17H-7 |
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M. SUPARNO1, K. D. Dolan2, and P. K. W. Ng2. (1) Dept. of Agricultural Engineering, Michigan State Univ., 218 A.W. Farral Hall, East Lansing, MI 48824-1323, (2) Dept. of Food Science & Human Nutrition/Dept. of Agricultural Engineering, Michigan State Univ., 208 G. Malcolm Trout FSHN Bldg., East Lansing, MI 48824-1224 Typical methods to obtain thermal kinetic parameters at atmospheric heating conditions have been published. However, heating at these conditions and temperatures higher than 100°C could cause moisture loss if the container is not perfectly sealed. Conversely, heating sealed containers could cause dangerous pressure build-up under uncontrolled pressure conditions. We hypothesize that the moisture loss problem can be solved by correcting the high-temperature parameters based on a lower temperature heating study. Our objective was to compare the thermal kinetic parameters of thiamin in flour obtained from two high-temperature heating methods, conducted at: 1) atmospheric pressure (AP) conditions with moisture correction; 2) controlled pressure (CP) conditions. Wheat flour with 0.3% (w/w) thiamin, at 25% (w/w) moisture was used. At AP conditions, flour in thin steel cells was heated at 140, 155 and 160°C in an oil bath. Moisture loss was significant. To obtain the moisture correction factor, a constant-moisture study was conducted at 80°C using seven moisture contents (5-26%). For the second method, flour in double-seamed cans was heated in a CP steam retort at 130°C. Thiamin content in heated samples was analyzed using a fluorometer. For the AP method, the corrected activation energy was 125 kJ/g-mol and reaction rate at 130°C was 1.94E-3 1/s. Using the CP method, the activation energy and reaction rate were 155 kJ/g-mol and 4.3E-4 1/s, respectively. The difference in reaction rates suggested that correcting high-temperature parameters based on a constant moisture study at lower temperature might not generate the correct high-temperature parameters. This result may be due to variation in thiamin activation energy with temperature. The CP heating method required more complicated setup and analysis than the AP method. However, the kinetic parameters for thiamin obtained from the CP method were more accurate because constant moisture was achieved even during high- temperature heating.
Session 17H, Food Engineering: Thermal processes
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