Dados do Trabalho

Título

COMPREHENSIVE TWO-DIMENSIONAL LIQUID CHROMATOGRAPHY ASSOCIATED WITH DIODE ARRAY DETECTOR (DAD) AND TANDEM MASS SPECTROMETRY TO EVALUATE THE ANTHOCYANIN CONTENT DURING GRAPE RIPENING

Introdução

The typical phenolic profile in grapes is characterized by its complexity both in terms of number of diverse chemical structures and their variation during ripening. Besides, grape polyphenol composition at harvest time directly influences wine quality, contributing to organoleptic characteristics, namely color, flavor, astringency and bitterness. In this context, a new method based on the application of comprehensive two-dimensional liquid chromatography (LC × LC) coupled to a diode array detector (DAD) and tandem mass spectrometry (MS/MS) was developed to characterize the phenolic profile of Malbec grapes with different degrees of ripeness.

Material e Métodos

Grape samples were collected from a vineyard located at Garanhuns city (Pernambuco, Brazil) weekly (during 10 weeks) from the phenological stage véraison (berry softening and colouring begins), totalizing 10 samples: W1, W2, W3, W4, W5, W6, W7, W8, W9 and W10.

Resultados e Discussão

Main detected compounds in grape samples were anthocyanins (11), with malvidin derivatives being the most abundant. A good number of polymeric flavan-3-ols (5) were also tentatively identified, among other compounds (p-Hydroxybenzoic acid and (Epi)gallocathechin-(epi)catechin).

Conclusão

Most of the anthocyanins showed a similar trend; their initial content is low (especially at W1 and W2) and then grows to a maximum at W5-W6, followed by a decrease from week 7 and stabilization in weeks 9 and 10. Anthocyanins were found to accumulate in the skin of red berries starting from véraison and reach their maximum in the latest phases of berry ripening when the synthesis decreases or stops. The reduction observed after the seventh week may be related to degradation reactions of anthocyanins in advanced stages that occur due to the exposure of grapes to high temperatures, as observed in tropical viticulture regions. The two-dimensional approach was demonstrated to be a powerful tool for the characterization of the complex phenolic profile of these samples, involving more than 40 different structures and has the potential to be further applied to the study of this important fraction in different grapes and wines systematically.