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Development of spray dried plain and instant powders of roselle (Hibiscus sabdariffa L.)
Thesis Abstract:
The study was conducted to produce spray dried powders of roselle (Hibiscus sabdariffa L.) and assess the effects of spray drying on the proximate composition, physicochemical properties, and microbiological qualities of the products. Spray drying process involved the extraction process, liquid feed formulation, and the actual drying of the liquid feed in the spray drier. The processes involved were established to produce the spray dried instant and plain roselle powders.
Extraction of roselle with 25°C water prior to blending (without pre-soaking) was the most effective in retaining most of the chemical components of the extract. The roselle extract formulated with 80:20:0 and 60:20:20 extract to maltodextrin to sugar ratio, produced the liquid feed formulation for plain roselle powder and instant juice powder, respectively. The spray drier operated at Ti = 175°C ± 1, To = 73°C ± 1, F = 10 rpm, and P = 1.5–2.0 bars.
Spray drying caused significant reduction in proximate compositions of instant and plain powders particularly moisture, fiber, protein, and fat contents; however, ash content was not significantly reduced. On the other hand, carbohydrate content significantly increased when spray drying was used. Spray drying also caused lesser degradation of antioxidant activity, anthocyanin, total phenolics, and vitamin C contents compared with oven drying. Results also showed that plain and instant
powders have acceptable microbial qualities. In terms of sensory characteristics and acceptability, rehydrated instant roselle juice at 1:4 powder to water ratio was the most acceptable. Plain roselle powder and instant roselle juice powder with significant chemical components and high consumer acceptability were developed.
