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

Abstract

To clarify the effects of microwave heating on the loss of vitamin B(12) in foods, raw beef, pork, and milk were treated by microwave heating and then their vitamin B(12) contents were determined according to a chemiluminescent vitamin B(12) assay with hog intrinsic factor. Appreciable loss ( approximately 30-40%) of vitamin B(12) occurred in the foods during microwave heating due to the degradation of vitamin B(12) molecule by microwave heating. When hydroxo vitamin B(12), which predominates in foods, was treated by microwave heating and then analyzed by silica gel 60 thin layer chromatography, two vitamin B(12) degradation products were found. One of the compounds with a R(f)() of 0.16 was purified and partially characterized. The vitamin B(12) degradation product did not show any biological activity in the growth of a vitamin B(12) requiring microorganism, Euglena gracilis Z, and was not bound to hog intrinsic factor, a mammalian vitamin B(12) binding protein. Intravenous administration of the compound (1 µg/day) for 7 days to rats showed that the compound neither has toxicity nor acts as a vitamin B(12) antagonist in mammals. These results indicate that the conversion of vitamin B(12) to the inactive vitamin B(12) degradation products occurs in foods during microwave heating.

Loss of Vitamin B12 in Fish (Round Herring) Meats during Various Cooking Treatments

“…Our previous studies have demonstrated that appreciable loss (~40%) of B 12 occurs in certain foods during microwave heating (9). Prolonged heat-treatments (boiling for 30 min or microwaving for 6 min) of authentic OH-B12 solution have demonstrated the accelerated formation of B12 degradation products, some of which are identified as the compounds with various changes to lower-ligand moiety (cobalt-coordinated nucleotide) (9,17).…”

“…Our previous studies have demonstrated that loss of B 12 significantly occurs in beef, pork, and milk during microwave heating ( 9 ). Although the effects of various cooking methods on the proximate composition, mineral, and vitamin (A, E, B 1 , naiacin, and B 6 ) contents of certain fish fillets have been investigated ( 10 ), it is still unclear how much B 12 is lost in raw fish meats during cooking; the lack of this information may be due to the difficulty of B 12 assay in foods.…”

Reduction of plasma homocysteine and serum methylmalonate concentrations in apparently healthy elderly subjects after treatment with folic acid, vitamin B12 and vitamin B6: a randomised trial

“…This might be due to an increased prevalence of atrophic gastritis (Streeter et al, 1976;Ihamäki et al, 1979;Krasinski et al, 1986;Carmel et al, 1987;Jones et al, 1987) and certain medicaments (Adams et al, 1983;Belaiche et al, 1983;Kittang & Schjönsby, 1987;Lindstedt, 1999). The extent of vitamin B 12 malnutrition in the elderly is unknown but concern relates to the observation that microwave heating of food can cause degradation of hydroxo-cobalamin (Watanabe et al, 1998).…”

Opportunistic Screening of Vitamin B12 Deficiency in IT Professionals Presenting for Routine Health Check-up

“…As many as 33 subjects amongst non vegetarian group, were eating such nonveg diet only on occasional basis. Further, some traditional ways of cooking, may be responsible for partial degradation of vitamin B12 [9].…”