Scaling up stirring-assisted extraction and transformation of roselle anthocyanins into dried powder using spray-drying and oven-drying

Abstract

Roselle (Hibiscus sabdariffa L.) is a source of anthocyanins with double functions as natural colorants and pharmacologically active ingredients in the food and pharmaceutical industries. Optimizing its extraction by upscaling and engineering the derived extract into its concentrated form or dry powder are thus needed. This study optimized the conditions of stirring-assisted extraction (SAE) of roselle calyces at an upscaled volume, determined the physicochemical and antioxidant properties of extract concentrated with rotary evaporation, and evaluated the effects of spray-drying and oven-drying on the powdered extract characterized from both properties. Results show that anthocyanin extraction from roselle was successfully upscaled using SAE with these optimized conditions: 50 % ethanol acidified with 2 % citric acid as the solvent, an S/L ratio of 1:15 g/mL, and three extraction cycles with a duration of 60 min each. Concentrated extracts (moisture content = 1.38–2.35 %) can be used as an alternative form of storage. Spray-drying with the matrix maltodextrin proved effective in producing dry powder with superior properties than oven-drying. Spray-drying and a 1:1 extract-to-maltodextrin ratio created more favorable dry powder: smooth surface, light red color, amorphous structure, spherical morphology, homogenous particle size (avg. 1.951 µm), total anthocyanin of 2.15 mg/g, antioxidant activity at IC50 = 203.56 µg/mL, and color stability maintained at pH = 2.6–4.0. These conditions enable extraction scale-ups for industrial production. Further, storage in thick concentrations and oven-drying can alternatives in specific cases when spray-drying is not doable.

Keywords

• Extraction scale-up
• Natural colorant
• Oven-drying
• Roselle anthocyanins
• Spray-drying
• Stirring-assisted extraction