There are very few studies in the literature on the infrared process and its impact on food nutrients. However, some of it is reported here. Comparisons between conventional heating techniques and infrared heating give some hints as to their effect on the nutritional value of heated products.
Recent studies of intense IR radiation treatment on nutritional value and anti-nutritional factors of cereals (corn, rice, brown sorghum) and common beans show that digestibility and energy values were not altered significantly but protein quality decreased (Keya-EL and Sherman U, 1997). No anti-nutritional factors were found in rice. Tannin in sorghum was denatured extensively by IR treatment. Small amounts of aflatoxins in corn and sorghum trypsin inhibitors in common beans were destroyed.
Mackerel were dried in IR radiation at 180°C for 40 minutes and the results revealed better nutritional values than after conventional treatment (Shyue-Bin-Ho, En-Chie-Lin, Fu-Jin-Wang and Sheu-Der-Wu, 1996). The Maillard reaction in the crust of bread or meat can be better controlled when using NIR heating than using grilling or frying or in an ordinary baking oven. This is due to the fast response when changing the energy levels of radiators. However, too high energy transfer at the start of the process may give white spots of ungelatinised starch.
As the IR heating technique in most applications shows shorter drying, frying or heating times for food nutrition, spoilage is less than that of most conventional techniques. The spoilage can also be controlled in a better way. Knowing the kinetics of the chemical reaction of different nutritional components and using mathematical models based on knowledge about the IR heating temperature and mass transfer is one way to optimise the nutritional value of the ready-made product (Skjoldebrand, 2000).
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