Hysteresis, what is this peculiar word?

Hysteresis is the difference between the gelling and melting temperatures of a gel.

Agar has the highest hysteresis of all hydrocolloids. Once dissolved at 1-1.5% concentration in water, the solution forms a gel upon cooling to 34-38 ° C, and that gel only melts if heated to 85-90 ° C, not before.

This interesting property allows solutions to solidify easily at room temperature, without the need for refrigeration, so that this gel can be heated again, keeping it stable until quite high temperatures. Curiously, this makes it possible to have an agar solution, in the range of 35-85ºC, either in the liquid state or in the gel state.

Being able to keep a solidified product hot makes its cooking use more flexible or keeps the structure stable at room temperature even in very hot spaces. It is very useful, for example, to work on toppings or icings. It also allows to make gel without refrigeration, unlike gelatin that needs temperatures below 15ºC to gel and therefore a refrigerator.