Synthesis and characterisation of natural colourant microcapsules from Clitoria ternatea flowers

Abstract

Clitoria ternatea (CT), locally known as bunga telang, is traditionally used as a natural food colourant in Malaysia. However, its colour stability is limited due to its high sensitivity to heat. This study investigated the microencapsulation of CT-derived natural colourants using six different polymers, including polymethyl methacrylate (PMMA), carboxymethyl cellulose, sodium alginate, gelatine, acacia gum, and chitosan. The CT flowers were extracted with an alkaline solution (pH 10.5), and encapsulation was performed using in situ polymerisation to facilitate microcapsule formation. The structural, morphological, and size characteristics of the microcapsules were analysed using field emission scanning electron microscopy (FESEM). The results revealed that capsule size varied depending on the polymer used. Among the tested polymers, PMMA microcapsules (1.13 ± 0.12 µm) demonstrated superior uniformity, sphericity, and smoother surfaces with fewer cracks compared to other polymers. Microencapsulation efficiency was further evaluated through ultraviolet-visible spectrophotometry, where PMMA microcapsules exhibited the highest absorbance profile, indicating their potential as an efficient polymer for encapsulating CT extracts. Thus, the microencapsulation of CT extracts, particularly with PMMA, is expected to enhance stability and broaden the application of this natural colourant in food, textile, and pharmaceutical industries.