Comparison and modeling of moisture sorption isotherms of deproteinized rapeseed meal and model extrudate

Abstract

The equilibrium moisture contents (EMC) of deproteinized rapeseed meal (DRM) and model extrudate, prepared from DRM and corn grits (1:1), were determined at different temperatures (20°C, 30°C, and 40°C) and water activities (0.112 to 0.851) using the static gravimetric method. The model extrudate exhibited lower sorption capacity and significantly greater hysteresis loop than these of the DRM. Five models including the effect of the temperature were applied to analyze the experimental data. The modified models of Oswin and GAB were found suitable for describing the relationship between the equilibrium moisture content, the water activity, and the temperature. In the range of temperatures studied, the DRM and the extrudate were characterized by monolayer moisture at water activities of 0.10 and 0.16, respectively. For long-term storage at 20°C, maintaining water activities from 0.10 to 0.60 and EMCs from 7.36% d.b to 17.09% d.b. for the DRM and water activities from 0.16 to 0.60 and EMCs from 6.43% d.b to 13.61% d.b. for the model extrudate were suggested. The study demonstrated the usability of the DRM for the production of a model extrudate suitable for long-term storage. Practical applications The European Union developed a concept for recycling waste and by-products from food and agricultural industries and their reuse in innovative food products. In this regard, characterization and investigation of the potential application of deproteinized rapeseed meal (DRM), appearing as a waste of protein isolation from industrial rapeseed meal, was initiated. The implementation of DRM in new extruded products with functional characteristics and long-term storage would be economically, socially, and environmentally significant. Knowledge of the sorption behavior of food products is essential for their microbiological and biochemical stability during storage. Data generated in this study could be valuable for designing technological and/or storage parameters that allow optimization of heat and mass transfer processes while working with these materials.