豆类发酵食品中维生素B_(12)的分离与定量

植物性食物不含维生素B_(12),但我们曾发现发酵食品中可检出维生素B_(12)活性物质。为了进一步确定这类食品中具有生理作用的钴维生素含量,建立了维生素B_(12)生物自显谱面积定量法,其要点如次:豆类发酵食品提取液点于滤纸上,以仲丁醇—水—氢氧化铵—5％氰化钾(100:50:1:0.25)为扩展剂,下行扩展,24—72小时后取出干燥,然后置于含有E、Coli44110及2,3,5—三苯基四唑(鎓)化氯的营养琼脂培养基上,显谱后测量生长圈面积,计算样品中钴维生素含量。 用上述方法测定了两种豆类发酵食品,其钴维生素含量均值:每百克臭豆付乳中含0.97μg,酱豆付乳含0.4μg。与动物性食品相比,这两种豆类发酵食品可视为维生素B_(12)较好来源。

ISOLATON AND DETERMINATION OF VITAMIN B_(12) IN FERMENTED SOYBEAN FOODS

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 follows:The 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 μg/100g sample, fermented soybean curd contains 0.41 μg/100g sample. Compared with animal foods, both types of fermented soybean foods may be considered as good source of vitamin B12.