Conventional and ultrasound-assisted extraction of anthocyanin from red and purple roselle (Hibiscus sabdariffa L.) calyces and characterisation of its anthocyanin powder

Anthocyanin is widely used in the food industry as a substitute of red synthetic food colouring. Anthocyanins and their derivatives have been listed in the Codex Alimentarius Commission in the European Union as a natural colouring agent with the code E163. Roselle (Hibiscus sabdariffa L.) is considered as a readily available natural source for anthocyanin since it is ubiquitous in Indonesia. Various extraction methods such as maceration, ultrasonic-assisted extraction and microwave-assisted extraction have been applied to extract anthocyanin. In the present work, both maceration (ME) and ultrasound-assisted (UAE) techniques were compared in assessing the extraction performance of two varieties of roselle (red and purple). The effect of solvent types and solute to solvent ratios were also evaluated. The liquid extract was further encapsulated and characterised. The present work demonstrated that UAE was better when compared to ME. Moreover, the purple roselle calyces produced more anthocyanin content than the red calyces. In addition, it was found that water was a better choice of solvent as compared to ethanol. Anthocyanin powder from roselle calyces has average particle size of 4.241 µm and 3.942 µm. The characterisation of anthocyanin powder resulted in the moisture content of 10.29% and 9.67% and solubility of 96.92% and 97.44% for red and purple roselle, respectively. The colour intensity based on chromameter confirmed that the anthocyanin powder having L*, a* and b* values around 42.61-43.91, 24.40-24.79 and 5.56 -7.35, respectively.