Aroma grape must

The next step of the biotechnical sequence, yeast fermentation, is of the utmost importance to the chemistry of winemaking as well as to the formation of flavor substances. We have investigated this previously using 14C-tagged compounds (16). Amino acids, for example, enter the yeast fermentation with a quasi biochemical valence with regard to the formation of metabolic side products like alcohols and esters. In that respect, the composition of the fermentation substrate, the grape must, is highly important to the formation of aroma substances by yeasts. 

Thibon, C., Shinkaruk, S., Tominaga, T, Bennetau, B., Dubourdieu, D. (2008a). Analysis of the diastereoisomers of the cysteinylated aroma precursor of 3-sulfanylhexanol in Vitis vinifera grape must by gas chromatography coupled with ion trap tandem mass spectrometry. J. Chro-matogr. A., 1183, 150-157. 

The occurrence of many of these reactions depends on the presence of appropriate precursor in the grape must and together with the concentration of precursor and the ability of the yeast to (i) produce an appropriate extracellular enzyme for non-transportable precursors, (ii) take up the precursor, and (iii) transform the precursor different combinations of yeast and grape variety can lead to small or large differences in the aroma and flavour profile of the wine. 

Esters, not fusel alcohols, actually comprise the most abundant group of volatile compounds in wines Rapp (26) has listed over 300 esters and lactones found in grapes, musts and wines. The esters are largely responsible for the fmity aromas associated with wine (52), especially young wine (27). Of the esters, ethyl acetate predominates by some two orders of magnitude (see 40) however, the low aroma thresholds of a number of the fatty acid ethyl esters makes them of sensory import nonetheless (27). 

Most of the USALLE approaches reported are of the discrete type and use an ultrasonic bath. Usuaiiy a vessei containing the sampie and the immiscibie, acceptor phase is immersed in the transmitting iiquid heid in a bath and the process involves application of US for a preset time, phase separation and repetition of the extraction cycle, if required. With siight differences, this procedure has been used to extract aroma compounds from grape must, wine [3-5], aged brandies and aqueous aicohoiic wood extracts [6], or specific compound famiiies such as monoterpenoids [7] as weii as voiatiles [8] both from wine, pesticides from honey [9] and methyimercury from bioiogicai materials [10]. 

More recently, headspace and HS-SPME-GC/MS approaches for analysis of aroma in must and grape extracts were also proposed (Lopez et al., 2004 Prosen et al., 2007 Sanchez-Palomo et al., 2005 Rosillo et al., 1999). 

Mamede, M.E.O., H.M.A.B. Cardello, and G.M. Pastore. 2005. Evaluation of an aroma similar to that of sparkling wine sensory and gas chromatography analyses of fermented grape musts. Food Chem. 89 63—68. 

Brandy. Brandy is a distikate from fermented juice, mash, fmit wine, or fmit residues. It is distiked at less than 190° proof in such a manner as to produce the taste, aroma, and characteristics generaky attributed to brandy. Fmit brandy is distiked solely from the fermented juice or mash of whole, ripe fmit or from standard grape, citms, or other fmit wine. Brandy distiked exclusively from one variety of fmit must be so designated, except grape brandy which can be identified by the term brandy. Brandy must be matured a minimum of two years in oak barrels, otherwise it must be labeled immature. 

White musts and wines made without maceration contain very low amounts of flavonoids. However, when making white wine from white grapes, skin contact at low temperature is sometimes performed before pressing and fermentation to increase extraction of volatile compounds and aroma precursors. After 4h of skin contact, the concentration of flavanol monomers and dimers in must was increased threefold. Delays between harvest and pressing, especially if sulfur dioxide is added to prevent oxidation, as well as thorough pressing, similarly result in increased concentrations of flavonoids in white musts and wines. " " ... 

The must is then left to settle for 3-4 days at temperature below 8-10 °C. Indeed, contact with the sediment can cause the future Vinsanto to show unwanted aroma deviations and color. In this context, more attention needs to be paid to the settling of the must from botrytised grapes. From the sugars, B. cinerea can produce polysaccharides that can muddy the wine and have inhibitory actions on the metabolism of the yeast, and can therefore contribute to the slowing of fermentation and to the increase acetic acid and glycerol production by the yeast (Tachis, 2003). 

The grape spirits permitted are subjected to rigorous quality standards, performed by the laboratories and tasters panel of the IVDP. Turbidity, color, aroma, and taste are evaluated. Ethyl carbamate, total higher alcohols, acetaldehyde, ethyl acetate, methanol, 2-butanol, 1-buta-nol, allylic acid, and cyanidric acid concentrations are analyzed calcium, copper, and iron contents determined and the alcohol content, total acidity, and density assessed. All must be below designated limits (Regulamento n° 84/2010). 

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