syneresis

Syneresis is the expulsion of liquid from a gel, colloid, or emulsion as the network contracts or reorganizes. The term describes a process in which a gel loses its solvent, causing droplets or a separate liquid phase to form and separate from the solid phase. It is observed in various systems, including food gels, dairy products, and some clayey soils.

The underlying mechanism involves changes that weaken or compress the gel network or create osmotic/ capillary forces that drive solvent out of the network. Temperature shifts, pH changes, ionic strength, enzymatic action, or drying can promote syneresis. In gels with loosely cross-linked or weak networks, the tendency to shrink and squeeze out liquid is higher.

Common contexts include dairy products and foods. In yogurt and custards, whey separation is a familiar manifestation of syneresis, often increasing with storage time or heating and can be influenced by pH near the isoelectric point of milk proteins. Gelatin desserts and starch-based gels may also exhibit liquid separation under certain storage or usage conditions. Syneresis is also described in soils and clays, where drying causes the gel-like pore water to be expelled, potentially leading to cracking known as syneresis cracks.

Prevention and control focus on strengthening the gel network and stabilizing conditions. This may involve adjusting pH and salt concentrations, adding stabilizers or gelling agents (such as gums or carrageenan), controlling temperature to avoid rapid shrinkage, and maintaining moisture. Understanding syneresis is important in food quality, gel science, and soil physics.