Comparison and Screening of Extraction Conditions for an Anthocyanin-rich Roselle (Hibiscus sabdariffa L.)
Cheerka Pravalika *
Department of Foods and Nutrition, Post Graduate and Research Centre, P.J.T. Agricultural University, Hyderabad (500030), Telangana, India.
T. Kamalaja
Department of Food and Nutrition, College of Community Science -Saifabad, P.J.T. Agricultural University, Hyderabad (500004), Telangana, India.
P. Janaki Srinath
Department of Food and Nutrition, College of Community Science -Saifabad, P.J.T. Agricultural University, Hyderabad (500004), Telangana, India.
P. Sridevi
Department of Human Development and Family Studies, College of Community Science -Saifabad, P.J.T. Agricultural University, Hyderabad (500004), Telangana, India.
*Author to whom correspondence should be addressed.
Abstract
Natural food colourants are gaining attention as sustainable alternatives to synthetic dyes because of their colouring ability and health-promoting properties. This study compared organic solvent, aqueous, orbital shaker-assisted, and ultrasound-assisted extraction (UAE) methods for the recovery of natural red colour from rosella (Hibiscus sabdariffa L.) calyces. In the organic solvent extraction method, ethanol produced the highest extraction yield (20.00±0.28%) after 4 hours, whereas UAE significantly (p < 0.001) achieved the highest yield (28.67±0.21%) and concentration (21.45±0.3) among the methods. Optimisation of UAE identified 60% ethanol with 2% citric acid and 30 minutes of sonication as the optimum condition, yielding 40.03±0.15% extract at a concentration of 25.8±0.04. The optimised extract had a pH of 2.51±0.06, titratable acidity of 21.77±0.64%, ascorbic acid content of 139.23±3.56 mg/100 g, TSS of 21.47±0.32 °Brix, TPC of 28.82±0.18 mg GAE/g, TFC of 50.03±0.07 mg RE/g, DPPH free radical scavenging activity of 84.31±0.26%, and Hunter Lab values of L* 1.68±0.01, a* 1.18±0.01, and b* 0.15±0.01 (ΔE = 2.81; hue angle = 7.3°), indicating a red colour. The findings demonstrated that UAE using 60% ethanol with 2% citric acid for 30 minutes was an efficient method for extracting natural red colour while preserving bioactive compounds and highlighted its potential as a natural food colourant for clean-label food applications.
Keywords: Natural red colour, rosella calyces, Hibiscus sabdariffa L., ultrasound-assisted extraction, ethanol extraction, citric acid, extraction yield, colour concentration, physicochemical properties, antioxidant activity