Question

Explain how sauces thicken during heating/cooling as it relates to the starch molecules.

Answer 1

Gelatinization of starch involves breaking down the bonds in starch molecules under the influence of heat when mixed with water. The process of gelatinization is very common and the concept is used in various fields. Similarly, when any form of starch is added to sauces it absorbs water when heated at around 60-70^oC(this varies). The starch heats up more in the liquid absorbing enough liquid to their capacity and the molecules begin to breakdown. This heating of starch breaks the granules as the molecules are in motion. This causes the eventual thickening of the liquid as starch gets completely released and soaked up in the liquid. At near boiling or high temperatures gelatinization complete which is irreversible. When this is cooled to below 40^oC it thickens even more.

Therefore it involves three steps-

physical absorption of water by starch molecules,

water molecules enter into the starch molecule

disruption of starch granules and release of small starch molecules into the liquid