Sensory Impact of 2-Methoxy-3-Isobutylpyrazine and 4-Mercapto-4- Methylpentan-2-0ne Added to a Neutral Sauvignon blanc Wine

Abstract

3-isohutylpyrazine, 4-mercapto-4-methylpentan-2-one, Sauvignon blanc aroma 2-Methoxy-3-isohutylpyrazine (ibMP) and 4-mercapto-4-methylpentan-2-one (MMP) are considered amongst the most important Sauvignon blanc impact aroma components. These two components were added, separately and in combination at increasing concentrations, to different media, i.e. deionised water, a neutral non-Sauvignon blanc white wine and a neutral Sauvignon blanc wine. The media were then sensorially evaluated. The nuances perceived, varied from dusty, grassy to green pepper for ihMP and from guava, sulphur-like to cat urine or "conifer" for MMP. It was confirmed that ibMP and MMP are important impact components and that their contribution, either positive or negative, varied according to medium type and composition, as well as to the concentration levels of the components. This may be ascribed to the combined synergistic action of these two components. Other typical Sauvignon blanc aroma nuances, such as asparagus, gooseberry, passion fruit and fig were not detected and the relationship between these aromas and other Sauvignon blanc aroma impact components needs to be further investigated. The typical cultivar aroma of Vitis vinitra L. cv. Sauvignon blanc is described as vegetative, grassy, herbaceous, gooseberry-, asparagus-and green pepper-like. These nuances are mainly caused by a specific group of chemical components, namely methoxypyrazines. The most important contributor appears to be 2-methoxy-3-isobutylpyrazine (ibMP), which normally occurs in much higher concentrations in Sauvignon blanc grapes and wines than other methoxypyrazines, such as 2-methoxy-3-isopropyl-pyrazine and 2-methoxy-3-sec-butylpyrazine (Allen etal., 1988;