**2.3 Anthocyanin concentration in apple peel and its relation to colorimetric values**

In apples, pigmentation is controlled by the relative concentrations of anthocyanin pigments; the main pigment responsible for the red is cyanidin-3-galactoside (idaein). The anthocyanin concentration of the peels of mature apples of eight "Gala" strains (bright red over yellow background) provided regression coefficients of determination (*R*<sup>2</sup> ) of 0.73 and 0.74 and *P* ≤0.05 for the colorimetric values of a\*/b\* (greater value means higher redness) and hue angle (lower value means higher redness), respectively, as measured with a tristimulus colorimeter [17]. This strong relationship between anthocyanin concentration and chromaticity parameters in apple peel shows good prediction of anthocyanin concentration based on chromaticity values and offers the possibility of using a portable colorimeter for nondestructive estimations of fruit anthocyanin concentration in situ.
