Characterization of some physicochemical properties of spray-dried and freeze-dried sour cherry powders

The main goal of this study was to compare glass transition temperature (Tg)- a(w) relations, critical water activity (a(wc)) values, particle morphology, moisture sorption behavior, total phenolic content, and stability of freeze-dried (FD) and spray-dried (SD) sour cherry powders. The Tg of the SD and FD powders decreased from 57 degrees C to 14 degrees C and from 47 degrees C to 15 degrees C, respectively, as the a(w) increased from 0.03 to 0.35. Higher Tg values were observed for SD powder compared to FD powder in the a(w) range (0.03-0.35) covered in this work. The a(wc) was 0.29 for SD powder and 0.26 for FD powder. Scanning electron microscopy images showed that FD sour cherry powder exhibited a more porous morphology compared to SD powder. Total phenolic content of SD and FD powders was found to be similar (16.1 +/- 0.3 mg GAE/g sour cherry dry matter). The results of this study suggest that physicochemical properties of spray-dried sour cherry powders are comparable to those obtained by freeze drying.