First study on technological maturity and phenols composition during the ripeness of five Vitis vinifera L grape varieties in Morocco

The time of the maturity and the picking of the grapes remains one of the most important parameters to obtain high grapes or wine quality. Harvest decision is taken traditionally by viticulturists only after sugar, acids, degrees Brix and pH of grapes overlooking the phenol maturity despite they are valuable parameters in determining the quality of table grapes. In this work technological maturity (sugar/acidity) and phenolic maturities were investigated during grapes ripening varieties. Three of them are allochthonous (triploids: Superior, Early sweet and Flam) while two are autochthonous (diploids: Abbou and Adari). The varieties samples were investigated by 12 parameters which three are morphological: weight, density (rho) and the form coefficient (Cs), while 10 other are physicochemical related to the quality proprieties: degrees brix, titratable acidity, pH, juice content, water content, capacity of rehydratation, phenols, flavonoids and tannins compounds. A PCA analyze to classify grapes ripeness according maturities factors were performed. The descriptive quality panels showed that both maturities of the attributes grapes were different among varieties of samples (P <= 0.05). The phenol compounds decreased for the triploid varieties during ripeness whereas they increase in the diploids. The morphological proprieties: weight and density increase in parallel to the degrees brix, juice content accompanied in the other hand by the acids content. The statistics established that the variation of quality factors generally and maturity index (degrees brix/acidity) especially was influenced by the phenol compounds, stage of ripeness or their interaction according to grape varieties. Thus revealed that the phenol compounds, the ratio of sugar/acidity remain the principal attributes determinant the ripeness of grapes.