Colour change of seeds from veraison to harvest in Vitis vinifera 'Carmenere'

In order to obtain a good quality wine, grapes should be harvested at optimal maturity. Typically, chemical analyses to determine phenolic maturity are performed by expensive laboratory trials or specialised oenologists; moreover, phenolic measure­ments are often erratic and/or based on the subjectivity of a taster. Recent research has focused on estimating harvest maturity by analysing the colour of grape seeds with computer vision; nevertheless, those programmes have not been used commercially due to lack of accuracy. This work focused on analysing the colour evolution of seed zones during ripening. The aim of this preliminary research was to find colour change within six seed coat zones beginning with veraison and ending at harvest in order to detect patterns related with appropriate harvest time. The methodology included seed preparation, scanning, and assigning a colour to each seed zone based on human colour recognition of digital photos. Three zones of each seed face (dorsal and ventral) were studied. Initial research demonstrates that the colour evolution during ripening differs between zones. The beak had the strongest positive correlation between ripeness and colour change. The chalaza, exterior of the chalaza, and especially the raphe, are seed portions that had low correlation between colour and the passage of time. The green of the karina disappeared from the seed coat at the last moment. The detection of the moment when the ventral beak changes to dark brown and the ventral karina to light brown could be useful in developing a more robust program to detect ripeness by computer vision.