Vacuum impregnation and drying of calcium-fortified pineapple snacks

Abstract

Impregnation methods combined with drying (convective- or freeze-) were used for producing calcium-fortified pineapples snacks. Three impregnation alternative were evaluated: I) at atmospheric pressure for 20 min; II) applying 10 min of vacuum (13.33 kPa) to a container with pineapple samples immersed into the impregnating solution followed by 10 min of impregnation at atmospheric pressure; and III) applying vacuum impregnation followed by vacuum pulses (6.70 kPa) after removing the samples from the impregnating solution. The impregnating solution concentration was 1 g Ca2+ 100 ml−1 prepared with CaCl2. The influence of the impregnation method on the kinetics of convective-drying and on porosity, shrinkage, glass transition temperature, water sorption isotherms, texture and microstructure of convective-dried and freeze-dried pineapple samples were determined. After drying, vacuum-impregnated products presented 91% higher concentration of Ca2+ than pineapples impregnated at atmospheric pressure (equal total processing time). Calcium chloride impregnation increased the drying rates and positively influenced the physical properties of the convective-dried product. The combination of vacuum impregnation and drying is a suitable way for the production of calcium-fortified pineapples, which are porous-and-crunchy, with high glass transition temperature favouring its preservation during storage.