The effects of drying conditions and carrier selection on the production of an antioxidant rich powder

Abstract

The benefits of consuming an antioxidant-rich diet have been discussed widely in the literature and includes anti-cancer effects. Antioxidant-rich, bioactive liquids can be created through extraction from plants. A liquid is not ideal as it may require refrigeration and may have a short shelf life. A bioactive powder is more convenient as it can be stored at room temperature for extended periods. The main aim of this study was to develop a drying method to produce a free flowing and non-sorbing bioactive powder in a repeatable and reproducible manner. Typical of many fruit juices and extracts, the bioactive extract used in this study is a sticky liquid. Due to the stickiness of this material, drying is difficult without the use of a drying aid. Traditionally, high molecular weight materials, such as maltodextrin are used as drying aids to increase the glass-transition temperature of the material so it can be dried into a more crystalline, free-flowing, low hygroscopicity powder. In this study, multiple drying methods and conditions were studied and the efficacy of two carriers was considered. Drying methods utilised included oven, vacuum, freeze, and spray drying and the carriers studied were a natural sugar cane fibre and whey protein isolate. The antioxidant extract that was studied was an aqueous extract of the Rosella plant (Hibscus sabdarifa L.). Oven, vacuum and freeze drying were found to take a relatively long time and had a negative effect on the conservation of antioxidant capacity of the extract. Spray drying was found to be the most suitable drying method, with yields of up to 70%, when drying the extract-natural fibre mixture, and up to 98%, when drying the extract-WPI mixture. An increase in the initial antioxidant content was discovered when spray drying with both carriers, which may be due to Maillard reactions occurring during the drying process.