Determination of Ortho‐ and Retronasal Detection Thresholds for 2‐Isopropyl‐3‐Methoxypyrazine in Wine

Abstract

2-Isopropyl-3-methoxypyrazine (IPMP) is a grape-derived component of wine flavor in some wine varieties as well as the causal compound of the off-flavor known as ladybug taint (LBT), which occurs when Harmonia axyridis beetles are incorporated with the grapes during juice and wine processing. The main objective of this study was to obtain robust estimates of the orthonasal (ON) and retronasal (RN) detection thresholds (DTs) for IPMP in wines of differing styles. The ASTM E679 ascending forced choice method of limits was used to determine DTs for 47 individuals in 3 different wines--Chardonnay, Gewürztraminer, and a red wine blend of Baco Noir and Marechel Foch. The group best estimate thresholds (BETs) obtained for IPMP (ng/L) were Chardonnay, ON: 0.32; Gewürztraminer, ON: 1.56, RN: 1.15, and red wine blend, ON: 1.03, RN: 2.29. A large variation in individual DTs was observed. Familiarity with LBT was inversely correlated with DTs for Gewürztraminer, and no difference in thresholds was observed between winemakers and nonwinemakers. We conclude that the human DT for IPMP is extremely low and influenced significantly by wine style and evaluation mode. We recommend against the reporting of single-threshold values for wine flavor compounds, and encourage the determination of consumer rejection thresholds for IPMP in wine.

The Training Level of Experts Influences their Detection Thresholds for Key Wine Compounds

“…Pickering et al (2007) exploring sensitivity of 2-isopropyl-3-methoxypyrazine in wine showed that winemakers have lower detection threshold than non-winemakers. They explained this result by a familiarization with the related wine defect was thus invoked rather than a gain in olfactory acuity.…”

Effect of light and temperature on 3-alkyl-2-methoxypyrazine concentration and other impact odourants of Riesling and Cabernet Franc wine during bottle ageing

“…3-Alkyl-2-methoxypyrazines (MPs) are powerful, odourous components of many wines, where thresholds have been reported as low as 320 pg/L (Pickering, Karthik, Inglis, Sears, & Ker, 2007). 3-Isopropyl-2-methoxypyrazine (IPMP), 3-s-butyl-2-methoxypyrazine (SBMP) and 3-isobutyl-2-methoxypyrazine (IBMP) are secondary plant metabolites that are most abundant in grape Vitis vinifera varieties that originate from the Bordeaux region in France, especially Cabernet Sauvignon (Allen, Lacey, & Boyd, 1994;Kotseridis, Baumes, Bertrand, & Skouromounis, 1999).…”

Determining odour detection thresholds: Incorporating a method-independent definition into the implementation of ASTM E679

“…The first judgement procedure is commonly used in experiments that involve simultaneous testing on multiple judges (Kolpin & Shellhammer, 2009;Pickering, Karthik, Inglis, Sears, & Ker, 2007;Plotto, Margaria, Goodner, Goodrich, & Baldwin, 2004;Stocking, Suffet, McGuire, & Kavanaugh, 2001). A full evaluation of all 3AFC trials is collected from each judge, and the threshold is estimated from the location in the series at which the response reversed from incorrect to correct for the last time.…”