Thermodynamic properties of barley hydration process and its thermostability

Barley is a winter cereal grain used mainly in brewing malt production and is ranked among the top five cereal grains produced in the world. The objective of this study was to evaluate isothermal hydration at different temperatures (30, 35, 40 °C) and obtain the thermodynamic properties, as well as characterize the thermostability of the Scarlet cultivar and evaluate the starch gelatinization temperature. The micrography showed that hydration causes gradual peeling and swelling of the starch granules, compatible with a heterogeneous hydration of different anatomical structures. The moisture absorption rate increased with the temperature. The kinetics of the grain hydration was simulated using the models of Peleg and Omoto–Jorge. The Peleg model was more suitable for predicting the kinetics, and the data distribution revealed three distinct phases. Thermal degradation of barley revealed three peaks: loss of moisture, nonoxidative degradation, and oxidative degradation. Starch gelatinization occurred at 62 °C. Practical applications The evaluation of hydration kinetics demonstrates that an increase in temperature improves the rate of mass transfer in the grain. This practice can be applied in the industry to optimize the process. The micrograph confirms that changes occur in the barley during hydration. Mathematical models allow for verification of how better to predict the process so that it may be generalized to enable the simulation of industrial conditions. The thermodynamic parameters obtained by process modeling provide information concerning the affinity between water and the grain, the spontaneity of reaction, the degree of disorder, and the energy required for the process; this data is useful for modeling, design, and optimization of the industrial process. The thermostability evaluation provides relevant information for choosing temperatures that may be used in industrial practices, as well as for changes in physical state (i.e., whether or not gelatinization is favorable for the process).