Abstract
Rheological analysis of “body” or consistency of “yokan” (pasty food made from gelation of concentrated starch suspension in sugar solution by agar-agar) was done by using a curdometer.
Thirty samples of yokan from various makers were tested.
As a first step, they were classified into three groups, i.e., good, medium, and poor, according to their practical evaluation, e.g., “body”, stiffness or consistency.
The curdometer used was a modified penetrometer. A small circular disk is pushed into the sample paste by means of a spring. Penetration of the disk is recorded on a drum. From observation of the recorded curves, it is possible to evaluate elastic deflection, plastic yielding or viscous flow of the paste.
High grade yokan of good body is characterized by high viscosity and a sort of strain-hardening. Yokans of poor body, on the other hand, show continuous flow after plastic yielding.
Their mechanical properties were compared with their compositions and chemical constituents. Sufficiently high value of starch and sugar content is necessary for the appearance of good body.
Rheological data, so acquired and properly analysed, were used effectively in the design of a continuous processing plant of yokans.
