Foaming properties, microstructure, and mathematical model of foam mat drying of pasta sauce based on tomato

In the present study, the foam mat drying technique was used to dry pasta sauce based on tomato to become powder. The effect of different egg white concentrations (3, 6, and 9%) and whipping time (2 min and 5 min) on the foam properties of pasta sauce, including foam density, foam expansion, foam viscosity, water activity, morphological and drying behaviour, were investigated. The foamed sauce was dried in a batch-type thin-layer dryer at constant conditions (temperature of 60 °C). Six thin-layer drying models were employed to determine the drying kinetics of the pasta sauce. The results showed that an increase in the egg white concentration and a decrease in the whipping time produced a foamed sauce with low foam density and viscosity and high foam expansion. The Wang and Singh model was the best model to describe the drying behaviour of foamed sauce. According to Fick's second law model, the effective moisture diffusivity of the pasta sauce ranged from 4.95 × 10–7 to 10.04 × 10–7 m2 s–1.