Extraction, encapsulation and utilization of red pigments from roselle (hibiscus sabdariffa l.) as natural food colourants [electronic resource].

Includes references.

The present work was carried out to produce a dry powder of red colour from roselle calyces for colouring some food products using microencapsulation technique. The stability of t.he encapsulated pigments was investigated dur¬ing storage under different water activities. The results showed that ethanol acidified with L5N HCI (85:] 5) had the greatest efficiency in extracting roseIle pigments followed by 2% citric acid solution while distilled water was the least effective. The results indicated that at low pH values (1.5,2. and 3), the pigment extracts exhibited their greatest stabilities during the entire holding time. Data showed that roselle pigment extracts heated for 30 min at temperatures of60, 70, 80,90, and 100de, retained 99.87, 99.24, 94.49, 86.35, and 78.59% of their anthocyanins contents, respec¬tively. As heating time was extended to 60 min., the retention values decreased to %.99, 86.75, 82.10. 76.72, and 57.69%, respectively. The effect of three different encapsulating agents i.e. maltodcxtrjn D.E. 10, maltodextrin D.E. 20, and gum Arabic on pigments stability \vas investigated. The degradation followed first - order reaction kinetics and was strongly dependent on a" and the matrix. Among the polymeric matrices, which largely elongated the half¬-life of roselle anthocyanins, maltodextrin DE 20 was found as the most effective carrier in stabilizing the pigments under all storage conditions examined. The half-life periods for anthocyanins encapsulated in maltodextrin DE 20 were 433.1,238.96,80.58, and 94.93 days fbr storage water activities 01'0.43,0.53, 0.64 and 0.75, respectively. Data indicated that addition of encapsulated roselle pigments to straw berry jam (0.1 %) and hard candy (0.2%) resulted in comparable accepted product to controls.

Summary in Arabic.