Optimization of Malabar Nut (Justicia adhatoda L.) Leaves’ Phenolic Compounds by Alginate Emulsion-gelation Approach using Response Surface Methodology

Abstract

Background: The encapsulation technique is an effective method for coating bioactive molecules and protecting them against various technological treatment conditions during production processing. Objective: The aim of this study was to optimize the encapsulation conditions of phenolic compounds extracted from Malabar nut (Justicia adhatoda L.) leaves by alginate emulsion-gelation approach using response surface methodology Methods: The ionotropic gelation method was used to encapsulate the phenolic compounds of Malabar nut (Justicia adhatoda L.) leaves. The optimization of this phenolic compounds encapsulation was carried out using response surface methodology through Box˗Behnken design. Four parameters with three levels (-1, 0, +1) were chosen including sodium alginate concentration (2 – 3 - 4%), calcium chloride concentration (4 - 6 - 8%), plant extract-alginate solution ratio (0.02 – 0.11 - 0.2 mg/ml), and gelation time (5 – 12.5 - 20 min). of the total phenolic and flavonoid contents encapsulation efficiency was assessed. Likewise, the antioxidant activity was evaluated using ferric-reducing power (FRP) and free radical scavenging activity (DPPH). Results: The results of response surface methodology analysis using Box˗Behnken design showed that the optimal encapsulation conditions were 3.11% for alginate concentration, 5.74% for calcium chloride concentration, 0.1 mg/ml for the plant extract-alginate solution ratio, and 10.80 min for gelation time. Under these conditions, the optimum values of total phenolic and flavonoid encapsulation efficiency were 86.17% and 75.69%, respectively, 126.75 mg AAE/100 g for ferric reducing power and 97.29% for DPPH. The experimental and prediction results have expressed a high significant level for all responses. Conclusion: The method revealed the validity of elaborated models through response surface methodology optimization processes for phenolic antioxidants encapsulation of Malabar nut (Justicia adhatoda L.) leaves extract.