Selective far infrared heating of food systems

A novel far infrared (FIR) heating system was designed and fabricated for selective heating of food powders such as soy protein and glucose. The FIR heating system consisted of six ceramic lamps, a cone-shaped waveguide, and an optical band pass filter selected according to the spectral absorptivities of the food powders. A bandpass filter was chosen to enable the differential heating of food components primarily due to their selective absorptivities. Selective heating of the two powders showed that protein, predominantly absorbing in the range between 6 and 11 μm could be heated up to 6°C more in 5 min of heating with the filter, compared to heating without the filter, when glucose temperature was in general higher than protein. Numerical analysis based on the different absorptivities of powders verified that the model predicted temperatures were very close to the experimental data, confirming the feasibility of the heating system.; The incident FIR radiation could be controlled to provide electromagnetic radiations in the specific spectral regions using different optical filters. Pure soybean protein and starch powder were used to test the validity of the system. The effect of three different filters having spectral distribution ranges in the regions ranging 2.50 to 2.96 μm, 3.15 to 3.67 μm, and 5.45 to 12.23 μm were evaluated. Based on the heat flux ratio between soy protein and starch, in relation to the applied spectral conditions, a temperature simulation model was developed to validate the selective heating process.; Inactivation of fungal spores such as Aspergillus niger and Fusarium proliferatum in corn meal was investigated using selective IR heating method. The selective heating method proposed to denature the protein band in the spectral range between 5.88 and 6.66 μm, showed an enhancement in the lethality of fungal spores, compared to normal IR heating. The thermal death kinetics model developed based on dynamic temperature simulations was validated.; The mechanism for the thermal death kinetics model using the selective heating concept for inactivation of fungal spores based on a dynamic temperature profile was explored. An integrated model that combines the thermal death kinetics with IR heat transfer model was developed. Model predictions of higher fungal spore temperature was validated by showing that pure dried fungal spores were heated 6°C higher than pure corn meal after 300 sec of heating. The denaturation of protein band as a target spectral region of selective heating could also partially contribute to an additional increase in the lethality of fungal spores compared to model prediction.; Pulsed UV heating was applied to fungal inactivation as a comparative method of selective IR heating. Response surface method applied for reduction of the experimental runs and optimization of the experimental conditions was validated by development of the quadratic regression equation to fit the experimentally determined log₁₀ reduction of fungal spores. Modification of pulsed UV heating system is required to maximize the intrinsic UV photochemical function in fungal inactivation with the minimization of a large amount of heat generation.