Isobutylmethoxypyrazine Research Articles

Enhancing the sensory properties and consumer acceptance of warm climate red wine through blending

Proline has recently been found to direct several sensory attributes in red wine, including viscosity, fruit flavour and sweetness. We sought to investigate whether a red wine, deemed ‘flavour deficient’ by a producer, from a warm inland region could be improved by blending with a high proline wine from the same region, compared to a high colour and flavour wine, linking consumer acceptance with sensory properties and chemical composition. Three dry red wines (two Cabernet-Sauvignon wines from a warm region and one Lagrein wine from a cooler region) were blended in a constrained mixture design. Several blends were uncovered with improved sensory properties and consumer liking scores. Increased liking scores were related to heightened perceived Viscosity (unrelated to physical viscosity), Sweetness and Berry flavours, connected to proline-rich wines with small proportions of Lagrein. PLS-R models relating blend chemical composition, sensory properties and consumer acceptance associated Astringency and Bitterness to polyphenolics and organic acids and lower liking scores. Vegetal and Leather aromas in blends also reduced consumer acceptance and were related to the concentration of the thiols 3SH, 3SHA, PMT, 2FMT and MeSH, as well as guaiacol and isobutyl methoxypyrazine. Multiple blends successfully improved consumer acceptance of the ‘flavour deficient’ wine, particularly those with an increased proportion of the proline-rich wine. Non-linear effects resulting from blending were also assessed, with most variables modelled best by linear averaging. This study demonstrates the practical application of a design of experiment approach using sensory properties, proline and polyphenolic concentrations to guide wine blending and improve wine flavour and acceptability.

Chemical and Sensory Evaluation of Silicone and Polylactic Acid-Based Remedial Treatments for Elevated Methoxypyrazine Levels in Wine.

Alkylmethoxypyrazines (MPs) are a class of compounds that can elicit undesirable aroma and flavor characteristics in wine, and resist remediation using traditional wine making approaches. MPs are grape-derived constituents as well as contaminants from Coccinellidae beetles present during wine processing; the latter eliciting an off-flavor referred to as ‘ladybug taint’. In this study we investigated the capacity of two plastic polymers—one silicone-based, the other polylactic acid-based—applied with varying surface areas to reduce concentrations of isopropylmethoxypyrazine (IPMP), sec-butylmethoxypyrazine (SBMP) and isobutylmethoxypyrazine (IBMP) in a Merlot wine using multi-dimensional gas chromatography coupled with mass spectrometry and headspace solid phase microextraction (SPME-MDGCMS). The impact of treatments on the sensory characteristics of the wine (descriptive analysis) and volatile aroma compounds (VOCs) (SPME-MDGCMS) was also investigated. Results showed substantial reductions for all of the target odorants: up to 38%, 44% and 39% for IPMP, SBMP and IBMP, respectively, for the silicone polymer, and up to 75%, 78% and 77% for IPMP, SBMP and IBMP, respectively, for the polylactic acid polymer. These polymers had no or minimal effect on VOCs at applications of 200 cm2/L for silicone or for all polylactic acid treatments. Sensory impacts were less clear, but generally showed minimal effect from the treatments. Taken overall, the data confirm the utility of both polylactic acid and silicone polymers in reducing elevated levels of grape-derived MPs, as well as potentially improving wine contaminated by ladybug taint.

Application of plastic polymers in remediating wine with elevated alkyl-methoxypyrazine levels

3-Alkyl-2-methoxypyrazines (MPs) are odour-active compounds that elicit atypical green aromas and flavours in some wines, and are resilient to removal using traditional wine-making approaches. They originate either as contaminants from Coccinellidae beetles inadvertently introduced during wine processing (“ladybug taint”) or as grape-derived constituents that are undesirable at elevated levels. In this study we investigated the capacity of a selection of plastic polymers to reduce concentrations of three MPs: isopropyl methoxypyrazine (IPMP), secbutyl methoxypyrazine (SBMP) and isobutyl methoxypyrazine (IBMP). In Trial 1, red wine was spiked with IPMP (20 ng/l), SBMP (20 ng/l) and IBMP (20 ng/l), then separately treated with 13 plastic polymers (surface area 350 cm2/l). Three polymers were then identified for further testing based on the results from Trial 1: silicone, ethylene and vinyl acetate (EVA) and a poly-lactic acid-based biodegradable polymer. In Trial 2, the efficacy of these selected polymers to reduce MP levels in red wine was tested as a function of contact time. Solid-phase micro-extraction multi-dimensional GC-MS was used to measure MP levels before and after treatment with the polymers. Results showed significant reductions in all target odorants after 24 h treatment: silicone reduced IPMP and IBMP by 96% and 100%, respectively, while the biodegradable polymer decreased IPMP and IBMP concentrations by 52% and 36%, respectively. EVA was less effective in lowering MP levels (7% IPMP and 23% IBMP after 24 h). Taken overall, the data suggest the potential for the use of poly-lactic acid and silicone in treating wines contaminated by ladybug taint, as well as in reducing high levels of grape-derived MPs.

