In the kitchen, oftentimes we desire to thicken a sauce or a broth without significantly changing its flavor. There are several ways to do this, and the physicochemical principles behind them are quite different in many cases. One way of thickening things is just to reduce them (i.e., boil them down), but that often involves chemical changes that alter flavor.
Other ways of thickening things including adding small amounts of rather bland ingredients that cause the sauce or other material to become thicker without extreme heating, or to create a complex emulsion that thickens materials due to physical rather than chemical changes. We shall examine some of both this evening.