Changes in chemical and physical properties of wild apricot 'Zerdali' during drying

In this study zerdali was dried by hot air and microwave pretreated hot air drying and their effects on some physical and chemical parameters were evaluated. First of all salicylic acid (SA) treatment was applied to fresh zerdali samples to determine the effectiveness of SA on postharvest life of zerdali. In the second part of the thesis frozen and thawed zerdali was dried. For comparison, apricot was also dried in the same conditions. Fruits were dried in a pilot plant tray drier with a constant air velocity of 0.5 m/s at 60°C. 1 minute microwave preheating at 350 W was applied before tray drying for microwave + hot air drying. Drying curves showed only a falling rate period. Diffusion coefficients (Deff) were determined ranging between 2.03×10-8 and 1.81×10-7 m2/s. High Deff values may be result of the structure change during freezing and thawing operations. The fit quality of 6 thin-layer drying models was also evaluated and the best fit results were obtained with the Logarithmic and Two Term models. Effects of drying on fruit quality were determined by using the pH, brix, color, total phenolics and total carotenoid analyses. After drying, all color values were decreased as predicted. Sample type and drying method found significantly effective and SA treatment provide little change on color values. Also zerdali found more conservative than apricot on color values. Total phenolic content of zerdali determined significantly higher than apricot before and after drying. Total carotenoid contents were decreased in all samples by drying.