Author(s)

Yoshio Makino^1*, Kenjiro Goto¹, Seiichi Oshita¹, Akari Sato², Masato Tsukada²

¹Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
²Data Science Laboratories, NEC Corporation, Kawasaki, Japan.

An objective grading method using a Computer Vision System (CVS) for mangoes is proposed. Red peel was selected using two types of color space values at chroma = 22 and hue angle = 52°. Eighteen out of 25 fully-ripened fruits were graded as “excellent,” determined by the share of red area per fruit being in the range of 80% - 100%. In contrast, all green-mature fruits were graded as “fair,” where the share of red area per fruit was <30%. If the threshold for the share of the red area on the peel is set between 10% (maximal green-mature fruits) and 18% (minimal fully-ripened fruits), automatic removal of green-mature fruits on a grading line is feasible. CVS was effective for nondestructively assuming anthocyanin concentration. A linear relationship between the natural logarithm of the concentration and hue angle was observed (y = - 0.0542x + 7.83), with a correlation coefficient accuracy of 0.94 and root mean square error of 1.31 mg·kg^-1. This result may be effective for the visualization of anthocyanin distribution on mango skin. The threshold for red peel can be in the range of 131 - 186 mg·kg^-1. This suggests that the pigment concentration is usable as a universal threshold. This value is unaffected by conditions for image acquisition or color measurement (e.g., light source, sensor, filter, and optical geometry), unlike color space values as hue angle.

Mangifera indica L., Nondestructive Analysis, Digital Camera, Anthocyanin

Makino, Y. , Goto, K. , Oshita, S. , Sato, A. and Tsukada, M. (2016) A Grading Method for Mangoes on the Basis of Peel Color Measurement Using a Computer Vision System. Agricultural Sciences, 7, 327-334. doi: 10.4236/as.2016.76033.