The present study was designed to investigate effect of spray-drying
as microencapsulation technique on the stability of Roselle calyces‘
anthocyanins. Twelve different extraction conditions were evaluated to
identify the best extraction presider for extracting Roselle anthocyanins.
The results showed that using 2% citric acid solution by 1: 10 solids:
solvent ratio with crushed flower at 85°C for 20min. was the best condition
for extraction of the red pigments from Roselle calyces.. Total phenolic
contents (TPC) and antioxidant activity was determined and the results
showed that Roselle calyces had TPC ranged from 12.16 to 14.45mg. Gallic
acid equivalent/g. Roselle calyces. Methanol: water (80:20) recorded the
highest TPC followed by ethanol: water (50:50) while, distilled water
recorded the lowest TPC of 12.16 mg Gallic acid equivalent/g. Roselle
calyces. Results also reflected that Roselle calyces had a strong antiradical
efficiency of 0.727 and EC50 of 1.37g Roselle extract/g DPPH.
Thermal stability of Roselle anthocyanins was investigated and the
results showed that Roselle extract heated at 70°C for 30min retained
89.01% of their anthocyanin content. With increasing the temperature to
95°C the retention value was decreased and recorded 80.017%,
respectively. The effect of three different encapsulating agents i.e.
Maltodextrin D.E. 18.7, gum Arabic and Whey protein isolate; on pigments
stability was investigated. The degradation followed first – order reaction
kinetics and was strongly dependent on the matrix. Maltodextrin DE 18.7
was found as the most effective carrier in stabilizing the pigments. The
obtained results showed that degradation rate constant values were 5.3, 1.2;
2.2 and 2.6 X 103 for the control, Maltodextrin DE 18.7; Gum Arabic Whey
protein isolate respectively. Half–life period of the encapsulated Roselle
anthocyanins were increased feom130.78 for the control sample to; 266.60;
315.07and 577.62days for Whey protein isolate; Gum Arabic and
Maltodextrin DE 18.7 respectively. The encapsulated pigments were used
as coloring agent in strawberry drink model system and jelly. The results
proved that addition of Roselle anthocyanins at concentration of 0.3 % in
the drink model system and 0.5% to the jelly formulation, as a natural color
was acceptable and can replace the synthetic color.