Abstract Does the chemical principle of tofu production using magnesium chloride as a coagulant belong to “protein salting-out” or “colloidal coagulation”? To clarify this conceptual confusion, this article systematically analyzes the essential differences between the two based on colloidal and protein chemistry theories, combined with experimental evidence. Soybean milk is a typical colloidal system; from four core dimensions: mechanism of action, reversibility of the process, dependence on electrolyte concentration and valence, and product structure, it is demonstrated that the essence of tofu production using MgCl2 as a coagulant is colloidal coagulation: Mg2+ compresses the double layer of soy protein colloidal particles in soybean milk, reducing the ζ potential of the colloidal particles to below 20 mV, triggering irreversible aggregation of the colloidal particles and forming a three-dimensional gel network, rather than protein salting-out.
FAN Zong-Shan, LI Zhou-Ping. Chemical Principle Behind Making Tofu with MgCl2 as Coagulant: Colloidal Coagulation Rather than Protein Salting-Out[J]. Chinese Journal of Chemical Education, 2026, 47(1): 125-129.
