A colour study in the early stages of fermentation of a Vitis vinifera Tempranillo grape must: a comparative assessment under different climatic conditions

Abstract

Program and abstracts of the In Vino Scientia 2005; Poster 59, page 113. Vinifera Tempranillo grapes were collected in two consecutive crops (2002 and 2003) and monitored in their early stages of fermentation undel real cellar production conditions at EVENA (the Station of Viticulture and Enology of Navarra). Parameters such as pluviometry, day-night contrast temperatures, pH, density, polyphenols, metals (Fe, Cu, Zn and Mn) and several colour variables were measured. A similar pattern was observed for both polyphenols and metals contents evolutions in the two years study, although different absolute values were obtained which correlate to the diverse climatic conditions occurring along the grape growing stages.

Spectrophotometric analysis were carried out of the samples at different fermentation times, and changes in colour were monitored after exogenous addition of certain metals. Metals such as Fe and Cu showed a concentration profile vs. fermentation time that resembles closely those of "blue" and "yellow" absorbances in the same period of feermentation. Shiftings of the maximum wavelenghts took place and the influence of polyphenols over the "brightness" and "red" parameters was checked.