Predictive measurements of pigmentation index and polyphenols in olive fruits using a colorimetric approach

The present study evaluates the relation between pigmentation index, polyphenols, and quick colorimeter indexes measurements in olive (Olea europaea L. cv. ‘Cipressino’) fruits. A simple linear regression model was fitted among polyphenols and each of colorimeter indexes to determine which one had better predictive power. Results shown that Hue is positively correlated with the pigmentation index measured by expert operator. Among the 24 polyphenols analyzed, five (cinnamic acid, vanillic acid, verbascoside, oleacein, and 4-coumaric acid) correlate with colorimeter indexes such as Chroma, and Hue. These two indexes are related to color saturation and vividness of the color. In particular, verbascoside vs Hue (R
²
=0.597) and oleacein vs chroma (R
²
=0.675) showed the highest determination coefficients. The error rates of the models are in a range between 7-17% following the order cinnamic acid > 4-coumaric acid > oleacein > vanillic acid > verbascoside.