Whipped foams from Pickering O/W/O emulsion gel-based fat analogue: Thermal reversibility, oral tribology, and 3D printing characteristics dominated by fat crystals

Herein, a novel edible foam based on surfactant-free, gelled Pickering oil-in-water-in-oil (O/W/O) emulsion was developed using fat crystals as stabilizers of water-in-oil and air-in-oil interfaces while protein microgel as the stabilizer of oil-in-water interface, in which multi-chambered droplets and bubbles co-existed. The effects of fat crystals and fat amount, including palm oil (PO), anhydrous milk fat (AMF), and palm stearin (PS), on foam performance were evaluated. AMF-based foams exhibited a better aeration performance and a smoother cream-like sensation than PO, better interfacial stabilization on emulsion and foam were achievable by AMF crystals for greater diffusivity and a homogeneous spatial distribution, thereby allowing engaging in more interactions to support networks. Excessive PS was not conducive to the foam structure and led to a rough oral perception because more aggregated stiff PS crystals tended to destroy the water droplets. The introduction of gas greatly improved the rheological behaviors of O/W/O emulsions, and the viscous dissipation behavior for concentrated-droplets dominated foams was more pronounced at large deformation compared to bubble-filled foams. The microstructure and rheological behaviors further influenced the 3D printing properties of foamy systems as nutraceutical co-loading carriers for epigallocatechin gallate (EGCG) and lycopene. The tuneability of foam inks was permitted to improve printing accuracy, enhance the tolerance of printed objects to extrusion process through modulating the fat phase, thereby reducing the loss of EGCG and lycopene. This work is expected to provide a versatile soft foamy material with explicit and implicit multi-functionalities that finds interesting application in fat products.