Optimization of foam mat drying for producing high-quality butterfly pea flower (Clitoria ternatea L.) extract powder

The high anthocyanin content of butterfly pea flowers ( Clitoria ternatea L.) can provide natural antioxidants for use in food and medicine. However, the use of butterfly pea flower (BPF) extract is limited by the instability of its anthocyanins during transformation and storage. Therefore, to convert the liquid BPF extract into a dry powder, we propose the foam mat drying (FMD) process. The dry powder form will improve the stability of the extract and ease handling during storage and distribution. In this method, bioactive compounds in the liquid extract are coated with biopolymers to form foam elements, which are then converted into powder. This study adopts an experimental multi-objective optimization approach, in which drying efficiency, physicochemical quality, and anthocyanin stability are evaluated simultaneously by systematically varying formulation composition and drying temperature, rather than relying on mathematical optimization models. Such an integrated evaluation is still rarely addressed in previous FMD studies, which typically focus on individual quality attributes or drying performance alone. The effect of the foaming and stabilizing agents ratio at various temperatures on the physicochemical properties of the resulting powder will be studied and evaluated. The results showed that the formulation of foaming agent (egg white powder, EWP) and foam stabilizers (maltodextrin, MD, and carboxymethyl cellulose, CMC) affected the physicochemical properties of BPF extract powder prepared by the FMD. Among all the foaming agent formulations, the compositions EWP:MD:CMC of 16:20:1 and 8:10:1, with a drying temperature of 70 °C, showed the fastest drying time and produced extract powder with high anthocyanin content and solubility, as well as increased color intensity. Principal component analysis (PCA) supported the results, showing that the formula (8:10:1) has the highest evaluation score for physicochemical properties.