Esterification of anthocyanins isolated from floral waste: Characterization of the esters and their application in various food systems

Abstract

Anthocyanins were extracted from red rose petals collected from floral waste, and were esterified with fatty acids using the lipase Fermase CALB™ 10000 to enhance their lipophilicity. The process parameters for the extraction of anthocyanin were optimized for extraction time, nature of the solvent, substrate to solvent ratio, and concentration of citric acid. Anthocyanins were purified using resins. Acylated anthocyanins were primarily detected using TLC followed by confirmation using LC-MS analysis. Optimization of the reaction parameters was carried out by one-factor-at-a-time method using HPTLC. An optimized molar conversion of 63% of anthocyanins to its fatty acid esters was achieved in acetonitrile at 40 °C with a cyanidin:lauric acid molar ratio of 1:100 and an enzyme and molecular sieve load of 20 mg/mL and 100 mg/mL, respectively, in 24 h. The antioxidant activity of anthocyanin and its fatty acid esters assessed using DPPH, ABTS and FRAP assays showed retention in the activity upon acylation. The use of lauric acid esters of anthocyanins was studied as a colorant in emulsion-based foods such as cupcakes and sandwich biscuit cream (filling). The antioxidant effect of the esterified anthocyanins assessed by TGA, manifested improved stability on the thermo-oxidative lipid peroxidation of the biscuit cream. Anthocyanins and its fatty acid esters were also studied as pre-extrusion colorants in rice extrudates, where the esters showed superior color stability to thermal processing in comparison to anthocyanins. Anthocyanin fatty acid esters can thus find application in functional foods.