Variation in the Calcium and Magnesium Contents of Tofu and a Comparison of their Contents with Values in the Standard Tables of Food Composition in Japan(5th Revised Edition).

Oku Tsuneyuki, Bong Jang Eun, Nakamura Sadako, Yoda Mayumi, Arikawa Mika, Muto Keiko

doi:10.5264/eiyogakuzashi.60.189

The Ca content of traditional tofu was clearly rich, because CaSO₄ is used as a coagulant. However, the Ca content of contemporary tofu was found to be poor due to Mg salt or saccharic acid being used as the coagulant. In order to learn more about this variation, the Ca and Mg contents were measured for Momen tofu (regular tofu, n=22), Kinugoshi tofu (tofu with whey, n=13) and pre-packed tofu (n=12) sold in four areas of Nagasaki prefecture. These measured contents were compared with those in the Standard Tables of Food Composition in Japan (5th revised edition). The contents of Ca and Mg greatly varied with the same type of product from different manufacturers and among the three different types of tofu. The Ca content was negatively correlated with the Mg content in all tofu samples (p<0.01). This result is due to the fact that Momen tofu, in which CaSO₄ was used, did not use Mg salt as the coagulant, while pre-packed tofu, in which Mg salt was used, did not use CaSO₄ as the coagulant. 60% of the Momen tofu samples had a Ca content lower than that in the standard tables, and the figure for one-third of all Momen tofu samples was less than 30% of that in the standard tables. In contrast, the Mg content of all Momen tofu samples was higher than that in the standard tables. The Ca and Mg contents of all Kinugoshi tofu and pre-packed tofu samples were more than those in the standard tables. These results indicate that it is important to read the labels and to choose the kind of tofu when it is to be used in a menu as the Ca source.

Variation in the Calcium and Magnesium Contents of Tofu and a Comparison of their Contents with Values in the Standard Tables of Food Composition in Japan(5th Revised Edition).

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