Smart pH Indicators for Sustainable Applications: Mechanistic Insights into Reusable and Leak-Resistant Anthocyanin-Loaded Cellulose Acetate Beads

The usage of intelligent indicators in predicting and communicating dynamic shelf life of foods to consumers is unrivalled. Clitoria ternatea anthocyanins can change color upon exposure to different pH conditions but are unstable when applied directly or in film form. To address this issue, we have encapsulated anthocyanins extracted from C. ternatea in cellulose acetate (CA) and formed beads via precipitation and the phase inversion method. The total anthocyanin content and encapsulation efficiency were calculated as 6.95 mg Cyanidin-3-glucoside equivalent/g of dry flowers and 99.50%, respectively. Later, effects of C. ternatea-loaded CA beads on physical, structural, thermal, and pH-sensitive properties were analyzed. An attempt was made to represent the mechanism of bead formation in gelling bath with the help of the Marangoni effect of hydrodynamic instability. Attenuated total reflectance infrared spectroscopy revealed that there are no inter-/intramolecular interaction upon loading of anthocyanins to CA beads. ACN-CA beads are pH-sensitive; when exposed to pH 3 and 4, beads have shown violet to blue color, and at pH 11 and 12, yellow shade was visible. The beads do not release anthocyanins into water medium owing to the asymmetric structure formed during precipitation and osmotic pressure differences. Our results suggest that the developed beads can efficiently replace the existing pH- sensitive intelligent packaging indicators in food sector and offer excellent reusability.