Sample preparation grape musts

JD McCord, E Trousdale, DD Ryu. An improved sample preparation procedure for the analysis of major organic components in grape must and wine by high performance liquid chromatography. Am J Enol Vitic 35(1) 28—29, 1984. 

The method of sample preparation for grape proteins analysis should be chosen according to the aim of the study. If grape proteins have to be studied in relation to wine characteristics and technology, it is convenient to start from the so-called free run juice , a material representative of the must, in which the proteins are supposed to be involved in the winemaking process and wine quality. The free run juice is obtained by... 

Figure 1. Scheme of sample preparation steps. 1) grape juice volatiles 2) botrytized (3 strains, 5901/2 5909/1 5899/4) 3) addition of linalool to the botrytized musts 4) addition of linalool to the must. 

However, these workers have noted the ability of monoterpene dlols and triols, which are also present In musts and wines, to act as precursors of volatiles (6) Accordingly, variations In monoterpene abundance between samples could be reflective of the method used in preparing the sample or of the analysis Itself. A similar questioning of the emphasis given to the analytical characterization of grapes and wines based on quantification of free monoterpenes had been expressed previously when the lability of various precursor forms of these compounds was first recognized (18,19). Nevertheless these caveats questioned only the detailed interpretation of the statistical data and the need for appropriate techniques to avoid artefact formation. The fundamental soundness of the correlations remains intact. 

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