Mathematical modeling of the spray drying processes at laboratory and pilot scales for the development of functional microparticles loaded with chia oil

Abstract

Spray drying is a well-known operation to formulate food powders. Usually, the dryer performance is evaluated through trial and error given the complexity of transport phenomena. Regarding the microencapsulation of functional chia oil by spray drying, the main contribution of this study was to compare the accuracy of fundamental models for predicting the values of process variables (drying-air outlet temperature, Toutlet and feed flow rate, Vfeed) and powder properties (size, d32 and moisture content, H), under a wide range of drying conditions at laboratory (Büchi B-290) and pilot scales (Niro Production Minor). First, the coarse-scale approach modeled the dryer´s chamber as a well-mixed reactor. The experimental values for Toutlet were: 72–109 °C (laboratory scale) and 75, 90 °C (pilot scale); moreover, the experimental Vfeed values were in the following ranges: 2.8 and 5.6 mL.min−1 (laboratory scale) and 59–197 mL.min−1 (pilot scale). With the coarse-scale approach, absolute average deviations (AAD) below 7% between experimental and calculated values were observed for Toutlet and Vfeed. However, large prediction errors (>10%) were observed for H, for which the experimental values were in the range of 2.4–4.5% for both scales. On the contrary, the finer-scale approach consisted of a plug-flow model, with incorporated drying kinetics and spray droplet sizes. This model could accurately predict Toutlet, H and d32, with AAD values below 10%. Both simulation and experiments are useful tools not only for spray drying optimization, but also for improving the oxidative stability of microencapsulated oils by target-oriented design.