Heating of foods

Heating of foods may be moderate, such as pasteurizing at temperatures of 65-88 °C, intermediate, such as thermal processing (canning) at temperatures of 88-121 °C, or high, such as frying at approximately 177 °C or oil deodorizing at... 

Heating of foods rich in proteins may lead to formation of crosslinking isopeptide bonds between the S-NH2 group of lysine and the p- and y-carboxyl groups of aspartic and glutamic acid residues or their amides. 

Buffler, C. and Stanford, M. 1991. The effects of dielectric and thermal properties on the microwave heating of foods. Microwave World 12(4) 15. 

Conventional heating and microwave heating of food products result in significantly different end products. Foods heated conventionally are subjected to relatively high surface temperatures, 350-450 degrees F., which results in product surface dehydration. 

Transfer of substances will also depend on the time and temperature of storage and/or processing or heating of food in 2° packaging. For a given substance, the lower the temperature, the lower the rate of transfer will be and, conversely, the higher the temperature, the higher the rate of transfer. 

Very severe heating of foods, at much higher temperatures and times than those required for sterilization, may lead to formation of isopeptide cross-links between the free NH2 group of Lys and the carboxylic group of Asp or Glu ... 

Piyasena, P., Dussault, C., Koutchma, T, Ramaswamy, H. S., Awuah, G. B. (2003). Radio frequency heating of foods Principles, applications and related properties - A review. Critical Reviews in Food Science, 43, 587-606. 

Foodstuffs contain much water. Many people believe the water content is responsible for the microwave heating of food. According to Fig. 1.15, dielectric relaxation of water and corresponding dielectric losses are quite negligible for ionic solutions. Conduction losses are preponderant. Ionic species such salts (sodium chloride) induce dielectric losses in soup and microwave heating results from ionic conduction. 

Irudayaraj, J. and S.J. Jun, 2000. Automatic infrared system for selective heating of food. 2000 IFT Annual Meeting, Dallas, TX. 

A more general equation to calculate the specific heat of food from the specific heat of its constituents is given by... 

Gordon, C. and Thome, S., A computerized method for determining the thermal conductivity and specific heat of foods from temperature measurements during cooling, J. Food Eng., 11 175-185 (1990). 

J R Bows, Variable fi-equency microwave heating of food , J of Microwave Power and Electromagnetic Energy, 1999 34(4) 227-238. 

Bows J R (1999) Variable frequency microwave heating of food, J Microw Power Electromagn Energ 34 227-238. 

It is evident that calorimetric techniques are often used to determine the specific heats of foods. The methods, and a synthesis of the results, are presented in the literature [113]. 

Most food science smdents learn about the Maillard reaction in one of their food chemistry coiteses. They typically learn about this reaction in the context of either nutritional losses (e.g., the loss of essential amino acids or loss of digestibility) or color formation. It should be recognized that nutritional loss and color formation are generic in the sense that the heating of foods under nearly any conditions will result in the loss of nutritional quality and in color formation. However, the reactions... 

Volumetric heating of food by internal heat generation, and without the limitations and non-uniformities of the eonventional heat. 

Schreier, P. J. R Reid, D. G Fryer, P. J. Enhanced diffusion during the electrical heating of foods. International Journal of Food Science and Technology, 28, 249—260, 1993. 

The toxic compound acrylamide is one of the volatile compounds formed during the heating of food (cf. 9.7.3). Model experiments have shown that it is produced in reactions of asparagine with reductive carbohydrates or from the resulting cleavage products (e. g., 2-butanedione, 2-oxopropanal). 

With the 2,3-enediol, not only water elimination at C-4, but also the elimination of the hydroxyl group at C-1 is possible (Formula 4.39). This reaction pathway gives, among other compounds, 3,5-dihydroxy-2-methyl-5,6-dihydropyran-4-one, which is also used as an indicator for the heating of food. The formation of two different enediols is the reason for the wider product spectrum from ketoses, like fructose, than from aldoses. In the presence of amino compounds, all the reactions mentioned here proceed very easily also in the pH range 3-7. Since free amino acids are present in many foods, the reactions shown here also occur in connection with the pathways discussed in 4.2.4.4. 

Cookers, cooking equipment or other equipment or installations used for the heating of food provide a range of sources of ignition and fuel have the potential to initiate and exacerbate a fire. 

H. Zhang, and A. K. Datta, Coupled electromagnetic and thermal modeling of microwave oven heating of foods, Journal ofMicrowave Power Electromagnetic Energy, 35(2) (2000), 71-86. 

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