Comparison of blueberry powder produced via foam‐mat freeze‐drying versus spray‐drying: evaluation of foam and powder properties

BACKGROUND; Blueberry juice powder was developed via foam‐mat freeze‐drying (FMFD) and spray‐drying (SD) via addition of maltodextrin (MD) and whey protein isolate (WPI) at weight ratios of MD/WPI = 0.4 to 3.2 (with a fixed solids content of 5 wt% for FMFD and 10 wt% for SD). Feed rates of 180 and 360 mL h−1 were tested in SD. The objective was to evaluate the effect of the drying methods and carrier agents on the physical properties of the corresponding blueberry powders and reconstituted products.

RESULTS; Ratios of MD/WPI = 0.4, 1.0 and 1.6 produced highly stable foams most suitable for FMFD. FMFD gave high yields and low bulk density powders with flake‐like particles of large size that were also dark purple with high red values. SD gave low powder recoveries. The powders had higher bulk density and faster rehydration times, consisting of smooth, spherical and smaller particles than in FMFD powders. The SD powders were bright purple but less red than FMFD powders. Solubility was greater than 95% for both FMFD and SD powders.

CONCLUSION; The FMFD method is a feasible method of producing blueberry juice powder and gives products retaining more characteristics of the original juice than SD.