Selection of a mechanical property for the flesh firmness of table grapes in accordance with an OIV ampelographic descriptor.

Flesh firmness is a sensory characteristic proposed by OIV as an ampelographic descriptor for grape varieties and Vitis species (Code-N° OIV 235). To accurately define the flesh firmness of table grapes, an instrumental texture parameter that makes it possible to classify the five reference table-grape cultivars according to this descriptor was selected. The mechanical properties of the berry flesh were determined by texture-profile analysis and cutting tests. The results showed that the berry hardness and gumminess, normalized by the berry diameter, are accurate instrumental indicators of the flesh firmness because the variations among the cultivars were evident, independently of the berry size and the maturity grade. The interquartile ranges of the berry hardness normalized by the berry diameter for each flesh-firmness group established by OIV (soft, slightly firm, very firm) were 0.074-0.117, 0.121-0.158 and 0.205-0.391 N/mm, respectively. This standardized protocol can be applied to better compare the performance of grape varieties.