Chemical and physical properties of vacuum-dried red beetroot (Beta vulgaris) powders compared to other drying methods

摘要

Beta vulgaris L. powder is commonly used as a source of natural red color in foods. Traditionally, this powder is made by spray-drying or tray-drying, both dehydration methods that involve high temperatures and may lead to degradation of betalains. The objective of this study was to compare physical properties and betalain content of beet powders prepared by tray-, freeze-, drum-, and continuous vacuum-belt drying. Powders prepared by freeze-drying had smaller particles (10-20 mu m) and were more uniform. Those prepared by tray and vacuum-drying were larger and more irregular. Samples prepared with maltodextrins were lighter in color. Those produced by freeze- or vacuum-drying had greater color saturation. All powders flowed, but those prepared by tray- or vacuum-drying flowed more quickly. Freeze-dried and vacuum-dried powders had the greatest betanin content (261-306 mg betacyanin/g dry beet solids) and betaxanthin levels (129-159 mg vulgaxanthin/g dry beet solids), while the tray-tried and drum-dried powders had the lowest levels. Thus, vacuum-belt drying could be used to produce a continuous stream of beet powder with color and betalain content similar to that of freeze-dried product, but in a much shorter time.