Hysteresis phenomenon in foods

It has been explained that hysteresis is a sorption phenomenon, which rests on temperature, Aw, moisture content and on surface energy Q. As temperature and Aw as environmental variables have opposite effects on moisture content the isobar and isotherm methods are bound to have opposite effects on the hysteresis loop. Using Caurie's equation it has been shown that the desorption isotherm of the hysteresis loop is always at a higher energy level than the adsorption isotherm. This energy difference is stated to arise from physical changes in the adsorbent matrix which expose new energetic sites which adsorb moisture on return to lower Aws rather than desorb moisture and this is indicated to be responsible for the hysteresis phenomenon. It has also been argued that hysteresis may be used as an index of food quality.