Twenty representative tubers from each field replicate were
randomly chosen for instrumental colour measurement. A cylinder
of 16 mm in diameter was cut longitudinally from each tuber, and
further cut into two small cylinders of 10 mmin height, which only
contained flesh tissue. Twenty cylinders were analysed raw, while
the remaining twenty were boiled as described in section 2.2, and
left to cool to room temperature before analysis. Colour was measured
using the CIELAB system of a Minolta spectrophotometer
(CM 600d, Minolta, Osaka, Japan) equipped with an aperture of
8 mm.