Indices of Maturity for Table Grapes as Determined by Variety

To determine the suitable time for harvesting grapes for export, the percentage of soluble solids (mostly sugars), total acid, and the sugar/acid ratio of three varieties of table grapes — 9Queen of the Vineyards9, 9Sultanina9 and 9Perlette9 — were evaluated in relation to taste. Berries segregated into maturity levels on the basis of specific gravity (soluble solids) were rated as to acceptability by an experienced taste panel using a descriptive judging scale. It was not possible to establish a single criterion for all the varieties tested. Suggested is, that table grape varieties can be divided into three groups: 1) for varieties low in acid content, such as 9Queen of the Vineyard9, harvest can be scheduled on the basis of the total soluble solids (°B) content; 2) for high-acid varieties, such as 9Sultanina9, acidity alone can be the primary factor for determining harvest; 3) for varieties with medium acid content, such as 9Perlette9, both total soluble solids and acid content should be taken into account when fixing the harvest date. In no case was the total soluble solids acid ratio found to be suitable as a reliable index of maturity.