SPECTROPHOTOMETRIC STUDY OF BRUISES ON WHOLE, 'RED DELICIOUS' APPLES

Abstract

ABSTRACT Spectrophotometric studies were conducted to investigate the diffuse reflectance in the 400 to 1000 nanometer (nm) wavelength region for bruised and nonbruised areas on whole 'Red Delicious' apples. Reflectance single-wavelength, two-wavelength ratio, two-wavelength difference, normalized two-wavelength difference, and reflectance derivative models were developed from the reflectance spectra data. Linear regression analysis was used to identify the wavelengths most related to bruise identification for each model. Resulting models were tested using 200 measurements from 50 apples of which 100 were bruised and 100 were nonbruised areas. The single wavelength model had the lowest correlation (r^ = 0.46) and the worst classification performance (50% misclassified) while the ratio, normalized difference, and the derivative models had the best performance (r^ = 0.79 - 0.81), with only 2.5 - 3.5% of the fruit misclassified.