Some Problems in Measurements of Mechanical Properties of Tofu (Soybean Curd)

Abstract

Breaking stress has been taken as "hardness" to describe mechanical properties of tofu (soybean curd). However, "hardness" is defined as a textural property indicating the resistance to deformation by applied force. Unfortunately, a number of reports on mechanical properties of tofu have given insufficient information to compare each other's data. We have carried out puncture and compression tests of tofu and monitored the gelation process of soymilk by a dynamic viscoelastic measurement. Apparent breaking stress in the puncture test depended on plunger diameter, but in the compression test it was independent of sample diameter. The following suggestions are given in destructive tests of tofu.
1) A result should include breaking stress and breaking strain data, since breaking force (load) depends on the size of the plunger and the sample gel.
2) Shape and size of the plunger and the samples and test temperature should be shown, because they affect the breaking properties of tofu.
3) Since a fairly long time is required to form a complete gel structure of tofu, a test should use samples which are aged sufficiently after coagulant addition.