Study on anthocyanin in pigmented plants and its application in Malaysian steamed rice cake 'apam kukus' / Siti Azima Abdul Muttalib

The application of anthocyanin extract in foods is gaining interest concurrent with the adverse effect of the synthetic colourants, though the instability of anthocyanin towards multiple food processing limits the application of anthocyanin especially in high-temperature food such as 'apam kukus', a traditional Malaysian steamed rice cake. The main objectives of this study were to investigate the anthocyanin stability, colour properties, phenolic compositions and antioxidants activities of Garcinia mangostana peel, Clitoria ternatea flower, Syzygium cumini fruit and Ardisia colorata var elliptica fruit, as well as their potential application in 'apam kukus'. Antioxidant assays employed in this study were ORAC, FRAP, ABTS and DPPH radical scavenging activity assays. The results revealed that G mangostana exhibited higher in all antioxidant activities tested as well as a potent antimicrobial activity against Aspergillus niger, Bacillus cereus, Bacillus subtilis, and Staphylococcus aureus. C. ternatea exhibited moderate to low antioxidant activities but higher in colour density and indices of polymeric colour. Based on the HPLC results, the decreasing order of total phenolic acid was G. mangostana > A. colorata > S. cumini > C. ternatea; the decreasing order of total flavonoid was G mangostana > S. cumini > C. ternatea > A.colorata and the decreasing order for total anthocyanin content was G mangostana > A. colorata > C. ternatea > S. cumini. Based on the results of HPLC and LC-QTOF, cyanidin 3-glucoside, delphinidin 3-glucoside, and malvidin 3-galactoside is first time identified in A. colorata. The results showed that decreasing the extractant pH resulted in the increased in anthocyanin content and colour density (CD), however, decreased the antioxidant activities of the samples.