Color and anthocyanin evaluation of red winegrapes by CIE L*, a*, b* parameters

Abstract

Aims: The aim of this work was to study the color of the wine grapes using the CIELAB parameters and to develop colorimetric indexes which can be used as a rapid method to assess the anthocyanin content of the wine grapes in the vineyard.

Methods and results: L*, a*, b* parameters were measured by a reflectance spectrophotometer on eighteen red winegrapes at harvest. Two indexes were calculated: CIRG2, used as colorimetric index for table grapes and CIRWG (Color Index for Red Wine Grapes). These indexes showed effective potentialities for descriptive, taxonomic and ampelografic studies. Particularly the CIRWG index is more correlated to the total anthocyanin amount, while the CIRG2 is more correlated to the different forms of the anthocyanins.

Conclusion: The colorimetric indexes applied directly in the vineyard permit to assess the total anthocyanin content and to give further quickly information on grape quality and maturity.

Significance and impact of study: The development of analytical methods for the evaluation of anthocyanin immediates, easily applicable, at low cost in the field by grape-growers and winemakers, can be very useful in deciding the harvest date.