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

Abstract

The main goal of this study was to compare glass transition temperature (Tg)– aw relations, critical water activity (awc) 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°C to 14°C and from 47°C to 15°C, respectively, as the aw increased from 0.03 to 0.35. Higher Tg values were observed for SD powder compared to FD powder in the aw range (0.03–0.35) covered in this work. The awc 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. Practical applications Stability of fruit-based powders is mostly determined by their Tg and awc values. Such data are scarce for sour cherry powders. The present study provides useful information on Tg and awc of sour-cherry powders produced with two drying methods. The results of this study clearly demonstrated that properties of spray-dried sour cherry powders compare favorably with those obtained by freeze drying. The findings of this study can be useful in determination of storage conditions for commercial sour cherry powders based on the awc values.