Nondestructive and noncontact measurement of flesh firmness of 6 apple cultivars by Laser Dopplar Vibrometer (LDV)

For the investigation of non-destructive measurement of fruit firmness, 6 cultivars of apple fruit were stored at 20degreesC after harvest. Every week, using 5-10 fruits, the frequency of second resonance of individual fruit were measured by a Laser Doppler Vibrometer (LDV) non-destructively, and the elastic indexes were calculated with the second resonance and fresh weight. Thereafter, the flesh firmness was measured by ordinary destructive method with the Magnes-Taylor fruit firmness tester. From the correlation coefficient between the elastic indexes and the firmness, the possibility to measure the flesh firmness of 6 apple cultivars by LDV method was evaluated. As the result, in 'Natsumidori', 'Iwai', 'Tsugaru' and 'Starking Delicious', the correlation coefficients were over 0.89, a practical possibility of this method was suggested. In 'Fuji' and 'Golden Delicious', however, the correlation coefficients were lower than 0.73, and 0.66, respectively. In these two cultivars, further analysis on this method are proceeding for the practical application.