Cellulose stabilized palm oil emulsions as 3D printing inks: Controlled release of d-limonene

Natural essential oils, such as d-limonene, are frequently used as flavoring agents and fragrances in the food industry. However, their susceptibility to volatilization and chemical degradation poses challenges for widespread application. In this study, cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) were used to stabilize palm oils (POs) with different melting points to prepare Pickering emulsions (PEs) for the encapsulation of d-limonene. The physicochemical properties, environmental stability, 3D printing performance, and retention of d-limonene were explored. It results indicated that CNFs stabilized PO emulsions exhibit a stronger gel network structure, particularly pronounced in high melting point PO. CNF-stabilized emulsions enhanced stability to pH changes, salt ion, and storage conditions, due to a greater gel structure. Notably, it should be noted that CNCs and CNFs slowed down the release of d-limonene in both fresh and heat-treated emulsions. Furthermore, CNCs and CNFs emulsions as 3D printing inks, ensure accurate and stable formation of target shapes. The volatilization of d-limonene during the process was effectively suppressed (<9 %). The lower release of d-limonene in CNF emulsions (<2.8 %) could be linked to the tight distribution of CNF particles between the oil/water interface and the droplets, which makes the emulsion more resistant to extrusion. This study provides valuable insights into the use of PEs for encapsulating flavor components in 3D printing applications.