Theoretical-experimental analysis of shrinkage: study of driyng of bananas

Author(s)

Marcel Eiki Katekawa

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Química
• Defense date: 2006-07-18

Examining board members

Maria Aparecida Silva; Carlos Alberto Carrasco Altemani; Marlene Rita de Queiroz; Osvaldir Pereira Taranto; Paulo José do Amaral Sobral

• Advisor: Maria Aparecida Silva

Abstract

The drying process may induce collateral effects in the dry material, such as the volume reduction. The objectives of this study are to investigate the characteristics of the shrinking process and to consider a strategy for inclusion of these effects in a drying simulation. Banana was chosen as a case study due to its importance in Brazil and to the existence of some studies on the shrinking process of this fruit during drying. Initially the effects of the drying conditions on the dimensional behavior of the material were analyzed. Banana slices shrink linearly in the beginning of the drying process, though some deviation of this behavior is observed for low moisture content. As banana possesses a potentially anisotropic structure, the behavior of the different tissues from the edible fruit had to be taken into consideration through the study of the glass transition of each phase. One of the tissues, the mesocarp, has a glass transition temperature of 46ºC when totally dry and may undergo glass transition during convective drying, which affects the final volume of the dried sample. Moreover, moisture compartmentalization in the interior of each tissue was analyzed and related to the differential behavior during drying. The mesocarp is more easily dried even though it possesses a higher concentration of unbound moisture. Finally, a resolution of mass and energy balance equations using unstructured meshes in order to allow a better inclusion of the shrinkage effects in drying was developed. (AU)