A mapping approach to assess the evolution of pores during dehydration

Abstract

Shrinkage and collapse phenomena are the two mechanisms involved in the evolution of pores within food products during dehydration. These phenomena can be mathematically represented by shrinkage and collapse functions, which can be derived from theoretical models of porosity, bulk density, or volume reduction coefficient. In this contribution, these two functions were simplified to capture four extreme scenarios of dehydration, which consist in the combination of total or no shrinkage with total or no collapse. The four simplified equations were used to generate theoretical maps characterized by three distinct zones that are associated with pore evolution. Each of these zones represents a key dehydration situation. By superimposing experimental data of porosity, bulk density, or volume reduction coefficient on these theoretical maps, it is possible to assess dehydration processes, i.e., drying technologies and/or dehydration conditions, in terms of pore formation and evolution over time. These theoretical maps can be constructed for each food product before starting the dehydration processes. Therefore, when the experimental data is available, the suggested mapping approach is a simple, fast, and reliable tool to: (i) assess the performance of a given dehydration process versus specific cases of pore formation, and (ii) compare different dehydration processes in terms of their ability to promote pore formation. This practical tool can be used by the industry and academia to quantitatively evaluate how far a drying technology and/or its dehydration conditions are from the ideal scenario in terms of pore formation. This gap quantification will provide a basis for converging towards the ideal scenario by fine-tuning the dehydration conditions or choosing the appropriate drying technology.

Keywords: Bulk density; Collapse; Dehydration; Mapping; Pore formation; Porosity; Shrinkage.