Food Properties
CHAPTER 4
THERMODYNAMICAL,
THERMOPHYSICAL, AND
RHEOLOGICAL PROPERTIES OF
FRUITS AND FRUIT PRODUCTS
4.1. INTRODUCTION
Most processed and many freshly consumed fruits receive some type of heating or cooling during handling or manufacturing. Design and operation of processes involving heat transfer needs special attention due to heat sensitivity of fruits. Both theoretical and empirical relationships used when designing, or operating, heat processes need knowledge of the thermal properties of the foods under consideration. Food thermal properties can be defined as those properties controlling the transfer of heat in a specified food. These properties are usually classified (Perry and Green, 1973) into thermodynamical properties, viz, specific volume, specific heat, and enthalpy; and heat transport properties, namely, thermal conductivity and thermal diffusivity.
When considering the heating or cooling of foods, some other physical properties must be considered because of their intrinsic relationship with the ‘‘pure’’ thermal properties mentioned, such as density and viscosity. Therefore, a group of thermal and related properties, known as thermophysical properties, provide a powerful tool for design and prediction of heat transfer operation during handling, processing, canning, and distribution of foods
(Fig. 4.1). Abundant information on thermophysical properties of food (Polley et al., 1980;
Wallapapan et al., 1983; Choi and Okos, 1986; Rahman, 1995) is available to the design engineer. However, finding relevant data is usually the controlling step in the design of a given food operation, and the best solution may be the experimental determination.
This chapter provides data and information for thermal process calculation for fruits and fruit products, including a brief description of more commonly used methods for measurement and determination of thermophysical properties.
4.2. THERMOPHYSICAL PROPERTIES’ IDENTIFICATION
Thermophysical
THERMODYNAMICAL,
THERMOPHYSICAL, AND
RHEOLOGICAL PROPERTIES OF
FRUITS AND FRUIT PRODUCTS
4.1. INTRODUCTION
Most processed and many freshly consumed fruits receive some type of heating or cooling during handling or manufacturing. Design and operation of processes involving heat transfer needs special attention due to heat sensitivity of fruits. Both theoretical and empirical relationships used when designing, or operating, heat processes need knowledge of the thermal properties of the foods under consideration. Food thermal properties can be defined as those properties controlling the transfer of heat in a specified food. These properties are usually classified (Perry and Green, 1973) into thermodynamical properties, viz, specific volume, specific heat, and enthalpy; and heat transport properties, namely, thermal conductivity and thermal diffusivity.
When considering the heating or cooling of foods, some other physical properties must be considered because of their intrinsic relationship with the ‘‘pure’’ thermal properties mentioned, such as density and viscosity. Therefore, a group of thermal and related properties, known as thermophysical properties, provide a powerful tool for design and prediction of heat transfer operation during handling, processing, canning, and distribution of foods
(Fig. 4.1). Abundant information on thermophysical properties of food (Polley et al., 1980;
Wallapapan et al., 1983; Choi and Okos, 1986; Rahman, 1995) is available to the design engineer. However, finding relevant data is usually the controlling step in the design of a given food operation, and the best solution may be the experimental determination.
This chapter provides data and information for thermal process calculation for fruits and fruit products, including a brief description of more commonly used methods for measurement and determination of thermophysical properties.
4.2. THERMOPHYSICAL PROPERTIES’ IDENTIFICATION
Thermophysical
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