Gary J. Pickering

Astringency: Mechanisms and Perception

Astringency plays an important role in the sensory experience of many foods and beverages, ranging from wine to nuts. Given the recent trend toward fortifying consumables with astringent compounds and the evidence regarding the health benefits of some astringents, the mechanisms and perceptual characteristics of astringency warrant further discussion and investigation. This paper reviews the current state of the literature, including consideration of new methods for describing and measuring astringency, and provides an overview of research concerned with elucidating the physical, physiological, and psychological factors that underlie and mediate perception of this sensation.

Low- and reduced - alcohol wine: a review

This paper reviews the technologies available for the production of dealcoholised, low- and reduced-alcohol wines. While the sensory quality in the early years was in many instances unsatisfactory, significant improvements in production methods have occurred, with technologies based on membranes and spinning cones now the most commonly used. Lower processing temperatures, improved aroma retention and recovery and a better understanding of the role of adjuncts in addressing flavour imbalances have led to a general improvement in overall quality. The continuing consumer resistance towards these wines in many market sectors is also discussed. It is concluded that this may be largely attributable to ongoing limitations in sensory quality and to promotional issues, including limited advertising budgets and a low level of awareness of recent improvements in quality.

Intensity of taste and astringency sensations elicited by red wines is associated with sensitivity to PROP (6-n-propylthiouracil)

Abstract The relationship between sensitivity to 6-n-propylthiouracil (PROP) and taste and astringency perception elicited by red wines was examined. Twenty-five subjects were classified into three PROP sensitivity groups (non-tasters, tasters and super-tasters) based on their bitterness ratings of a 0.32 mM PROP solution as measured on a Labeled Magnitude Scale (LMS). In a completely randomized block design, subjects used the LMS to rate the bitterness, astringency and acidity intensities of three commercial red wines. Contrary to the findings of previous studies with wine, bitterness, astringency and acidity intensities were all correlated with individual PROP taster status. PROP non-tasters gave significantly lower intensity ratings for the bitterness, astringency and acidity of the red wines than did PROP tasters and super-tasters. Individual differences among taster groups may be related to preference and consumption behavior of consumers of wine and other alcoholic beverages.

Behavioural Segmentation: A New Zealand Wine Market Application

As a subject, market segmentation has a long, debated history in marketing literature. Its application to the wine industry seems to be in its infancy and needing careful assessment. This paper examines various approaches to market segmentation as applied in the wine industry. Also discussed is information on, and an assessment of, a behavioural segmentation study conducted on a sample of New Zealanders. The basis for this information is a mail survey of 1144 randomly selected potential respondents. Respondents were drawn from a national wine mailing list (n=640) and staff (n=304) and students (n=200) from a tertiary institute. No follow-up activity was undertaken and a 28% response rate was achieved. A range of behavioural and demographic information was collected. In particular, participants were asked to indicate on average how many bottles of wine they purchased per month. This information forms the basis of segmenting on volumes purchased and, together with other behavioural information, combines to form profiles of wine consumers. Significant differences were found between light, medium and heavy purchasers of wine for several characteristics. While the segmentation platform provides some useful information, its use highlights the absence of other pertinent information. It is concluded that underlying reasons or motivations contributing to group membership would enrich the behavioural segmentation platform.

Quantitative analysis of 3-alkyl-2-methoxypyrazines in juice and wine using stable isotope labelled internal standard assay

A solid phase microextraction (HS-SPME)-GC-MS methodology was established for the analysis of 3-alkyl-2-methoxypyrazines (MPs) in wine using a stable isotope dilution assay. The compounds analysed were 3-isobutyl-2-methoxypyrazine (IBMP), 3-sec-butyl-2-methoxypyrazine (SBMP), and 3-isopropyl-2-methoxypyrazine (IPMP) using their respective deuterated analogues ([2H3]-IBMP, [2H3]-SBMP, [2H3]-IPMP) as internal standards, synthesised during this work. A divinylbenzene/carboxene/polydimethylsiloxane (DVB/CAR/PDMS) fibre was selected for isolation of MPs and the effects of matrix parameters such as pH and ethanol concentration were examined in the development of the method. Best results were obtained at a pH of approximately 6 and with a wine dilution factor of 1:2.5, resulting in an ethanol concentration of approximately 5% (v/v). Relative standard deviations (RSDs) of replicate samples were 5.6-7% for all MPs at 5 ng L(-1) and <5% for 15 and 30 ng L(-1) samples. The limit of detection was <0.5 ng L(-1) in juice and 1-2 ng L(-1) in wine. The recovery efficiencies for spiked wine samples were between 99 and 102% for all three MPs. Using this method, we investigated the impact of the Multicoloured Asian Lady Beetle (MALB) on MPs in wine. In red wine fermented with live MALB, IPMP is the most prevalent MP detected, although SBMP concentrations are also increased and IBMP is unchanged from background levels. MALB that have been dead for 1 day before addition to juice can still contribute to elevated SBMP concentrations in wine, but not if they have been dead for 3 days or longer. Clarifying juice prior to fermentation leads to substantially lower IPMP concentration in the subsequent wine when compared with unclarified juice.

Effect of closure and packaging type on 3-alkyl-2-methoxypyrazines and other impact odorants of Riesling and Cabernet Franc wines.

