Anthocyanins and tannins in four grape varieties (Vitis vinifera L.). Evolution of their content and extractability

Abstract

Aims: The knowledge of parameters as the quantity of anthocyanins and tannins present during grape maturation, their evolution during the ripening period and extractability data could improve the management of red wine fermentation and help predict the color of wines.

Methods and results: Grapes from Vitis vinifera var. Cabernet Sauvignon, Syrah, Merlot and Monastrell were harvested in 2002, 2003 and 2004 from a commercial vineyards and their physicochemical characteristics together with the anthocyanin and tannin evolution during ripening were followed. The results showed that differences were found in the evolution of these compounds due to variety and year.

Conclusions: Some of the studied parameters seemed to be clearly related to variety (berry weight and extractability index) and others seemed to be clearly affected by soil and edaphoclimatic conditions. The high extractability index in Monastrell reflects the difficulty involved in extracting their anthocyanins. The short maturation period observed for Merlot grapes and the high seed tannin index could lead to excessively astringent wines.

Significance and impact of the study: This study demonstrate that the ripening period of some varieties (Merlot) in very warm conditions is too short, promoting the rapid accumulation of sugar in the pulp and an incomplete seed maturation that may lead to excessively astringent wines. Other varieties, e.g. Monastrell, show longer maturation period that usually permits pulp and seed maturity to be reached at the moment of harvest. The extractability index seems to be closely related to the grape variety and this is also an important fact to take into account when planning a vinification process.