Nondestructive Characterization of Apple Firmness by Quantitation of Laser Scatter

A laser technique for characterization of apple firmness was developed on the assumption that laser scatter was affected by firmness. Saturated area ratios and relative areas, defined as laser scatter parameters, were measured for Tsugaru and Fuji apples and the effects of laser wavelengths and optical power levels on the parameters were investigated. When a laser beam with longer wavelength, 632.8 nm, and lower power, 1.7 mW was used, the laser parameters showed significant correlation with firmness parameters. Varietal difference had significant effects on the correlation between different compressive properties and laser scatter parameters. For Tsugaru apple, bio‐yield force and rupture force showed high correlation with laser features, while for Fuji apple, bio‐yield deformation and rupture deformation were more significant than the bio‐yield and rupture forces. The initial slope and secant slope showed high correlation with laser features regardless of cultivar.