The determinants of the dried material quality were the color change and the water
activity. Color change was determined as the difference between fresh sample color
value and dried sample color value. Color was measured using colorimeter CR-400
Konica Minolta Sensing, INC. (Japan). The colorimeter was connected to the computer,
equipped with SpectraMagic NX QC software. Before the color measurement,
the sample was grounded in a basic analytical mill IKA A11 (Werke GmbH & Co.
KG, Germany). The color of the potato was indicated by CIELab color scales L, a,
b. The value of total color change (E) was calculated using formula (1).