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.