Rapid methods for the evaluation of total phenol content and extractability in intact grape seeds of Cabernet-Sauvignon: instrumental mechanical properties and FT-NIR spectrum.

Aims: The FT-NIR spectrum and instrumental texture parameters were assessed as phenol content and extractability predictors in intact grape seeds. Methods and results: The study was carried out on Cabernet sauvignon seeds from grapes harvested at different advanced physiological stages throughout ripening. Among the instrumental mechanical properties, the seed Young’s modulus of elasticity showed a increase during first four weeks of ripening. This parameter showed also the significant correlation with the phenol content and extractability although with low R coefficient. These correlations highlighted that the springier seed tissues greatly increase the phenol extractability. Nevertheless, the best prediction of the seed phenol content, performed directly on intact seeds, was found using FT-NIR spectroscopy in transmittance mode. The standard error of prediction for total phenol content in conditions simulating the maceration step was less than 8 % while for the phenol extractability was worse. Conclusion: On the basis of these results, the two analytical techniques could be favourably proposed for fast monitoring of seed phenolic maturity. Significance and impact of study: In the wine industry, the phenolic composition of grapes at the picking moment is a key factor determining their quality. The chemical methods for the determination of the seed phenol content and extractability are generally slow because a preliminary extraction is required. Therefore, a rapid evaluation of these parameters could be highly interesting for the oenological sector.