Vacuum-belt drying of blueberry powders
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Vacuum-belt drying (VBD) was performed on whole blueberry slurry (WBS) and blueberry pomace (BP). The effect of drying temperatures (80°C, 95°C, 110°C), and levels of maltodextrin (0.3, 0.45, 0.6 kg MD/Kg dry solids of blueberries) on physical properties of WBS powders were studied. Increasing MD levels and drying temperatures reduced hygroscopicty and improved powder flowability. Moisture sorption isotherms were well-fit with the GAB model and showed type Ⅲ behavior. WBS powders showed reddish-purple color having lowest L* value at 80°C, and highest C* value at 110°C. BP was dried using different temperatures (80°C, 100°C, 120°C) and methods (batch and continuous VBD). Higher temperatures and continuous drying reduced hygroscopicity of BP powders. BP powders showed good flowability compared to WBS powders. GAB model for BP powders showed type Ⅱ behavior. Higher drying temperatures resulted in lower C* and h°. Batch processed had higher C* and lower h° than continuously processed.