Effect of Temperature and Relative Humidity on Yellowing Rate of Paddy

Abstract

The effects of temperature and relative humidity in storage chambers on yellowing rate of paddy were investigated and then an empirical equation for predicting the yellowing rate was developed. Paddy was conditioned using saturated salt solutions at relative humidities from 80 to 95 % and temperatures 35, 45, 55, 60, and 65°C. The yellowing rate was found to follow the zero order kinetics. The yellowing constant values (k) increased exponentially with temperature while increased linearly with water activity. The magnitude of activation energy varied from 130-145 kJ/mol. A predictive equation for determining yellowing rate was ln k = α - δa_w - ε/T + ()/T where a_w is water activity (valid from 0.80 to 0.95), T is absolute temperature (valid from 308 to 338 K) and α, δ, ε and are constants. The results of variance analysis showed that temperature, water activity and their interaction significantly influenced the yellowing rate of paddy.