Modeling Multispectral Scattering Profiles for Prediction of Apple Fruit Firmness

Nondestructive measurement of fruit firmness would allow the fruit industry to deliver superior, consistent fruitto the marketplace and ensure consumer acceptance and satisfaction.The objective of this research was todevelop mathematicalmodels to describe the relationship between fruit firmness and multispectral scattering profiles from apples. Scatteringimages were acquired from Red Delicious apples using two different multispectral imaging systems at wavelengths 680 nm,880 nm, 905 nm, and 940 nm with a bandpass of 10 nm. Radial scattering profiles were described accurately by a Lorentziandistribution function with three independent profile parameters. Firmness prediction models were constructed using multi-linear regression against twelve Lorentzian parameters for four wavelengths, and they were verified with separate sets of applefruit. The prediction models gave firmness predictions with the correlation coefficient (r) of 0.82 and the standard errorfor validation (SEV) of 6.39 N for one set of apple samples, and r = 0.76 and SEV = 6.01 N for another set.