Yeast strain affects 3-isopropyl-2-methoxypyrazine concentration and sensory profile in Cabernet Sauvignon wine

Abstract

Background and Aims: 3‐Isopropyl‐2‐methoxypyrazine (IPMP) is both a grape‐ and insect‐derived trace compound found in wine that can contribute green characters. There has been renewed interest in examining how wine IPMP concentrations can be modulated due to recent concerns regarding ladybug taint – an off‐flavour from IPMP extracted from Harmonia axyridis (Pallas) (multicoloured Asian lady beetle). This study sought to determine the influence of commercial Saccharomyces yeast strains on IPMP concentration in Cabernet Sauvignon wines and to describe their sensory impact. Methods and Results: Rehydrated juice from Cabernet Sauvignon concentrate was spiked with 30 ng/L IPMP and fermented in triplicate by yeast strains Lalvin BM45, Lalvin EC1118, Lalvin ICV‐D21 or Lalvin ICV‐D80. IPMP concentration was determined using headspace solid‐phase micro‐extraction coupled with gas chromatography mass spectrometry (HS‐SPME‐GC‐MS), and was unchanged from juice levels in wine fermented by EC1118, Lalvin D21 and Lalvin D80 but increased by 11 ng/L (29%) in wine fermented by Lalvin BM45. Yeast strains differed in their sensory impact on wine made from IPMP‐spiked juice for five aroma and four flavour attributes. Conclusions: HS‐SPME‐GC‐MS allows for sensitive measurement of IPMP that, for the first time, has demonstrated the capacity for wine yeast to affect IPMP concentration. Yeast strains demonstrate varying ability to mask green or ladybug taint characters in wine. Significance of the Study: This information should be useful in guiding selection of yeast strains for juices of high IPMP concentration, including those that are multicoloured Asian lady beetle‐affected, under‐ripe or from varieties with high methoxypyrazine loads such as Cabernet Sauvignon.

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

“…To prepare the sample, 0.90 mL of the diluted wine was added to a 20 mL amber round-bottomed glass vial containing a magnetic stir bar together with 3 g NaCl and 8.06 mL of acidified Milli-Q water. 40 µL of octanal-d 16 Standard C was added immediately and capped with a magnetic screw/thread headspace cap PTFE/silicone.…”

“…Standard A and Standard C composite standards were made up fresh on the day of analysis and the Milli-Q water and matrix were acidified to pH 3.6 with 1 M HCl. Vials were closed with Sun-sri magnetic screw/thread headspace cap PTFE/silicone closures and octanal-d 16 was used as the internal standard.…”

“…Similarly, thermo-vinification and juice heating can be moderately successful (up to 50% MP reduction) [14], but may lead to undesirable sensorial changes in wines [15]. Selective yeast usage was shown to be ineffective or even detrimental, with one commercial yeast strain increasing MP concentrations [16]. Bentonite fining does not remove MPs, and although fining with charcoal is moderately effective, it lacks the necessary selectivity [11].…”

Quantitative Survey of 3-alkyl-2-methoxypyrazines and First Confirmation of 3-ethyl-2-methoxypyrazine in South African Sauvignon blanc Wines

“…It has been reported that different yeast strains have an effect on the yield of wine MPs from the juice (Marais, 2004;Pickering et al, 2008). The correlation of VA with MP levels therefore possibly may be ascribed to the effect of different yeast strains on the production of acetic acid and MPs in the wine.…”

“…Marais et al (1999) reported that canopy microclimate plays a particularly important role in determining grape MP levels and that exposure to solar radiation, as manipulated by canopy management, has a more prominent effect than climatic temperature alone. Viticultural practices (Marais et al, 1999;Maggu et al, 2007) and the yeast strain used (Pickering et al, 2008) also affect wine MP concentrations. Moreover, possible infestations with lady beetles may also contribute MPs to affected wines.…”