Pasteurização de polpa de manga usando coordenadas generalizadas tridimensionais.

Abstract

Pathogenic microorganisms are causes of many foodborne illnesses. The strict control of foods need to a necessary sound knowledge about peculiar thermophysical properties to each product. This work purpose to study the physical phenomenon of transient heat diffusion, assuming contour condition of the first type in pulp of mango (Tommy Atkins varieties), contained in a container with elliptical geometry. Thus, this research has an objective to analyze and make available the implications of considering diffusivity as a function of the local temperature inside the product, which allows for greater accuracy in describing heat transfer. Based on this, a 0,7 mm thick stainless steel container was made and used in which two thermocouples were attached, one on the internal surface (internal edge) and one in the centre. Four pasteurizations were performed and the temperature and time values (every second) were stored in extension txt files through the Data Logger Software. The mean values of the pasteurization parameters were used in the diffusion model simulations in order to determine the values of thermal diffusion. Therefore, was used a numeric code developed in FORTRAN, using the studio CVF 6.6.0 on the Windows platform which was later coupled to an optimizer. The dissemination equation written in three-dimensional generalized coordinates was discredited and solved by the finite volume method with a fully implicit sequence and for the first type boundary condition. In addition, physical–chemical and microbiological analysis of the pulp of the sleeve was performed before and after pasteurization, in order to verify the effectiveness of pasteurization for containers with arbitrary geometries. The results show that there has been a reduction in total microorganisms without a significant nutritional change in the product. To sum up, the determination of the expression of the variable thermal diffusivity with the local temperature enables to define the time necessary for the whole product (with emphasis on the less favorable point), and packaged in a container with arbitrary geometry enter into thermal equilibrium at a previously defined temperature through a numerical simulations, making it unnecessary to perform further experiments whenever a new container is used to package the product.