Quantitative and Instrumental Measurements of Grape Flesh Texture as Affected by Gibberellic Acid Application

To compare the texture of GA3-treated and untreated berries, the deformation at the first major peak (DFP), an indicator of sensory difficulty of breakdown in mastication and the maximum force (MF), an indicator of firmness in a series of puncture tests, were measured using 14 genotypes of American grapes (Vitis labruscana Bailey), European (Vitis vinifera L.) grapes and interspecific hybrids (V. labruscana × V. vinifera). GA3 was applied to clusters of each cultivar at full bloom and 10-16 days after full bloom. While the effect of the GA3 treatment was insignificant for the DFP, GA3-treated berries had a significantly higher MF than the control, indicating that GA3 treatment increased flesh firmness. The genotype × treatment interaction for both DFP and MF was significant, suggesting that the response to the application of GA3 varied, depending on the genotypes. It was possible that GA3 treatment to a cultivar with soft flesh results in a change to crisp flesh (2.5 mm ≥ for DFP and 0.9 N ≤ for MF), which is a desirable texture for table grapes. Soluble solid concentration and titratable acidity in GA3-treated berries were not different from those in untreated berries. Therefore, the effect of GA3 on flesh firmness was suggested to be direct and not the result of a delay in berry ripening.