For the manual inspection, colour values of the surfaces of
banana peels were measured using a colorimeter (CR-400, Minolta
Co., Osaka, Japan) calibrated using a standard white plate
(L⁄ = 97.79, a⁄ = 0.38, b⁄ = 2.05). Each sample was measured 20
times. The colour values ranged from 0 to 100 (L⁄ value), and from
128 to 127 (a⁄ and b⁄ values).