Sugar is accumulated during ripening. The amount of sugar depends on the length of ripening and crop management practices. Sugar content increases towards maturity, while grape acidity decreases over the same period.
A good oBrix/acid ratio is 25:1 or above, though certain varieties are marketable with brix/acid ratios as low as 20:1. Brix/acid ratio of 20:1 is accepted as the normal standard for most varieties in Europe.
Nitrogen is needed to produce better quality berries; it enhances growth and development of the crop. Application of nitrogen fertilizer resulted in higher sugar content of table grape berries.
Potassium influences the flavour and taste of table grapes by increasing the sugar content and sweetness of the berry as measured by the TSS:Acid ration. Application of potassium fertilizer resulted in increase of sugar/acid ratio of table grape berries.
Foliar boron also helps improve grape quality by increasing the TSS content and reducing acidity of table grapes.
Optimum levels of iron increased TSS contents in grapes according to Indian research. Iron is essentially required for early leaf production and photosynthesis to ensure better berry development and quality. Supply of sufficient amount of iron fertilizer resulted in an increased sugar content.
