Process for the measurement of the hardness and for the selection of agricultural products

Method for measuring the hardness of agricultural products comprising the operations of: - implementing a test program suitable for identifying and selecting one or more indices (S3, S4) which can be measured with a non-destructive test on a respective product/fruit, correlated with the hardness (Du) of the same product/fruit, measured by a respective penetration test; - calculating the coefficients that define the straight line representative of the linear correlation between said indices and the hardness for the respective product. The method is implemented with the operations of: - applying on the product a dynamic force, preferably of impulsive type; - detecting the mechanical reaction through at least a piezoelectric transducer capable of generating an electric signal based on the application or transmission of said dynamic force through the respective kiwi fruit; - analyzing said electric signal relative to the fruit, and measuring the crossing time of said dynamic force through the same kiwi fruit; - calculating the value of the index S4 of said dynamic force through the fruit. It was found that the S4 index has a very significant correlation with the hardness of the respective kiwi fruit, and that the coefficients of the relative correlation straight line are respectively a = -1.5084, and b = 0.0072.