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Color Evaluation and Stability Studies of Roselle Extract as a Natural Food Colorant
Ahmed Samir Ali Mahrous, Faculty of Education, Ain Shams University
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. 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. Maltodextrin DE 18.7 was found as the most effective carrier in stabilizing the pigments. Half–life period of the encapsulated Roselle anthocyanins was 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 and 0.5% to the jelly formulation, as a natural color was acceptable and can replace the synthetic color.
Key Words: Roselle anthocyanin, Extraction, encapsulation, stability, Food colors, natural colorant, antioxidant.
Prof. Dr. Mohamed Abass Mohamed.
Dr. Khalid Abdel Hamid Selim.