Abstract
This investigation was performed on the drying modelling of white sapote slices that were influenced by drying methods and pre-drying treatments. The experimentation was performed by two factors: drying techniques and pre-drying treatments. The drying techniques included oven-, solar- and open sun-driers, whereas the pre-drying pretreatments were blanching, sodium metabisulfite, sodium-chloride and control. Behaviours of the drying were plotted with the moisture ratio vs time of drying, moisture content (% db) vs time of drying, and drying rate (g of water/100 g dm/hr) versus drying time (t). At the commencement of the drying progression, the drying rate was increased steadily and reduced through the advancement of drying model parameters a and n (empirical constants) and k (drying rate constant) were determined. Their combinations were optimised to suit the requirements of the minimal value of the sum of square deviation on the expected data values (model values). The models were evaluated with the regression coefficient (R(2)) and chi-square (χ(2)), resulting in values of 0.95-0.99 and 0.000132 to 0.00511, respectively. Henderson and Pabis's model demonstrated the highest coefficient R(2) values (0.99) for oven-dried drying techniques. Also, the Page model gave the highest R(2) value (0.99) for sodium metabisulphite pretreatments. It can be concluded that the Henderson and Pabis model is best suited for oven drying among the drying techniques. In contrast, the Page model best fits sodium metabisulphite among the pre-drying treatments. Hence, Henderson and Pabis, and Page models might describe the drying characteristics of the white sapote fruit slices based on respective drying methods and pre-drying treatments.