Grapes monoterpene

These last works were highly significant since, In spite of the abundance of volatiles formed by yeast during fermentation, these non-terpene compounds did not vary systematically among the varieties Furthermore, the yeast metabolites did not mask the distinguishing aroma properties of the grape monoterpenes. 

Voirin, S.G., Baumes, R., Bitteur, S.M., Gunata, Z.Y. Bayonove, C. (1990). Novel monoterpene disaccharide glycosides in Vitis vinifera grapes. J. Agric. Food Chem., 83, 1373-1378. 

Williams, P.J., Strauss, C.R., Wilson, B. Massy-Westropp, R. (1982). Novel monoterpene disaccharide precursors of Vitis vinifera grapes and wine. Phytochemistry, 12, 2013-2020. 

Belancic, A., Gunata, Z., Vallier, M.J., Agosin, E. (2003). (i-glucosidase from the grape native yeast Debaryomyces vanriji Purification, characterization and its effect on monoterpene concentration of a Muscat grape juice. J. Agric. Food Chem., 51, 3083-3091. 

Park, S. K., Morrison, J. C., Adams, D. O., Noble, A. C. (1991). Distribution of free and glyco-sidicaly bound monoterpenes in the skin and mesocarp of Muscat of Alexandria grapes during development. J. Agric. Food Chem., 39, 514—518. 

Voirin, S. G., Baumes, R., Sapis, J.C., Bayonove, C.L. (1992). Analytical methods for monoterpene glycosides in grape and wine. 11. Qualitative and quantitative determination of monoterpene glycosides in grape. J. Chromatogr., 595, 269-281. 

Wilson, B., Strauss, C.R., Williams, RJ. (1984). Changes in free and glycosidically bound monoterpenes in developping Muscat grapes. J. Agric. Food Chem., 32, 919-924. 

Numerous volatiles are released upon hydrolysis of glycoside isolates (1, 13), many of which are presumed to be acting as flavor compounds. Different grape varieties apparently produce glycosides which, when hydrolyzed, release differing proportions of monoterpenes, Cn norisoprenoids and benzene derivatives, as well as other volatiles. However, there is little reliable aroma threshold information regarding many of these compounds, and there has been no systematic attempt to relate the volatile composition of the hydrolysates to their sensory properties. 

An examination of hydrolysates produced by glycosidase enzyme or pH 3.2 acid treatment of reversed-phase isolates frcm juices of "non-floral " itis vinifera vars. Chardonnay, Sauvignon Blanc and Semilion demonstrated that these grapes contain conjugated forms of monoterpenes, C, norisoprenoids, and shikimic acid-derived metabolites. The volatile conpounds obtained hydrolytically from the conjugates were produced in sufficient concentration to permit ready analysis by GC/MS. The products of pH 3.2 hydrolysis have sensory significance when assessed in a neutral wine. The study further develops the precursor analysis approach as a technique to facilitate research into varietally specific constituents of grapes. 

Research over the last few years has revealed that the flavor compounds are not end products of monoterpene biosynthesis in the grape. Oxidative pathways, leading to flavorless polyhydroxylated forms of the monoterpenes, are active in Vitis vinifera. Also, the... 

A second property of many of the monoterpene glycosides is their high reactivity in weakly acid media ( ). Acid-catalyzed hydrolysis at pH 3.0-3.5 of these non-volatile and flavorless glycosidic compounds, can give volatile monoterpenes, sane of vdiich have significant sensory properties. Accordingly, the presence of many monoterpenes found in grapes and wines can be accounted for by non-enzymatic reactions (] ). 

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