Green extraction method and microencapsulation of tannins from young coconut husks-based food waste using gelatin/nanofiber cellulose

Young coconut husk, a by-product of food waste, is generated in significant quantities, yet the potential of its bioactive compounds has not been fully explored. This study aims to extract tannins from young coconut husks using an eco-friendly method, optimizing temperature and the gelatin/cellulose nanofiber (NFC) ratio as encapsulants to achieve optimal microcapsule characteristics. The research was conducted in three stages: eco-friendly tannin extraction, optimization of the tannin encapsulation process using response surface methodology (RSM), and characterization of the microcapsules. Tannin characterization assessed tannin content and yield, while microcapsule examined tannin content, yield, water content, solubility, stability, surface morphology, functional groups, total phenolic, IC50, and antimicrobial activity. The eco-friendly extraction of coconut husk produced tannin content and yielded 14.97 % and 16.35 %, respectively. The optimal conditions for tannin microencapsulation were found at 60.64 °C and a gelatin/NFC ratio of 0.69, which achieved maximum tannin content, solubility, and yield while minimizing water content. Tannin microcapsules are more stable at lower pH and temperature. Additionally, thin-layer drying produced microcapsules with higher tannin content, yield, and moisture content than spray drying. The surface morphology of microcapsules dried in thin layers appeared relatively rough and exhibited non-uniform size compared to those dried with a spray dryer. Analysis of functional groups indicated interactions between the functional groups of tannins and those of gelatin and NFC. Tannin microcapsules demonstrated high total phenolic values, IC50, and antimicrobial activity, suggesting their potential application in broader fields, including the pharmaceutical and food industries, as sources of bioactive compounds.