Abstract
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.
Highlights
IntroductionWine aroma and flavor are influenced by hundreds of volatile compounds from many chemical classes (e.g., esters, aldehydes, alcohols, fatty acids, terpenes) but flavor and aroma balance are impacted when some compounds accumulate at higher than optimal concentrations for a particular wine variety or style. 3-Alkyl-2-methoxypyrazines (MPs) are powerful odorants, commonly found in the natural world
Wine aroma and flavor are influenced by hundreds of volatile compounds from many chemical classes but flavor and aroma balance are impacted when some compounds accumulate at higher than optimal concentrations for a particular wine variety or style. 3-Alkyl-2-methoxypyrazines (MPs) are powerful odorants, commonly found in the natural world
The main aims of this study were to evaluate the ability of silicone and polylactic acid polymers to reduce the concentrations of MPs in red wine, determine how this varies with polymer surface area, and elucidate the effects on other volatile aroma compounds and sensory quality
Summary
Wine aroma and flavor are influenced by hundreds of volatile compounds from many chemical classes (e.g., esters, aldehydes, alcohols, fatty acids, terpenes) but flavor and aroma balance are impacted when some compounds accumulate at higher than optimal concentrations for a particular wine variety or style. 3-Alkyl-2-methoxypyrazines (MPs) are powerful odorants, commonly found in the natural world. Wine aroma and flavor are influenced by hundreds of volatile compounds from many chemical classes (e.g., esters, aldehydes, alcohols, fatty acids, terpenes) but flavor and aroma balance are impacted when some compounds accumulate at higher than optimal concentrations for a particular wine variety or style. MPs are found in many wine grape varieties such as Cabernet sauvignon, Cabernet franc, Carmeneré, Sauvignon blanc and Chardonnay [1,2], and they can contribute to wine typicity and complexity. Extraction of MPs from these beetles during winemaking procedures can lead to off-flavors known collectively as ladybug taint [3]. The taint in juice and wine is characterized by detrimental aromas and flavors that include “peanuts”, “asparagus”, “green bell pepper”, and “canned green beans” [3]. MPs are very potent, with olfactory perception thresholds ranging between 0.3–16 ng/L, and concentration ranges of 0–60 ng/L reported in commercial wines
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