Effect of vacuum impregnation and microwave application on structural changes which occurred during air-drying of apple

摘要: Abstract Apple slices, both vacuum impregnated (VI) with an isotonic solution and non-vacuum (NVI), were dried at 30 50 °C air temperature, without microwave (MW) application (0.5 W/g). MW resulted in increased water-soluble pectin fraction, especially VI samples, ranging from 0.313 to 0.390 (expressed as g galacturonic acid/100 g fresh sample). The slices had a harder texture when dry (water content lower than 10 g water/100 g sample), but softer rehydrated (to saturation): also implied slight increase (about 2 °C) of glass transition temperature ( T ) the NVI samples. In contrast which changes about 4 32 °C water activity increases 0 0.22, ones showed very plasticization effect (mean 40 °C). could be explained by soluble aqueous phase fruit during drying. There was no correlation between mechanical properties .