Imagine we have a special oil-water mixture that has more than 74% oil in it, called high internal phase emulsions (or HIPEs for short), a gel-like mixture that can be used as a replacement for high oil products such as partially hydrogenated oils or mayonnaise due to its uniqueness, or even as edible 3D printing inks.

In October 2023, Professor Chen Xianggui's group at the School of Food and Engineering, Xihua University published a paper entitled “High internal phase emulsions stabilized by walnut protein amyloid- likeaggregates and their application in Food Hydrocolloids” in Food Hydrocolloids. likeaggregates and their application in food 3D printing” (IF=10.7), in which the rheological properties of high internal phase emulsions (HIPEs) stabilized by walnut protein isolate (WPI) and their amyloid-like aggregates (WPIA) were investigated and tested. printing performance of WPIA-stabilized HIPEs as edible food inks for 3D printing, providing an important experimental perspective on the influence of protein-like amyloid fibril aggregates on the rheological properties of stabilized HIPEs.

The research team first prepared walnut amyloid protein-like aggregates (WPIA) by a special method and used two different dyes to label the proteins and oil droplets, observed the morphology and microstructure of the oil droplets in the HIPEs with the help of a SOPTOP CLSM600 laser confocal scanning microscope, and found that the concentration of the emulsifier and the acid-base value (pH) have a stability of the high internal phase emulsions (HIPEs) have a great influence.

Under acidic environment (pH 3.0), walnut isolate protein was effective in stabilizing the high internal phase emulsions, forming Pickering-type HIPEs with solid particles as emulsifiers.In contrast, the HIPEs stabilized by walnut isolate protein had better energy storage capacity and lower yield stress.

At neutral pH 7.0, although the stabilizing effect of walnut isolate protein was weakened, walnut protein amyloid aggregates (WPIA) could still maintain the emulsion structure to a certain extent, whereas walnut isolate protein alone barely stabilized the HIPEs in a neutral environment due to its poor solubility.

CLSM600 microscopy images of HIPEs stabilized by WPI and WPIA at pH 3.0 and HIPEs stabilized by WPIA at pH 7.0

Compared with ordinary inverted fluorescence microscopy, confocal microscopy can provide higher resolution and image clarity, reduce the interference of background signals and improve the contrast of images.

Meanwhile, the laser light source has higher brightness and penetration, which is more advantageous for observing samples with complex structures or more opaque samples such as HIPEs.