Novel Applications for Biomaterials: The Case of Remediation of Wine Taints Using Poly-Lactic Acid Polymer

Wine is the world’s oldest alcoholic beverage and the most consumed in at least 20 countries. However, taints detract from its quality and acceptance, significantly reducing the value of wine. In this study we investigated the capacity of a poly-lactic acid (PLA) biopolymer to reduce concentrations of four odorants responsible for tainting many red wines:isopropyl-methoxypyrazine (IPMP),isobutyl–methoxypyrazine (IBMP), 4-ethylphenol (4-EP) and 4-ethylguaiacol (4-EG). Red wine was spiked with either IPMP [20 ng/L] and IBMP [20 ng/L] (Study 1) or 4-EP [200 ug/L] and 4-EG [200 ug/L] (Study 2) and then treated with a PLA film [surface area 350 cm2/L]. Solid Phase Micro-Extraction Multi-Dimensional Gas Chromatography–Mass Spectrometry and Gas Chromatography-Mass Spectrometry were used to measure the methoxypyrazines and ethylphenols, respectively, both before and after treatment with PLA. Results showed significant reductions in all of the target odorants after 8hrs treatment: IPMP (51%), IBMP (26%), 4-EP (21%) and 4-EG (20%). Taken overall, the data suggest potential for the use of PLA in treating common wine faults, particularly ‘ladybug taint’, which is caused by elevated levels of IPMP.

Development of a rapid method for the quantitative analysis of four methoxypyrazines in white and red wine using multi-dimensional Gas Chromatography – Mass Spectrometry

Alkyl-methoxypyrazines (MPs) are important odour-active constituents of many grape cultivars and their wines. Recently, a new MP – 2,5-dimethyl-3-methoxypyrazine (DMMP) – has been reported as a possible constituent of wine. This study sought to develop a rapid and reliable method for quantifying DMMP, isopropyl methoxypyrazine (IPMP), secbutyl methoxypyrazine (SBMP) and isobutyl methoxypyrazine (IBMP) in wine. The proposed method is able to rapidly and accurately resolve all 4 MPs in a range of wine styles, with limits of detection between 1 and 2ngL−1 for IPMP, SBMP and IBMP and 5ngL−1 for DMMP. Analysis of a set of 11 commercial wines agrees with previously published values for IPMP, SBMP and IBMP, and shows for the first time that DMMP may be an important and somewhat common odorant in red wines. To our knowledge, this is the first analytical method developed for the quantification of DMMP in wine.

Relationships between harvest time and wine composition in Vitis vinifera L. cv. Cabernet Sauvignon 1. Grape and wine chemistry

The study aimed to quantify the effects of grape maturity on wine alcohol, phenolics, flavour compounds and polysaccharides in Vitis vinifera L. cv Cabernet Sauvignon. Grapes were harvested at juice soluble solids from 20 to 26 °Brix which corresponded to a range of wine ethanol concentrations between 12% and 15.5%. Grape anthocyanin and skin tannin concentration increased as ripening progressed, while seed tannin declined. In the corresponding wines, monomeric anthocyanin and wine tannin concentration increased with harvest date, consistent with an enhanced extraction of skin-derived phenolics. In wines, there was an observed increase in yeast-derived metabolites, including volatile esters, dimethyl sulfide, glycerol and mannoproteins with harvest date. Wine volatiles which were significantly influenced by harvest date were isobutyl methoxypyrazine, C6 alcohols and hexyl acetate, all of which decreased as ripening progressed. The implications of harvest date for wine composition is discussed in terms of both grape composition and yeast metabolism.

Occurrence and contribution of alkyl methoxypyrazines in wine tainted by Harmonia axyridis and Coccinella septempunctata

Ladybug taint (LBT) is a wine fault caused by the inadvertent incorporation of ladybeetles to the wine during the winemaking process. Harmonia axyridis, also known as the multicolored Asian lady-beetle (MALB), was the only species considered responsible for causing the taint. A second species, Coccinella septempunctata (7 Spot), has recently also been implicated. The main objectives of this study were to identify and quantify the compounds associated with ladybug taint of white and red wine from these two Coccinellidae species (Harmonia axyridis and Coccinella septempunctata), and determine the most odor-active compounds in LBT-affected wines. Results show that Coccinellidae can contribute dimethyl, isopropyl, secbutyl and isobutyl methoxypyrazine to wine when they are processed with grapes, and that the methoxypyrazine composition varies between MALB and 7 Spot. Isopropyl methoxypyrazine is the major contributor to LBT in wines produced with these ladybeetle species, although secbutyl and isobutyl methoxypyrazine may contribute in MALB- and 7 Spot-affected wines, respectively. Finally, dimethyl methoxypyrazine is reported for the first time in wines not affected by Coccinellidae; the global significance and prevalence of this compound in wine remains to be determined. Both Harmonia axyridis and Coccinella septempunctata can contribute alkyl methoxypyrazines, and particularly isopropyl methoxypyrazine, to wine at concentrations that can have a negative impact on wine quality. These findings will allow grape growers and winemakers to be more aware of the risks posed by 7 Spot beetles, and to take the appropriate preventative and remedial actions. Furthermore, this is the first time dimethyl methoxypyrazine is reported in wine, either as an endogenous or Coccinellidae-derived odorant.

