Water-in-oil-in-water emulgels with internal aqueous phase gelation for controlled soymilk coagulation

This study evaluated the effects of internal aqueous phase gelation on water-in-oil-in-water (W/O/W) emulgel stability and their potential for controlled soymilk coagulation to produce soft tofu. Incorporating gelatin or κ-carrageenan gelled the internal aqueous phase, leading to a decrease in droplet size. For κ-carrageenan, this incorporation also resulted in a ζ-potential more negative than –30 mV. All emulgels displayed elastic characteristics, showing higher G' values compared to G''. Emulgels containing over 2.5% κ-carrageenan showed the highest G' values and apparent viscosity, consistent with enhanced thermal, storage and centrifugal stability. The incorporation of gelatin suppressed creaming and droplet size increase in the emulgels during storage and freeze-thawing. The encapsulation efficiency (EE) of MgCl 2 was increased to over 88%, and its release rate was significantly slowed. The yield and hardness of tofu coagulated with emulgels were, respectively, 32%–74% higher and 36%–66% lower than those of tofu coagulated with MgCl 2 solution. This was in accordance with the increased water content, which is semi-bonded water within the gel network. Microstructure analysis indicated that the controlled coagulation resulted in a homogeneous protein network with uniformly distributed micropores. The increased proportion of β-sheet structure implies more extensive interactions between amino acid residues, contributing to a more ordered conformation. The delayed coagulation time and the lower G′ values of soymilk coagulated with emulgels further confirmed the controlled coagulation. These findings indicated that internal aqueous phase gelation enhances emulgel stability and controls soymilk coagulation, demonstrating their potential as coagulants for producing soft tofu with high yield.