3-Alkyl-2-methoxypyrazines (MPs) represent an important and potent class of grape- and insect-derived odor-active compounds associated with wine quality. Thirty nanograms per liter each of 3-isobutyl-2-methoxypyrazine (IBMP), 3-isopropyl-2-methoxypyrazine (IPMP), and 3-sec-butyl-2-methoxypyrazine (SBMP) was added to Riesling and Cabernet Franc wines and monitored with headspace solid-phase microextraction and gas chromatography-mass spectrometry over 18 months to investigate the effects of various closure and packaging options on MPs. Changes in MP concentrations during bottle aging varied with closure/packaging option, with the greatest decrease evident in Tetrapak cartons. After 18 months, IBMP, IPMP, and SBMP in both Tetrapak-stored wines decreased by approximately 45, 32, and 26%, respectively. Similar changes were observed in other impact odorants to previous studies, including a greater decrease in odorant concentrations in wines closed with synthetic corks compared to natural corks and screw caps. These differences are thought to be due to the differential sorptive capacities of the various closure types. Overall, the data suggest that differences in gas permeability/contribution from the different closure and packaging options strongly associate with changes in wine composition during aging.

Wine Expertise Predicts Taste Phenotype.

Taste phenotypes have been studied in relation to alcohol intake, dependence, and family history, with contradictory findings. However, on balance—with appropriate caveats about populations tested, outcomes measured, and psychophysical methods used—an association between variation in taste responsiveness and some alcohol behaviors is supported. Recent work suggests supertasting (operationalized via propylthiouracil [PROP] bitterness) associates not only with heightened response but also with more acute discrimination between stimuli. This work examined relationships between food and beverage adventurousness and taste phenotype. A convenience sample of wine drinkers (n = 331) was recruited in Ontario and phenotyped for PROP bitterness via filter paper disk. The subjects also completed a short questionnaire regarding willingness to try new foods, alcoholic beverages, and wines as well as level of wine involvement, which was used to classify each one as a wine expert (n = 111) or a wine consumer (n = 220). In univariate logisitic models, food adventurousness predicted trying new wines and beverages but not expertise. Likewise, wine expertise predicted willingness to try new wines and beverages but not foods. In separate multivariate logistic models, willingness to try new wines and beverages was predicted by expertise and food adventurousness but not PROP. However, mean PROP bitterness was higher among wine experts than wine consumers, and the conditional distribution functions differed between experts and consumers. In contrast, PROP means and distributions did not differ with food adventurousness. These data suggest individuals may self-select for specific professions based on sensory ability (i.e., an active gene-environment correlation), but phenotype does not explain willingness to try new stimuli.

Modifying Bitterness in Functional Food Systems

The functional foods sector represents a significant and growing portion of the food industry, yet formulation of these products often involves the use of ingredients that elicit less than desirable oral sensations, including bitterness. Promising new functional ingredients, including polyphenolics, may be more widely and readily employed in the creation of novel functional foods if their aversive bitter taste can be significantly reduced. A number of approaches are used by the industry to improve the taste properties and thus the acceptance of conventional foods that elicit excessive bitterness. This article reviews the most commonly employed techniques, including the use of bitter-modifying additives, which may prove useful for successfully introducing new functional ingredients into this rapidly growing sector.

Determination of odour detection thresholds for acetic acid and ethyl acetate in ice wine

Abstract Collectively acetic acid and ethyl acetate are responsible for ‘volatile acidity’ (VA) in wine. The detection limit or threshold for these compounds is well documented in table wine but not for ice wine. Knowledge of the ice wine thresholds is important for understanding perception limits and setting legal standards, particularly for a product with high intrinsic concentrations. Thresholds were determined for each compound using seventeen subjects and an ascending series of paired comparison tests, consisting of five concentrations. The detection threshold, the concentration at which there is 75% correct detection, was determined using least-squares linear regression. The correlation coefficients for the linear regressions for acetic acid and ethyl acetate were r = 0.996 (p < 0.001) and r = 0.972 (p < 0.001), respectively. The thresholds for acetic acid and ethyl acetate were 3.185 and 0.198 g/l, respectively. The threshold for acetic acid was approximately three times that found in table wines, but was relatively unchanged for ethyl acetate. This work supports the need for the legal limit for VA to be higher in ice wine, but also suggests that the legal requirements for the two compounds should be specified independently, not together.

Inhibition of human lung cancer cell proliferation and survival by wine

BackgroundCompounds of plant origin and food components have attracted scientific attention for use as agents for cancer prevention and treatment. Wine contains polyphenols that were shown to have anti-cancer and other health benefits. The survival pathways of Akt and extracellular signal-regulated kinase (Erk), and the tumor suppressor p53 are key modulators of cancer cell growth and survival. In this study, we examined the effects of wine on proliferation and survival of human Non-small cell lung cancer (NSCLC) cells and its effects on signaling events.MethodsHuman NSCLC adenocarcinoma A549 and H1299 cells were used. Cell proliferation was assessed by thymidine incorporation. Clonogenic assays were used to assess cell survival. Immunoblotting was used to examine total and phosphorylated levels of Akt, Erk and p53.ResultsIn A549 cells red wine inhibited cell proliferation and reduced clonogenic survival at doses as low as 0.02%. Red wine significantly reduced basal and EGF-stimulated Akt and Erk phosphorylation while it increased the levels of total and phosphorylated p53 (Ser15). Control experiments indicated that the anti-proliferative effects of wine were not mediated by the associated contents of ethanol or the polyphenol resveratrol and were independent of glucose transport into cancer cells. White wine also inhibited clonogenic survival, albeit at a higher doses (0.5-2%), and reduced Akt phosphorylation. The effects of both red and white wine on Akt phosphorylation were also verified in H1299 cells.ConclusionsRed wine inhibits proliferation of lung cancer cells and blocks clonogenic survival at low concentrations. This is associated with inhibition of basal and EGF-stimulated Akt and Erk signals and enhancement of total and phosphorylated levels of p53. White wine mediates similar effects albeit at higher concentrations. Our data suggest that wine may have considerable anti-tumour and chemoprevention properties in lung cancer and deserves further systematic investigation in animal models of lung cancer.