Testing Equilibrium Moisture Effects
Food products may lose quality if the moisture level changes from the equilibrium moisture in the distribution chain. The rate of moisture change can be monitored by changes in package weight which occur during storage in appropriate temperature and humidity environments. Medallion Laboratories has computerized this old technique and applied it to wide variety of food products. For products that suffer quality losses in high humidities, the packages stored in what is known as the "weather room". This room is kept at constant 65% RH with temperature cycling on a day/night basis between 90 F and 74°F. These conditions are used to simulate the hot, humid summers of the southeastern United States The packages are weighed back at weekly intervals and the gain in weight, along with the original moisture determination, are then used to calculate the moisture changes. From the moisture sorption curve developed for the product and knowledge of the package material water vapor transmission rate (WVTR), a calculation can be made to determine its shelf life.