Influences of Drying Medium and Inlet Temperature on Properties and Surface Characteristics of Spray‐Dried Powders From Pumpkin‐Based Carotenoids Oil‐in‐Water Emulsion

Oil-in-water emulsion containing carotenoids can be processed into natural yellow colorant powder via spray drying. However, spray drying, which typically employs hot air as drying medium, often causes pigment degradation. Here, superheated steam was for the first time tested as alternative medium to spray dry pumpkin-based carotenoids emulsion; results were compared with those obtained using hot air as conventional medium. Air-dried powder exhibited higher yields, lower moisture contents, and water activities compared to steam-dried powder. Air-dried particles were larger and had smoother surfaces. In contrast, steam-dried particles were smaller and exhibited wrinkled surfaces, which contributed to higher bulk density and faster reconstitution. Confocal laser scanning microscopy revealed that surfaces of air-dried particles were densely covered with carotenoids, while that of steam-dried particles had lower amount of such compound as a result of steam pushing back hydrophobic carotenoids into particle matrix, resulting in higher carotenoids retention and more intense yellow color of latter powder. Increasing medium temperature resulted in higher yields for both powders, whereas moisture content, water activity, bulk density, and reconstitution time decreased. Carotenoids retention decreased with increasing temperature, particularly in air-dried powder, which was associated with more extensive color fading.