The concept of berry sugar loading.

Sugar loading can be defined as the evolution of the quantity of sugar per berry, expressed as mg per berry, from veraison onwards. Veraison corresponds with the onset of fruit ma­ turation. In the grapevine, this fruit maturation starts with an abrupt softening of the berry (within 24 hours). This softening goes hand­in­hand with sugars being actively introduced into the berry (sucrose rapidly hydrolysed into hexoses: glucose and fructose). In red and black cultivars, veraison is characterised, after softening, by skin colouring as a result of the biosynthesis of anthocyanins.