Theoretical kinetics of baking


A potato is composed of 80% water and 20% solids. Of the solids, 99.5% is starch. Some of the starch is amorphous and some of it is crystalline. When a potato is subjected to heat, the crystalline starch gelatinizes into amorphous starch by the reaction below.


The integrated kinetics equation of this starch gelatinization[8] at constant temperature is:


where x = mass of starch that gelatinized during time t divided by the total mass of starch that can gelatanize.

When a potato is being cooked, the temperature at any point in the potato changes with time; therefore the reaction constant, k, will change with time because it is a function of temperature as given below:

Because of this variance, we have to use the differential form (shown below)of the kinetics equation which we found by differentiating the integrated form.

The center of the potato is the last part to get cooked, so when it’s cooked, we know that the rest of the potato is also cooked. A cooked potato is defined when x=0.779. Therefore, the initial conditions are x = 0 when t = 0 and the cooking time can be found when x=0.779.