3.2 Hygrometric method

Electric hygrometers are widely used for obtaining the MSIs of agricultural and food products. There are quite a lot of commercially available and specially designed hygrometers that are in use. The instrument (Figure 4) consists basically of a sensor, sample chamber and potentiometer. The sensor could use a hygroscopic chemical such as lithium chloride or an ion-exchange resin such as sulfonated polysterne; the conductivity of which changes according to the water activity above the sample. The sensor could be a humidity sensor which is based on capacitance changes in a thin film capacitor. Electric hygrometers give rapid, relatively precise results and are easy to operate. The main problems involved with the use of hygrometers are:


Crapiste and Rostein [57], Fasina and Sokhansanj [58], Tsami et al. [17] and Arslan and Togrul [59] employed the hygrometric method in studying the moisture sorption behavior of potatoes, alfalfa pellets, model fruit powders and crushed chillies, respectively.

Figure 4. Diagram of moisture sorption isotherm apparatus utilizing the hygrometer. Source: Fasina and Sokhansanj [58].

Moisture Sorption Isotherms and Isotherm Model Performance Evaluation for Food… DOI: http://dx.doi.org/10.5772/intechopen.87996
