EFFECT OF EXTRACTION CONDITIONS, HEAT TREATMENTS AND SPRAY-DRYING ON STABILITY OF ROSELLE CALYCES ANTHOCYANINS AS NATURAL FOOD COLORANTS

Abstract

The present study was designed to investigate effect of spray-dryingas microencapsulation technique on the stability of Roselle calyces‘anthocyanins. Twelve different extraction conditions were evaluated toidentify 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 conditionfor extraction of the red pigments from Roselle calyces.. Total phenoliccontents (TPC) and antioxidant activity was determined and the resultsshowed that Roselle calyces had TPC ranged from 12.16 to 14.45mg. Gallicacid equivalent/g. Roselle calyces. Methanol: water (80:20) recorded thehighest TPC followed by ethanol: water (50:50) while, distilled waterrecorded the lowest TPC of 12.16 mg Gallic acid equivalent/g. Rosellecalyces. Results also reflected that Roselle calyces had a strong antiradicalefficiency of 0.727 and EC50 of 1.37g Roselle extract/g DPPH.Thermal stability of Roselle anthocyanins was investigated and theresults showed that Roselle extract heated at 70°C for 30min retained89.01% of their anthocyanin content. With increasing the temperature to95°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 pigmentsstability was investigated. The degradation followed first – order reactionkinetics and was strongly dependent on the matrix. Maltodextrin DE 18.7was found as the most effective carrier in stabilizing the pigments. Theobtained 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 Wheyprotein isolate respectively. Half–life period of the encapsulated Roselleanthocyanins were increased feom130.78 for the control sample to; 266.60;315.07and 577.62days for Whey protein isolate; Gum Arabic andMaltodextrin DE 18.7 respectively. The encapsulated pigments were usedas coloring agent in strawberry drink model system and jelly. The resultsproved that addition of Roselle anthocyanins at concentration of 0.3 % inthe drink model system and 0.5% to the jelly formulation, as a natural colorwas acceptable and can replace the synthetic color.