ABSTRACT
Mass-volume-area-related properties are one of ve groups (acoustic, mass-volume-arearelated, morphological, rheological, and surface) of mechanical properties (Rahman and McCarthy, 1999). These properties are needed in process design, for estimating other properties, and for product characterization or quality determination. The geometric characteristics of size, shape, volume, surface area, density, and porosity are important in many food materials handling and processing operations. Fruits and vegetables are usually graded depending on size, shape, and density. Impurities in food materials are separated by density differences between impurities and foods. Knowledge of the bulk density of food materials is necessary to estimate oor space during storage and transportation (Mohsenin, 1986; Rahman, 1995). When mixing, transportation, storing, and packaging particulate matter, it is important to know the properties of bulk material (Lewis, 1987). The surface areas of fruits and vegetables are important in investigations related to spray coverage, removal of residues, respiration rate, light reectance, and color evaluation, as well as in heat-transfer
1.3.1.3 Particle Density 13 1.3.1.4 Bulk Density 14
1.3.2 Measurement Techniques of Porosity 14 1.3.2.1 Direct Method 14 1.3.2.2 Optical Microscopic Method 14 1.3.2.3 Density Method 14
1.3.3 Surface Area 14 1.3.3.1 Boundary Surface Area 14 1.3.3.2 Pore Surface Area 15 1.3.3.3 Cross-Sectional Area 16
1.4 Specic Data 16 1.4.1 Predictions of Density 16
1.4.1.1 Gases and Vapors 16 1.4.1.2 Liquid Foods 17 1.4.1.3 Density of Solid Foods 18
1.4.2 Predictions of Porosity 21 1.4.3 Prediction of Surface Area 24
1.4.3.1 Euclidian Geometry 24 1.4.3.2 Non-Euclidian or Irregular Geometry 24 1.4.3.3 Theoretical Prediction 25 1.4.3.4 Size Distribution 28
1.5 Summary 31 Acknowledgments 31 List of Symbols 31
Greek Symbols 32 Subscripts 33 Superscripts 33
References 33
studies in heating and cooling processes (Mohsenin, 1986). In many physical and chemical processes, the rate of reaction is proportional to the surface area; thus, it is often desirable to maximize the surface area. Density and porosity have a direct effect on the other physical properties. Volume change and porosity are important parameters in estimating the diffusion coefcient of shrinking systems. Porosity and tortuosity are used to calculate effective diffusivity during mass transfer processes. Mechanical properties of agricultural materials also vary with porosity. This chapter provides terminology, measurement techniques, and prediction models of selected mass-volume-area-related properties.
