A Grading Method for Mangoes on the Basis of Peel Color Measurement Using a Computer Vision System
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Date
2016-06
Journal Title
Journal ISSN
Volume Title
Publisher
Scientific Research
Abstract
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.
Description
Keywords
Mangifera indica L., Nondestructive Analysis, Digital Camera, Anthocyanin
Citation
Agricultural Sciences, 2016, 7, 327-334