Acta Scientiarum Polonorum Technologia Alimentaria

Background. Asparagus root (Asparagus officinalis L.) is one of the herbaceous by-products with potential for making value-added products because of its excellent nutritional properties and flavor/fragrance. In order to maintain its quality, drying is suggested as a suitable technique for this purpose. Several drying methods were set up to investigate and select the one which had a high reliability of drying parameters and could be widely applied in the processing of dried vegetable products.
Materials and methods. Thin-layer drying at six temperature degrees (40°C, 50°C, 60°C, 70°C, 80°C, and 90°C), solar system, and sun drying were investigated to study the kinetics of moisture ratio change in asparagus roots. Eight common drying kinetic models (Haghi and Angiz II, Henderson Pabis, Logarithmic, Newton, Page, Parobolic, Peleg, and Wang and Singh) were applied to choose the most fitting. The moisture diffusion efficiency and activation energy were determined by Fick’s diffusion equation.
Results. Rising drying temperature accelerated the drying speed, and the Page model was indicated as the best fit for the experimental data among the remaining drying models. The moisture diffusivity values varied from 9.11 × 10–12 to 1.27 × 10–11 m2/s for the thin-layer drying method and 1.2 × 10–11 and 9.55 × 10–11 m2/s for the solar system and sun drying models, respectively. The efficiency of moisture diffusivity depended on investigating drying models, which was described using the Arrhenius’s equation with an activation energy of 30.91 kJ/mol.
Conclusion. The page model is the most suitable for describing the drying process of asparagus, with high reliability between the experimental data and estimated data from this model when drying asparagus at 70°C (R2 = 0.9996).