Acta Scientiarum Polonorum Technologia Alimentaria

Background. Asparagus root (Asparagus officinalis L.) is one of the herbaceous by-products with potential for making added-valued food products, due to its excellent nutritional properties and flavor/fragrance. In order to maintain its quality, several drying methods were investigated to select an advanced one that could be widely applied in the processing of dried vegetable products.
Materials and methods. A thin layer at 40–90°C using a thin-layer drying oven was investigated to study the thermal degradation kinetic of bioactive compounds, including vitamin C, phenolic, flavonoid, saponin and antioxidant capacity of dried asparagus roots. Linear and non-linear regression analysis (zero-, first and second-order) was employed to assess the parameters, which helped select the optimal model that accurately characterizes an efficient drying process for asparagus roots.
Results. The first-order model was described for vitamin C degradation and matched the experimental data well. The decomposition of phenolic, flavonoid, saponin and antioxidant capacity followed the second-order model with the highest coefficient of determination value (R2 > 0.99) and the lowest root mean squared error (RMSE) value. Enhanced levels of bioactive compounds and antioxidant capacity notably slowed down the degradation of anthocyanins at a temperature of 70℃.
Conclusion. This study reflected the thermal degradation kinetic for the drying process. The results could provide useful information for the optimizing the drying of asparagus roots with the aim being to obtain a product with high nutritive quality and bioactivity.