Veraison is the time when the bunches of grapes have almost reached their final size. For the red varieties, the berries will slowly turn purple (the polyphenols responsible for the red color are the anthocyanins). For the other varieties, they will go from green to a pretty golden, translucent color (flavones for these polyphenols there). This period can last between two weeks and a month. During this period, there is an increase in the sugar level in the cluster and the acidity decreases.