Studies on the Browning of Kori-tofu |
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Authors: | Seiichi Homma Nobuko Suzuki Hiromichi Kato Masao Fujimaki |
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Institution: | Department of Agricultural Chemistry, Faculty of Agriculture, The University of Tokyo, Tokyo |
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Abstract: | Kori-tofu was stored under RH 95% at 60°C and the changes of its nitrogenous compounds in the course of browning were examined. The water-soluble and 10% TCA-soluble fractions prepared from the ether extraction residue of Kori-tofu were analyzed. The nitrogen content of water-soluble fraction temporarily decreased and then increased gradually in the course of browning, while that of 10% TCA-soluble fraction increased gradually during the browning process. Amino acid analyses of 10% TCA-soluble fraction and its hydrolyzate revealed that no free amino acid was detected in unbrowned Kori-tofu, whereas in browned Kori-tofu occurred peptides, ammonia and free amino acids such as aspartic acid, serine, glutamic acid, glycine and alanine.Free amino acids similar to those detected in browned Kori-tofu occurred in the model system consisting of lysozyme and methyl linoleate, crotonaldehyde, glyoxal, methyl-glyoxal and also the brown substance prepared from glycine and methyl linoleate during storage. The formation mechanism of free amino acids from proteins was discussed. |
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