Effects of freeze-drying and powder storage time on preservation of bioactive compounds and antioxidant activity of mixed pineapple (Ananas comosus) and acerola (Malpighia emarginata) pulps

Pineapple has high emulsifying capacity and acerola has high healthy bioactive compound levels. The mixture of these fruits can be used in the preparation of functional powdered beverages through freeze-drying. Physicochemical, rheological, thermal and colorimetric parameters and bioactive compounds were measured and the microstructures of the powders were visualized by scanning electron microscopy. The freeze-dried pulps had an attractive color, high hygroscopicity (>27 g/100 g), low water activity (≤0.334 ± 0.009), glass transition temperature ranging from 1.46 to 3.89 °C and microstructure strongly porous. Both fresh and rehydrated mixed pulps showed the rheological behavior of a non-Newtonian pseudoplastic fluid. The pineapple pulp:acerola pulp ratio influenced significantly the variables analyzed. Higher contents of bioactive compounds (ascorbic acid, total phenolic, anthocyanin, antioxidant activity) after freeze-drying and storage were obtained increasing concentrations of acerola. Under the storage conditions used, no synergistic effect that allow to control of ratio among fruit pulps that better preserving the powder nutritional properties.