The “tokoroten” (gelidium jelly) which is an intermediate product during the manufacturing process of agar is often spoiled in the mild winter, and subsequently the quality of agar manufactured is depressed. This is called the “dankan” phenomenon.
In the present paper, the authors examined both organoleptic and physico-chemical changes of “tokoroten” during spoliage and the effect of spoilage on the quality of agar prepared. The results obtained are as follows:
(1) Physico-chemical properties of “tokoroten” change largely during the progress of spoilage and the quality of agar prepared is affected by these changes; the reducing sugar increases slowly but the relative viscosity and the jelly strength decrease rapidly during spoilage (Table 3, 4, 5 and 6).
As these changes especially the latter two parallel with that of organoleptic observations, it is assumed possible to assign three grades for the spoilage in terms of the ratio of relative viscosity to jelly strength (Fig. 5).
(2) Some causative microörganisms in the spoilage were separated from spoiled “tokoroten”, agar and other materials. They were chromobacteria producing red, orange, yellow and yellowish orange pigments, and one of them was an agar-decomposing bacterium. It is inferred that these bacteria are substantially derived from the tainted reed mat on which “tokoroten” is laid.
Therefore, it is necessary for the manufactures to sterilize the reed mat by any means in order to prevent “tokoroten” from spoilage in the mild winter.