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Sufu is a delicious traditional Chinese food, mainly produced by fermentation using soybeans as raw material. Egg white is rich in protein and is theoretically an excellent material for sufu processing, however there are few reports on egg-white sufu (EWS) currently, and no such product is available on the market. In this paper, a novel sufu was processed with egg white as main material, and the formation mechanism of its unique quality was explored by monitoring the dynamic changes in the pre-fermentation and post-fermentation stages. The dynamic change curve of protease activity showed an “S” shape, with a peak of 32.33 U/mL on the 4th day of pre-fermentation stage. After a 4-day pre-fermentation and 90-day post-fermentation, most of the proteins in the EWS had been hydrolyzed, and the sufu was moderately soft and delicate in texture, with a hardness of 950.3 g and a total free amino acid content of 19.863 mg/g. SEM and SDS-PAGE detections suggested that the proteins in EWS had been extensively degraded, which led to the formation of its unique texture and flavor. The EWS was slightly better than soybean sufu in terms of texture, fragrance and mouthfeel, with flavor compounds mainly composed of aldehydes and alcohols, resulting in a slightly higher total sensory evaluation score.

In this paper, we interpreted the “twice gelation” mechanism of egg-based yoghurt through the integrated multidimensional dynamic change analysis of rheology, microstructure, and intermolecular forces. The results showed that during the first gelation stage (i.e., thermal gelation), egg proteins underwent heat denaturation and formed crosslinks, with the main intermolecular forces involved in gel formation being disulfide bonds (∼84%). After homogenization by the colloid mill, the heat-induced gel transformed into a smooth, viscous fluid state, which subsequently turned into a weak gel as the pH continuously decreased under the effect of lactic acid bacteria fermentation. In the second gelation stage (i.e., acid gelation), the proportion of hydrophobic interactions increased from ∼12% to ∼49%, whereas the proportion of disulfide bonds decreased from ∼74% to ∼45%, indicating that hydrophobic interactions played a crucial role in the second gelation, while disulfide bonds still showed great importance in stabilizing the gel structure, although their percentage decreased significantly. In summary, egg proteins form a hard gel by heating, and this heat-induced gel has the ability to gel twice after homogenization, making it possible to form egg-based yoghurt with a fine texture and good taste under the action of lactic acid bacteria fermentation.