Comparative Evaluation of Different Pretreatments on Tomato Slices Dried in a Cabinet Air Drier.

Effects on drying and other acceptability parameters when slices of tomatoes were subjected to different pretreatments before initiating the process of drying were studied. The study also included observation of effects of inherent moisture levels in the drying tomato on the attributes such as color, texture, shrinkage and appearance. The pretreatments consisted of solutions in water, of sugar (1%), calcium chloride (1,2 % ), common salt (2%), ascorbic acid (0.75%) and sodium benzoate (0.1%). The slices of tomato, 1 cm thick, were soaked in the specific solutions separately for 3, 6 and 12 hours. Untreated tomato slices served as control. Drying was stopped when tomato slices attained moisture levels of 30% and 10%. Drying rate (mr = m ebx where: mr - moisture ratio; m - model constant; b - drying rate; x time, minute) ranged between -0.007 (sugar solution 1%) and -0.029 (control). Pretreatments did in fact influence the shrinkage both at 10 and 30 % moisture levels. Effect on shrinkage was more pronounced at 30 % than 10 % moisture level. Visual assessment and photographs suggest that pretreatments with calcium chloride and sodium chloride had better texture and visual appeal than other pre-drying treatments. Duration of drying to reach 10% moisture level ranged between 180.0 and 241.67 minutes. Variations were observed between samples for parameters re-hydration ratio and water activity (0.462 0.550). It is suggested that pre-drying treatments do affect the different parameters that were studied and can help in improving the visual appeal and acceptability. [ABSTRACT FROM AUTHOR]