The invention relates to use of microalgae for suppressing the production of sugar in grapes during the ripening of the grapes. The invention further relates to a process for growing grapes comprising: a) applying, during the ripening of the grapes, an aqueous composition comprising cells of microalgae and/or an extract of microalgae to the grapes, the leaves, other parts of the grapevines and/or the soil in which the grapevines are rooted and b) harvesting the grapes, and a process for making wine comprising the process for growing grapes.