Yifu Chu | ALES Graduate Seminar

Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree. This is an ALES PhD Final Exam Seminar by Yifu Chu. This seminar is open to the general public to attend.

PhD with Drs. Lingyun Chen and Wendy Wismer       

Thesis Topic: Development of Protein Microgels Using a Novel Water-in-Water Emulsion Method and Their Functional Applications

Abstract:

Microgels have garnered increasing attention as versatile building blocks and functional ingredients for applications in food science, biomaterials, and beyond. This PhD research aims to address the current challenges in developing uniform, size-controllable protein microgels and exploring their performance in bulk and interfacial systems to create innovative solutions for healthier food products and functional biomaterials. In the first study, a facile water-in-water (W/W) emulsion method was innovated to prepare whey protein microgels based on protein-polysaccharide segregative phase separation. This approach enables precise control over microgel sizes (1–20 μm) with uniform distribution and offers two significant advantages over traditional microgel fabrication methods: 1) The W/W droplets can remain stable without adding surfactants, enhancing biocompatibility for food and biomedical applications; 2) the process requires low energy input due to the ultra-low interfacial tension of W/W droplets, improving commercialization potential.

Oil-in-water emulsion stabilized by these microgels demonstrated exceptional stability and textural properties, prompting our further investigation into the underlying emulsification mechanisms of this system. The second study demonstrated two key stabilization mechanisms: 1) microgels adsorbing at the oil/water interface to stabilize Pickering emulsions and 2) microgels dispersing in the continuous phase to act as fillers to enhance emulsion texture. Varying microgel content effectively tailored the rheological properties in both scenarios. Proteins contribute fewer calories than fat, thus showing strong potential as fat replacers for developing novel low-calorie foods with enhanced texture and reduced fat content.

The third study shed light on the lubrication performance and underlying mechanism of these protein microgels, which is essential for predicting the fat-mimic mouthfeels, such as creaminess. It was observed that the microgel suspension showed several folds of reduction in coefficient of friction in comparison to native protein and human saliva via tribological measurements. The exceptional lubricity was from a synergistic effect of the ball-bearing mechanism and the hydration state of the microgels.

Granular hydrogels are a promising class of 3D-printable inks but often suffer from low printing resolution due to large microgel sizes (>100 μm). In the last study, we developed a novel class of granular hydrogels (WMGH) composed of uniform, size-controllable whey protein microgels. The small microgel size enabled WMGH ink to achieve high 3D printing resolution to produce intricate constructs such as aortic valve structures with high fidelity. By incorporating a polyacrylamide second percolating network, WMGH inks were transformed into stretchable, tough double-network granular hydrogels (DN-WMGH). Controlling microgel size offered a new approach to tailor mechanical strength (6–300 kPa), idea for tissue-mimicking applications.

This work developed a novel, facile method to produce protein microgels via protein-polysaccharide segregative phase separation, demonstrating strong industrial potential. This research signified the value of these uniform, size-controllable protein-based microgels as functional ingredients for developing healthier food products and functional biomaterials. Notably, this research supports the development of fat-reduced foods with enhanced mouthfeel comparable to full-fat counterparts, providing healthier dietary options to control the obesity crisis. Additionally, it expands the potential of these microgels for biomaterial applications, including tissue-mimicking implants and 3D bioprinting for tissue regeneration, contributing to healthier outcomes.