J. Agric. Food Chem., 46 (1), 206 -210, 1998. jf970670x S0021-8561(97)00670-5
Web Release Date: January 19, 1998

Copyright © 1998 American Chemical Society

Effects of Microwave Heating on the Loss of Vitamin B₁₂ in Foods

Fumio Watanabe,* Katsuo Abe, Tomoyuki Fujita, Mashahiro Goto, Miki Hiemori, and Yoshihisa Nakano

Department of Food and Nutrition, Kochi Women's University, Kochi 780, Japan, and Department of Applied Biological Chemistry, Osaka Prefecture University, Sakai 593, Japan

Received for review August 4, 1997. Accepted October 14, 1997.

Abstract:

To clarify the effects of microwave heating on the loss of vitamin B₁₂ in foods, raw beef, pork, and milk were treated by microwave heating and then their vitamin B₁₂ contents were determined according to a chemiluminescent vitamin B₁₂ assay with hog intrinsic factor. Appreciable loss (~30-40%) of vitamin B₁₂ occurred in the foods during microwave heating due to the degradation of vitamin B₁₂ molecule by microwave heating. When hydroxo vitamin B₁₂, which predominates in foods, was treated by microwave heating and then analyzed by silica gel 60 thin layer chromatography, two vitamin B₁₂ degradation products were found. One of the compounds with a R_f of 0.16 was purified and partially characterized. The vitamin B₁₂ degradation product did not show any biological activity in the growth of a vitamin B₁₂ requiring microorganism, Euglena gracilis Z, and was not bound to hog intrinsic factor, a mammalian vitamin B₁₂ binding protein. Intravenous administration of the compound (1 g/day) for 7 days to rats showed that the compound neither has toxicity nor acts as a vitamin B₁₂ antagonist in mammals. These results indicate that the conversion of vitamin B₁₂ to the inactive vitamin B₁₂ degradation products occurs in foods during microwave heating.

Keywords: Vitamin B₁₂; degradation; microwave heating; intrinsic factor; rat

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