ABSTRACT
The objective of this research was to determine the experimental equilibrium moisture content curves (EMC) and latent heat of vaporization (LHV) for popcorn (Zea mays) seeds. The initial moisture content of the seeds was 23% (wetted basis). The seeds were submitted to dessorption under different temperatures (20, 30, 40 and 50ºC) and air relative humidities (30, 40, 50, 60, 70, 80 and 90%) with three replications, until reaching the moisture equilibrium. An "Aminco-Air" air conditioning unit controlled the temperature and relative humidity of the air. The following mathematical models were fitted to the experimental data: Henderson, modified Henderson, Chung-Pfost, Copace and Sigma-Copace. The constants for these equations were obtained by regression, while the latent heat of vaporization was calculated using the modified Henderson equation, fitting an empirical equation to estimate the latent heat of vaporization for the popcorn as a function of temperature and moisture content. According to the results obtained, it was concluded that the Copace and Sigma-Copace equations were the ones that best fitted to the experimental data, for all studied ranges of temperature and relative humidity of the air, and might be used to calculate the equilibrium moisture content for popcorn seeds. The fitted empirical equation for calculating the LHV of popcorn seeds proved to be adequate.
Key words:
popcorn; equilibrium moisture content; latent heat of vaporization