Colour Change During Hot Air and Microwave Complementary Dehydration of Naturally Dried Date (Phoenix dactylifera L.) Fruits

Abstract

Both microwave (MW) and conventional drying were analyzed with respect to colour change of obtained date (Phoenix dactylifera L.) fruit powder. The total colour difference (TCD) was considered to quantify the colour change applying the full experience design procedure. Among all coded variables (temperature, time, date piece size and sample weight), only the interaction between drying time (X2) and date piece size (X3) is significant concerning the conventional drying. In MW case, all factors, namely time (X2), date piece size (X3), sample weight (X4), power (X1) and all interactions between factors are significant involving the following model: TCD= 24+3.45X1+2.4X2+3.23X3-3.05X4+1.97X1X2+2.18X1X3-4.15X1X4+0.93X2X3-2.64X2X4-2.02X3X4+0.86X1X2X3-2.73X1X2X4-0.87X2X3X4-2.37X1X3X4.