Abstract
The development of swelling of rehydrated Kori-tofu was studied. The results obtained were as follows.
(1) The development of swelling of rehydrated Kori-tofu occurred with the removal of ammonia held in Kori-tofu into rehydration solution.
(2) Ammonia fixed in Kori-tofu treated with ammonia gas and stored for a long time, became non-soluble, and couldn't take part in the swelling of Kori-tofu as rehydrated.
(3) When Kori-tofu was rehydrated with several kinds of alkali solution (NH4 OH, NaOH, Ca(OH)2), it swelled with the increase of the concentration of the solution (beyond 0.1M), and beyond pH 9.
(4) Kori-tofu swelled in the alkaline solution showed shrinkage with the addition of acid to it, but its volume was ever larger than that of rehydrated Kori-tofu as control. This will be the reason why it doesn't shrink when treated with water in cooking.
(5) Ammonia treated Kori-tofu, from which most of ammonia liberated with its long storage, swelled similarly by repeated treatment with ammonia gas.
(6) No significant differences were recognized between proteins in ammonia treated Kori-tofu and the control, as observed from the result of SH group and the digestibility with pepsin.
