Drying curve modelling of blanched carrot cubes under natural convection condition

Abstract

Carrot cubes were submitted to combined treatments of blanching and drying. Blanching was alternatively performed 3 min in boiling 5% brine solution, 3 min in boiling water or 6 min in boiling water. It was observed that the applied pre-treatments influence on the kinetics of drying. The mathematical model describing the course of drying curve of single blanched carrot cubes (not touching each other) under natural convection condition was formulated on the basis of the general theory of heat and mass transfer laws. The course of the drying curve was described in two ways: (i) using the linear model of the first drying period (without shrinkage) and then using the model of second drying period; and (ii) applying the model of first drying period taking into account shrinkage and followed by the model of second drying period. The second drying period was described in both cases by the same model which approximated the shape of dried particle to the cube. It turns out from the verification that the values of relative error (RE) were not higher than: 1% for linear model, 20% for model with shrinkage, 40% for model of cube drying. The correlation between the data obtained from mathematical models and empirical data was high (the lowest correlation coefficient amounted to 0.96). Proposed mathematical model can be accepted. The results obtained from the experiments and from mathematical modelling suggest that drying of carrot cubes occurs in the first and the second drying period.