An ultra-low pressure pneumatic jamming impact device to non-destructively assess cherimoya firmness

The quality of cherimoya fruit is reduced by the rapid deterioration of firmness during ripening. Different methods have been developed for the measurement of firmness. The objective of this study was to use a developed impact prototype for the non-destructive assessment and prediction of cherimoya fruit firmness. The prototype has an ultra-low pressure pneumatic jamming rod used to copy the irregular fruit shape. A sample of 200 cherimoyas from Malaga (Spain) ‘Fino de Jete’ were tested during 4 days. Every day all the fruits were non-destructively tested and a set of 15 were destructively tested. On the fourth day all the remaining fruits were also destructively tested. The prototype was capable of copying the irregularities of the fruit and non-destructively assessing the decrease in cherimoya firmness during ripening without causing damage. A high correlation was found between destructive firmness and non-destructive variables from the prototype. A PLS model was developed to relate destructive firmness from day 4 to non-destructive variables and diameter from day 3, with a R 2 of 75.6 and a RMSECV of 0.9885. A calibration set confirmed the prediction with a R 2 of 80.2 and a RMSEP of 0.0561. Firmness decay could be non-destructively predicted 24 h in advance using the variables extracted from the prototype device signal.