Grapes elemental composition

The elemental composition of 36 grape samples harvested at technological ripeness from 10 varieties is reported in Figure 8.2. Concentration ranges agree with the other data reported in the literature (Cabanis, 1998 Sponholz, 1989). 

This is the typical Italian grape-based pomace distillate. Produced and kept with a higher alcohol content, before sale it is diluted with water to a content of between 38% and 60% alcohol by volume (usually 42-43%) and filtered. As a consequence of water dilution, haze and turbidity of the product may occur. The elemental composition of grappa is related in particular to the stability of the product -mainly caused by Cu, Fe and related colour changes, and Ca and Mg precipitations with sulphates - and the presence of heavy metals eventually leached by distillation apparatus, tanks and pumps, wooden casks, filter pads and glass bottles. A survey of limpid and apparently stabile 58 grappa samples produced in northern Italy, some processed by very small distilleries, is shown in Table 8.10. The data show that the maximum values of several elements are clearly due to the cited leaching phenomena. 

Greenough, J.D., Longerich, H.P. and Jackson, S.E. (1997) Element fingerprinting of Okanagan Valley wines using ICP-MS Relationships between wine composition, vineyard and wine colour. Aus.]. Grape Wine Res., 3, 75-83. 

It is not uncommon that bacteria do not develop weU even when aU the mentioned parameters are optimal since the composition of wine is very complex. From a nutritional point of view, essential elements such as carbon, nitrogen, vitamins, and metal sources are appropriately represented in the wine. Pentoses and hexoses present after AF, in concentrations of about sevraal hundred mg/1, are sufficient to produce the necessary biomass to carry out the MLF In addition, the bacteria glycosidases and peptidases hydrolyze numerous glycosylated and peptide molecules into sugars and amino acids, which they then use. By contrast, grape molecules, such as some phenohc compounds, may be toxic but they may have positive effects as has also been demonstrated (Theobald et al. 2008 Cairpos et al. 2009). 

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