تغييرات ميكروسكوپي ، ويژگي هاي بافتي و ظرفيت جذب مجدد آب برش هاي سيب خشك شده با روش هاي مختلف

Microstructure, Texture And Rehydration Changes in Apple Slices, Subjected to Drying by Combined Coating, Air and Microwave Dehydration

In this study, effect of coating, air and microwave drying on texture, microstructure and rehydration characteristics of Golden Delicious apple slice (22mm diameter and 4mm thickness) was evaluated. Thermal blanching by hot water (80°C. 1 min) was employed to prevent undesirable enzymatic reaction and to improve the porous structure. Coating method by starch (suspension), pectin and CMC solution (2% wlw) with and without CaC12 was used to induce a porous structure during microwave treatment. Rehydration in distilled water was studied. A puncture test and scanning electron microscopy (SEM) were used to analyze effects of these processes on texture and microstructure. Results indicated that employment of coating; air drying (70°C, 1mrs) and microwave treatment (300W, 10s) leads to the production of puffed and porous products. Microscopy evaluation showed that microstructure in samples coated by starch and pectin with CaCl: was improved. Coating had a beneficial effect on microstructure of samples following microwave treatment. Microstructural studies showed an increase in thickness of cell wall after coating treatment by pectin, but thickness of cell wall was not affected by starch and CMC. Using microwave treatment increased rehydration capacity in samples, but reduced texture strength following rehydration. Use of CaC12 improved microstructural properties and prevention of center heating phenomena.