taste and the identification of thermal taste subgroups, along with practical implications of methodological differences in determining thermal taste status.

The role of taste in alcohol preference, consumption and risk behavior.

Alcohol consumption is widespread, and high levels of use are associated with increased risk of developing an alcohol use disorder. Thus, understanding the factors that influence alcohol intake is important for disease prevention and management. Additionally, elucidating the factors that associate with alcohol preference and intake in non-clinical populations allows for product development and optimisation opportunities for the alcoholic beverage industry. The literature on how taste (orosensation) influences alcohol behavior is critically appraised in this review. Ethanol, the compound common to all alcoholic beverages, is generally aversive as it primarily elicits bitterness and irritation when ingested. Individuals who experience orosensations (both taste and chemesthetic) more intensely tend to report lower liking and consumption of alcoholic beverages. Additionally, a preference for sweetness is likely associated with a paternal history of alcohol use disorders. However, conflicting findings in the literature are common and may be partially attributable to differences in the methods used to access orosensory responsiveness and taste phenotypes. We conclude that while taste is a key driver in alcohol preference, intake and use disorder, no single taste-related factor can adequately predict alcohol behaviour. Areas for further research and suggestions for improved methodological and analytical approaches are highlighted.

Orosensory responsiveness and alcohol behaviour.

Consumption of alcoholic beverages is widespread through much of the world, and significantly impacts human health and well-being. We sought to determine the contribution of orosensation ('taste') to several alcohol intake measures by examining general responsiveness to taste and somatosensory stimuli in a convenience sample of 435 adults recruited from six cohorts. Each cohort was divided into quantiles based on their responsiveness to sweet, sour, bitter, salty, umami, metallic, and astringent stimuli, and the resulting quantiles pooled for analysis (Kruskal-Wallis ANOVA). Responsiveness to bitter and astringent stimuli was associated in a non-linear fashion with intake of all alcoholic beverage types, with the highest consumption observed in middle quantiles. Sourness responsiveness tended to be inversely associated with all measures of alcohol consumption. Regardless of sensation, the most responsive quantiles tended to drink less, although sweetness showed little relationship between responsiveness and intake. For wine, increased umami and metallic responsiveness tended to predict lower total consumption and frequency. A limited examination of individuals who abstain from all alcohol indicated a tendency toward higher responsiveness than alcohol consumers to sweetness, sourness, bitterness, and saltiness (biserial correlation), suggesting that broadly-tuned orosensory responsiveness may be protective against alcohol use and possibly misuse. Overall, these findings confirm the importance of orosensory responsiveness in mediating consumption of alcohol, and indicate areas for further research.