Mass-Volume-Area-Related Properties of Foods

Mass-volume-area-related properties are one of five groups (acoustic, mass-volume-area-related, 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 floor 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). Surface areas of fruits and vegetables are important in investigations related to spray coverage, removal of residues, respiration rate, light reflectance, and color evaluation, as well as in heat transfer 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 coefficient 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.