Nondestructive assessment of watermelon flesh color by laser vibrometry

Flesh color of watermelon is often used as a major postharvest criterion by consumers to assess fruit quality. In this paper a non-destructive method was studied to determine watermelon (Crimson Sweet) internal color. Responses of samples to excitation vibrations were detected using laser Doppler vibrometry (LDV) technology. Phase shift between input and output vibrations were extracted overall frequency range. The frequencies of phase shifts which had the highest correlation with Hunter color values were selected. Regression models were developed to predict texture color using obtained results. The correlation coefficients of the calibration and cross validation models were 0.9 and 0.86 for a* respectively. Those of L* were 0.91 and 0.87. Meanwhile, cut watermelons were sensory evaluated by subjective scoring of color. Comparisons showed that correlations between objective measurements and consumer opinions were significant at the 0.01 level. This study demonstrated feasibility of laser vibrometery for predicting flesh color of watermelon.