Study of isothermic absorption model of moisture content of fibrous instant corn rice

Abstract

In general, storage of food products made from grains is carried out in an environment with uncontrolled air temperature and humidity. In this situation, changes in temperature and humidity will continue according to daily weather patterns. Food products stored in this environment will experience adsorption and desorption processes alternately and continuously throughout the day. Dried food that has not reached its equilibrium moisture content tends to absorb moisture during storage so that it will trigger a decrease in quality through a series of physical, chemical, and microbiological processes. The relationship between water activity and equilibrium moisture content during storage can be approached with an isothermic sorption model. The purpose of this research is to determine the equilibrium moisture content of fibrous instant corn rice in various relative humidity (RH) values and to find a mathematical model from isothermic sorption curve of fibrous instant corn rice. The research methodologies include the production of fibrous instant corn rice, the determination of equilibrium moisture content at various RH (40%-90%), and mathematical modeling of isothermic sorption curves with standard model approaches (Caurie, Hasley, and Oswin). The results showed that the water vapor adsorption process occurred in the isothermic sorption experiments of fibrous instant corn rice at a temperature of 30°C which was marked by an increase in the moisture content of the instant fibrous instant corn rice at 40-90% RH. Hasley equation model: (log [ln (1/aw)] = -3.2810 - 3.0945 log Me), Caurrie: (ln Me = -3.3084 + 1.8163 aw) and Oswin: (ln Me = -2.3301 + 0.2805 ln [aw/(1-aw)]) can accurately describe the isothermic adsorption of fibrous instant corn rice at 30°C because it has an Mean Relative Determination (MRD) value of less than 5.