Abstract
Chitin nanofibrils (NCh, ∼10 nm lateral size) were produced under conditions that were less severe compared to those for other biomass-derived nanomaterials and used to formulate high internal phase Pickering emulsions (HIPPEs). Pre-emulsification followed by continuous oil feeding facilitated a “scaffold” with high elasticity, which arrested droplet mobility and coarsening, achieving edible oil-in-water emulsions with internal phase volume fraction as high as 88%. The high stabilization ability of rodlike NCh originated from the restricted coarsening, droplet breakage and coalescence upon emulsion formation. This was the result of (a) irreversible adsorption at the interface (wettability measurements by the captive bubble method) and (b) structuring in highly interconnected fibrillar networks in the continuous phase (rheology, cryo-SEM, and fluorescent microscopies). Because the surface energy of NCh can be tailored by pH (protonation of surface amino groups), emulsion formation was found to be pH-dependent. Emulsions produced at pH from 3 to 5 were most stable (at least for 3 weeks). Although at a higher pH NCh was dispersible and the three-phase contact angle indicated better interfacial wettability to the oil phase, the lower interdroplet repulsion caused coarsening at high oil loading. We further show the existence of a trade-off between NCh axial aspect and minimum NCh concentration to stabilize 88% oil-in-water HIPPEs: only 0.038 wt % (based on emulsion mass) NCh of high axial aspect was required compared to 0.064 wt % for the shorter one. The as-produced HIPPEs were easily textured by taking advantage of their elastic behavior and resilience to compositional changes. Hence, chitin-based HIPPEs were demonstrated as emulgel inks suitable for 3D printing (millimeter definition) via direct ink writing, e.g., for edible functional foods and ultralight solid foams displaying highly interconnected pores and for potential cell culturing applications.
Highlights
High internal phase emulsions (HIPEs) generally refer to those containing a volume fraction of the dispersed phase φ > 74%.1 They display a large surface area per volume of the continuous phase,[2] which affects uniquely their flow behavior.[3]
Stable oil-in-water, high-internal-phase Pickering emulsions stabilized by chitin nanofibrils were successfully prepared using a simple two-step strategy
Two possible underlying mechanisms for the formation and stabilization of high internal phase Pickering emulsions (HIPPEs) are proposed: (1) structuring continuous phase to form deformable, connected, fibrous network structures upon Pickering pre-emulsification, with oil droplets covered with NCh, which prevents the droplets from approaching each other and arrests coarsening, and (2) irreversible adsorption of NCh at oil/water interfaces, inhibiting coalescence and breakage of oil droplets
Summary
High internal phase emulsions (HIPEs) generally refer to those containing a volume fraction of the dispersed phase φ > 74%.1 They display a large surface area per volume of the continuous phase,[2] which affects uniquely their flow behavior.[3]. The emulsions with >74% oil fraction were not stable, suggesting that relatively low NCh loading is insufficient to generate Pickering pre-emulsion droplets, for example, by interfacial adsorption, and to enable sufficient structuring during preemulsification This result highlights that the initial network structure plays a key role in stabilizing HIPPEs. As an extension of previous discussion, NCh of longer axial aspect (produced via microfluidization46) was applied at 0.3 wt % in the aqueous phase (Figure S7). NCh-stabilized HIPPEs are demonstrated as a route to fabricate porous materials with great potential for the construction of supports and scaffolds with possible uses in bioengineering, food and pharma, catalysis, among others
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
