Uva da tavola ipocalorica, possibilità di coltivazione e nuove prospettive di mercato

Abstract

According to the CODEX STAN 255 (2007), table grapes can be harvested when the refractometric index reaches at least 16° Brix. Grapes with a lower refractometric index are accepted provided the sugar/acid ratio (Total Soluble Solids/Tritatable Acidity – TSS/TA) is at least equal to 20:1 if the Brix level is comprised between 12.5° and 14° Brix, 18:1 if the Brix level is comprised between 14° and 16° Brix. Some table grapes grown in Mediterranean climate can accumulate TSS higher than 16° Brix, with low levels of acidity, thus leading to a TSS/AT ratio even greater than 30: 1. Grapes that accumulate TSS less than 12.5° Brix and low TA levels, hardly reach the recommended ratio TSS/TA of 20:1, rather stopping at lower values. Based on these considerations in 2012 an experimental trial of four years started on a total of 103 table grape cvs. Phenological phases in relation to the acidic and sugar content were measured in order to assess the TSS/TA ratio and build regression lines with TSS. Almost all cvs. showed a significant linear regression, with R2 values higher than 0.80 and a standard error between 00.18 and 1.74. TSS values of 103 cvs. at TSS/TA ratio of 20:1, predicted by means of linear regression equations, , were subjected to cluster analysis based on Euclidean Distance. We identified nine clusters, of which the first two with the predicted TSS between 10.04° and 11.77° Brix (7 cvs.) and 12.08° and 12.62° Brix (7 cvs.), respectively. Some of the cvs. showing TSS values below 12.5° Brix at the TSS/TA of 20: 1, were subjected to a test panel of 24 tasters, who were asked to indicate the acceptability of these grapes on hedonic scale of 9 points. Preliminary results showed that for some table grapes with TSS below 12.5° Brix, a SST/AT ratio lower than the recommended 20:1 can be proposed, while preserving an acceptability by the consumer. These results suggest a more modern perspective on grapes nutritional intake, which takes into account the real needs of Western countries where diabetes, hyperglycemia, obesity and cardiovascular diseases are the main dismetabolisms arising from a diet too rich in calories. These grapes thus represent a new frontier and an opportunity for producers of table grapes, who want to enterprise a market share on “grape diet”, and represent a genetic basis for breeding aimed at obtaining new hypocaloric grape cultivars.