Evaluation of Pulp Thickness in Polished Coconut by Color Spectrophotometer

Abstract

This research aimed to apply optical properties of polished coconut shell to predict pulp thickness or maturity. Predictive equations were constructed using 210 polished coconut shell by comparing the uses of reflectance spectra and colour values (L*, a*, b*) together with glossiness. Both reflectance spectra and colour values were obtained by averaging three measured positions at the bottom of coconut shell samples. Predictive equation generated from colour values provided slightly higher accuracy than the one developed from the reflectance spectra, in which, b* was considered the most crucial variable to pulp thickness prediction. When the predicted pulp thickness data obtained from L*, a*, b*, and gloss colour values were used to separate the coconut into 3 grades, it was found that sorting accuracy reached 80.8%, which was higher than the accuracy operated by skilled labours (74%). Results of this research showed the possibility of using colour values to predict pulp thickness or maturity of polished coconuts, which could be further applied as a sorting tool in postharvest supply chain.