For vines, grapes are a vehicle to spread DNA so that they may perpetuate the species and colonize new locations. Co-evolution of grapes alongside birds and mammals has resulted in a mutually beneficial exchange. Animals receive a nutritious and delicious fruit snack as ‘payment’ for dispersing the digestion-resistant seeds within, and the seeds, effectively transported away from the parent vine, are conveniently deposited in fertilizer after passing through animals’ guts.
Véraison heralds the start of the ripening process, which is brought about by the expression and repression of hundreds of thousands of genes. At this time, berries begin their transformation from hard, green, and bitter, with enamel-stripping acidity, to aromatic, sweet, attractively colored, and pleasantly acidic.
Grapes start to accumulate sugars, proteins, anthocyanins, tannins, and flavor and aroma compounds, and metabolize acids and increase pH. The entire process is brought about by the expression and repression of hundreds of thousands of genes. The changes during this time heavily influence the final quality and composition of the fruit at harvest. Physical changes include:
Source: Cornell University