Comparison of drying kinetics and texture effects of two calcium pretreatments before microwave-assisted dehydration of apple and potato

The effects on drying rate and texture of treating two plant tissues with calcium, before drying in air with microwave assistance, were studied in this work. The two tissues, potato and apple cubes, which have different structures and composition, were pretreated by immersion in CaCl2 solutions at 20 or at 70 degreesC before microwave-assisted air dehydration at 50, 60 and 70 degreesC. The pretreatments with calcium influenced the strength of the plant tissue cell wall, producing products of varying hardness after rehydration. The effect of the two calcium pretreatments was quite different for apples and potatoes. For apples, calcium pretreatment at 20 degreesC increased the hardness of rehydrated apples compared with untreated apples, but calcium pretreatment at 70 degreesC had no effect on texture. For potatoes, both calcium pretreatments at 20 and at 70 degreesC significantly increased the hardness of rehydrated potatoes. The water diffusivity during drying varied mainly because of the type of plant tissue, with secondary effects caused by the drying temperature and the type of calcium pretreatment.