In addition, thanks to statistical tools, the team has been able to confirm that there is indeed a direct relationship between the aspect and colour of seeds and their phenolic content, with phenols being compounds that determine the ripeness of the grape. This is also the case according to another study published in the 'Analytica Chimica Acta' journal, which obtained its results from La Rioja grapes collected on six separate occasions.
"The compounds analysed in the seeds are not the main causers of red wine colour, but their polymerisation and oxidation during the ripening phase cause browning in the seeds. This was determined using tristimulus colorimetry through digital imaging and is linked with composition," adds another of the authors, Francisco J. Rodrguez-Pulido.
Understanding this relationship "proves useful as a quick and objective estimation method when deciding upon the best time for picking and, therefore, the quality of the wine, without the need for chemical and sensory analyses."
Wine experts tend to use so-called 'technological ripening', based on sugar from juice, as a way of determining when to pick grapes. However, the authors have emphasised that the ripeness of seeds must not be forgotten as this also influences wine quality.
"In warm climates, like that enjoyed in the south of Spain, technological ripening occurs quickly and does not provide enough time for seeds protected inside the grape to develop at the same speed," explains Rodrguez-Pulido, who recognises the need for continued research so that in the future "grapes characteristics shown in their digital 'portrait' can be used to predict the type of wine that they will yield."
FECYT - Spanish Foundation for Science and Technology