Sensory and chemical characterisation of Sauvignon blanc wine: Influence of source of origin

The main objective of the study was to investigate influence of geographical location on volatile composition and perceived flavour profile of Sauvignon wines of New Zealand (Marlborough), French (Sancerre; Loire; Saint Bris), and Austrian (Styria) origin. Nineteen New Zealand wine professionals evaluated 18 Sauvignon wines, 6 from each source of origin, by sensory methods that included intensity ratings to experimenter-provided descriptors, typicality ratings, and classification tasks (non-directed and directed sorting). Results demonstrated that wines from the three sources of origin were separated by sensory analyses, with New Zealand wines dominated by perceived green characteristics, Austrian wines perceived to be fruity (stone-fruit), and French wines relatively subdued in all characteristics measured other than perceived minerality. Concentrations of fermentation-derived, volatile aroma compounds (including acetate esters, fatty acid ethyl esters, and higher alcohols) and isobutylmethoxypyrazine (IBMP) were determined for each wine using the automated HS-SPME (Headspace Solid-Phase Micro-Extraction) technique (Parr et al., 2007) and a modification of the HS-SPME technique (Kemp, 2010). Analysis of thiol concentrations was undertaken by SPME-GC–MS/MS analysis. Statistical association of sensory and chemical data demonstrated that the chemical compounds clustered into three groups, each cluster associated with one source-of-origin. A ‘green’ cluster of compounds associated with the New Zealand wines, the fruity/boxwood compound 4-mercapto-4-methylpentan-2-one (4MMP) associated with Austrian wines, and other compounds (e.g., benzaldehyde) associated with French wines. The study has demonstrated differences in perceived sensory characteristics and chemical composition of Sauvignon wines as a function of source of origin, and demonstrated associations between some specific aroma compounds and sensory terms employed by wine professionals. Highlights ► We investigate influence of three geographical origins on Sauvignon blanc wine. ► Sensory characteristics and chemical composition of wines are examined. ► Perceived flavor differences were found as a function of wine origin. ► Chemical composition of Sauvignon wines also differed as a function of wine origin.

Effect of polyphenols on the perception of key aroma compounds from Sauvignon Blanc wine

Background and Aims: Sensory wine research has mainly focused on the role of volatile compounds and their contribution to the aroma profile. Wines also contain polyphenolic compounds, which are not volatile. This research begins to investigate the interactions of volatile and non-volatile wine compounds and the consequential effects on sensory perception of aroma. Methods and Results: Trained panellists of this study measured the perception of four aroma compounds (isobutyl methoxypyrazine, 3-mercaptohexanol, 3-mercaptohexanol acetate and ethyl decanoate) in wine. Panellists assessed the four compounds in combinations with three polyphenols (catechin, caffeic acid and quercetin) commonly found in white wine. The perception of isobutyl methoxypyrazine, 3-mercaptohexanol and ethyl decanoate was largely suppressed by the added polyphenols, while the perception of 3-mercaptohexanol was accentuated with the addition of caffeic acid. Of the three polyphenols, only catechin had a slight effect of accentuating the mercaptohexanol acetate perception. Conclusions: Results showed each polyphenol had a unique effect when blended with a specific aroma compound, either suppressing, accentuating or showing little effect on the perception of the aroma compounds. Significance of the Study: Understanding these interactions can assist winemakers in managing polyphenol levels to optimize selected volatile compounds to achieve desirable aroma profiles.

Odorant response of isolated olfactory receptor cells is blocked by amiloride.

Olfactory receptor cells were isolated from the nasal mucosa of Rana esculenta and patch clamped. Best results were obtained with free-floating cells showing ciliary movement. 1) On-cell mode: Current records were obtained for up to 50 min. Under control conditions they showed only occasional action potentials. The odorants cineole, amyl acetate and isobutyl methoxypyrazine were applied in saline by prolonged superfusion. At 500 nanomolar they elicited periodic bursts of current transients arising from cellular action potentials. The response was rapidly, fully and reversibly blocked by 50 microM amiloride added to the odorant solution. With 10 microM amiloride, the response to odorants was only partially abolished. 2) Whole-cell mode: Following breakage of the patch, the odorant response was lost within 5 to 15 min. Prior to this, odorants evoked a series of slow transient depolarizations (0.1/sec, 45 mV peak to peak) which reached threshold and thus elicited the periodic discharge of action potentials. These slow depolarizing waves were reversibly blocked by amiloride, which stabilized the membrane voltage between -80 and -90 mV. We conclude that amiloride inhibits chemosensory transduction of olfactory receptor cells, probably by blocking inward current pathways which open in response to odorants.