Thermal properties of foods

Reidy, G. A. 1968. I. Methods for Determining Thermal Conductivity and Thermal Dif-fusivity of Foods. II. Values for Thermal Properties of Food Gathered from the Literature. Department of Food Science, Michigan State University, Lansing, Michigan, p. 77. 

ASHRAE, Thermal properties of foods, ASHRAE Handbook Refrigeration, Atlanta, 2002, chap. 8. 

Mohsenin, N.N., Thermal Properties of Foods and Agricultural Materials, Gordon and Breach, New York, 1980. 

Murakami, E.G. and Okos, M.R., Measurement and prediction of thermal properties of foods, in Food Properties and Computer-Aided Engineering of Food Processing Systems, Singh, R.P. and Medina, A.G. (eds.), Kluwer Academic Publishers, Boston, MA, 1989, pp. 3-48. 

Rha, C., Thermal properties of food materials, in Theory, Determination and Control of Physical Properties of Food Materials, Rha, C. (ed.), D. Reidel Publishing Company, Boston, MA, 1975, pp. 311-355. 

CHAPTER 2. THERMAL PROPERTIES OF FOODS. FROM THE FREEZING PRESERVATION OF FOODS. VOLUME 2. 

In many cases the temperature of a process that is varying continuously with time is determined experimentally by measuring the temperature in the slowest-heating region. In cans this is the center of the can. Methods given in Chapter 5 for unsteady-state heating of short, fat cylinders by conduction can be used to predict the center temperature of the can as a function of time. However, these predictions can be somewhat in error, since physical and thermal properties of foods are difficult to measure accurately and often can vary. Also, trapped air in the container and unknown convection effects can affect the accuracy of predictions. 

Differential scanning calorimetry (DSC) is the main approach used today for studying thermal properties of foods (phase transitions, reactions, and specific heats). Older systems, such as containers fitted with sensors that follow the rising temperature of a heating bench, autoclaves with additional pressure sensors, or (high pressure) differential thermal analysis (DTA) instruments, are still useful. Modulated DSC is also applied today to food studies [4-9],... 

Singh, N., Chawla, D., Singh, J. (2004a). Influence of acetic anhydride on physicochemical, morphological and thermal properties of eorn and potato starch. Food Chem., 86, 601-608. 

Polymer-clay nanocomposites (PCN) are a class of hybrid materials composed of organic polymer matrices and organophilic clay fillers, introduced in late 1980s by the researchers of Toyota (Kawasumi, 2004). They observed an increase in mechanical and thermal properties of nylons with the addition of a small amount of nano-sized clays. This new and emerging class of pol miers has found several applications in the food and non-food sectors, such as in constmction, automobiles, aerospace, military, electronics, food packaging and coatings, because of its superior mechanical strength, heat and flame resistance and improved barrier properties (Ray et al., 2006). 

Table 1. Dielectric and Thermal Properties of Common Foods...

Thermal Properties of Melhyl Chloride, Food Investigation Board, Dept. Sou Ind. Research (Great Britain), No. 19 (1924) von Siemens,... 

The physical/chemical states and the thermal transitions of food materials determine the process conditions, functionality, stability and overall quality, including the texture, of the final food products. Carbohydrates and proteins— two major biopolymers in various food products—can exist in an amorphous metastable state that is sensitive to moisture and temperature changes (Cocero and Kokini 1991 Madeka and Kokini 1994, 1996). The physical states of components in a biopolymer mixture determine the transport properties, such as viscosity, density, mass and thermal dif-fusivity, together with reactivity of the material. 

Sobral, P.J.A., Menegalli, F.C., Hubinguer, M.D., and Roques, M.A. Mechanical, water vapor barrier and thermal properties of gelatin based edible films. Food Hydrocolloids, 15, 423, 2001. 

Hayakawa, J.J. and Nakai, S. 1985. Contribution of hydrophobicity, net charge and sulfhy-dryl groups to thermal properties of ovalumin. Canadian Institute of Food Science and Technology Journal 18 290-295. 

Srinivasan, S., Xiong, Y.L., and Blanchard, S.P. 1997a. Effect of freezing and thawing methods and storage time on thermal properties of freshwater prawns (Macrobrachium rosenbergii). Journal of the Science of Food and Agriculture 75 37-44. 

Ahmed J, Varshney SK, Auras R. Rheological and thermal properties of polylactide/silicate nanocomposites J Food Sci. 75(2) (2010) N17-N24. 

The transport properties of foods received much attention in the literature [184-188]. The main results presented by Saravacos and Maroulis [188] are summarized in this section. The results refer to moisture diffusivity and thermal condnc-tivity. Recently published values of moisture diffusivity and thermal conductivity in various foods were retrieved from the literature and were classified and analyzed statistically to reveal the influence of material moisture content and tempera-tnre. Empirical models relating moisture diffusivity and thermal conductivity to material moisture content and temperature were fitted to all examined data for each material. The data were screened carefully using residual analysis techniques. A promising model was proposed based on an Arrhenius-type effect of temperature, which uses a parallel structural model to take into account the effect of material moisture content. 

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