ISOLATON AND DETERMINATION OF VITAMIN B_(12) IN FERMENTED SOYBEAN FOODS / 营养学报

ABSTRACT

Foods derived from plants are thought to be devoid of vitamin B12. We have found that some fermented foods contained microbiologically active vitamin B12 components.In order to ascertain the amount of physiological active vitamin B12, we have established a bioautographic area quantitative method of determination of vitamin B12. The procedure is described briefly as followsThe extract of fermented soybean food sample is spotted on a filter paper strip. The Paper is developed with a mixture of secbutanol-water-ammonia water- 5 % potassium cyanide (100 50 1 0.5) using descending technique. After developing for 24-72 hours, the strip is taken out and dried in air. It is then put on the surface of nutrient agar containing E. coli 44110 and 2,3,5,-triphenyl tetrazolium chloride. After incubation, the area of spot of growth is measured and the amount of vitamin B12 in the sample is calculated.Two types of fermented soybean food samples were assayed by the above procedure, mean values of vitamin B12 content are fermented soybean curd with strong smell contains 0.97 ?g/100g sample, fermented soybean curd contains 0.41 ?g/100g sample. Compared with animal foods, both types of fermented soybean foods may be considered as good source of vitamin B12.