Mathematical models for the drying process of king-palm shells biomass colonized by shiitake mycelium

Abstract

To obtain the heart-of-palm in the king-palm (Archontophoenix cunninghamiana) processing there are solid wastes generation such as the shells, which causes environmental damage if inadequately disposed of. These shells are nutritiously attractive to feed and when they are colonized by edible basidiomycete fungi it could result in the value addition through the generation of products for human consumption. This study proposed the mathematical-modeling fitting to the experimental values in function of temperature on the drying time of a biomass containing the king-palm shells colonized by the fungus Lentinula edodes mycelia, also known as Shiitake mushroom. The substrate colonization process was conducted in a solid-state fermentation system (SSF) at 25 °C for 40 days. The resulting biomass was utilized for the drying kinetics study in a convective oven, constructing the drying curves for the 35, 50, and 65 °C temperatures, and subsequent fitting of empirical and semi-empirical mathematical models to the experimental data of the drying process. The equilibrium moisture and the drying times resulted, respectively, 205 minutes and 0.22% to 35 °C, 145 minutes and 0.28% to 50 °C, and 115 minutes and 0.12% to 65 °C. Ten mathematical models were tested and all of them presented adjustments to the experimental curves, however, the ones that represented more satisfactorily the moisture loss during the drying time were the Modified Midilli-Kucuk model, the Two-term model, and the Logarithmic model (R²=0,998) to 65 °C (temperature selected as the best for the studied process). At the end of the study, the dried biomass was ground and generates a flour, which the analysis indicated similar nutritional values, independently of the drying temperature. Therefore, the transformation of heart-of-palm shells under the proposed conditions brings that it could obtain a future diet product besides that the sustainable practices applied to the production chain of the king-palm could result in the decreasing an environmental passive.