Drying kinetics and texture effects of calcium treatment before microwave assisted dehydration of apple and potato
L. M. AHRNÉ1, F. Prothon, T. Funebo, and T. Ohlsson. (1) Environmental and Process Engineering, SIK- The Swedish Institute for food and biotechnology, Box 5401, Gothenburg, S-402 29, Sweden
Calcium chloride has been successfully used by the industry to control softening of fruits and vegetables caused by thermal processing. However, the amount of calcium required to improve the texture of a given plant tissue is determined based on trial-error experiments. Moreover, calcium may improve the texture of one sort of plant tissue and have no effect on other sorts.
The purpose of this work was to determine how two calcium pre-treatments: calcium infusion during low temperature blanching (70°C) and calcium infusion at 20°C, affected the drying rate and the texture of fruits and vegetables. It was also of interest to find out whether the differences in the structure and composition of the plant tissue would influence the effect of calcium on the drying rate and strengthening of the cell walls.
Potatoes and apples cubes were either infused in a CaCl2 solution at 70°C or at 20 °C before microwave-assisted air dehydration at 50, 60 and 70°C. The water content of the potato and apple cubes was monitored during drying, and the texture of rehydrated product was measured by a puncture test using a Texture Analyser.
The pretreatments with calcium influenced the strength of the plant tissue cell wall, producing rehydrated products of varying hardness. Calcium infusion at 20°C increased the hardness of rehydrated apples, but at 70°C had no such effect. Infiltration of calcium either at 20°C or 70°C significantly improved the texture of rehydrated potatoes. The water diffusivity during drying varied mainly with the type of plant tissue.
Our results showed that the temperature at which calcium is infused into the plant tissue has a significant effect on texture, and the mechanisms of calcium in preventing softening seem to be different in potatoes and apples. Further research is necessary to understand and control the texture by calcium addition.
Session 96, Fruit & Vegetable Products