Abstract
“So, ” a kind of ancient milk product in Japan, was a food preservable at least for 4 months after manufacturing. Paying an attention to the water activity, a trial to reproduce the “So” was carried out. An isothermal-adsorption like curve was obtained from the measurements of water activity and water contents. On the basis of this results, three types of “So” were prepared as follow : S-14, concentrated to 14 % (limit of heat concentration); S-18, concentrated to 18 % (same water contents as cheese); S-16, concentrated to 16 % (intermediate between S-14 and S-18). Changes in the appearance, water activity and water contents of the samples were investigated during storage.
In the case of S-16 and S-18, the growth of molds was observed on the 10th day during storage and their water activities were 0. 90-0. 94, respectively. On the other hand, the growth of molds was not observed in the S-14 even after the storage for 1 month in the beaker. In this case, the water activity was maintained below 0. 80 and water content was a low value of 10 %. Additionally, it was possible to store S-14 sample for long times in the jar, as water activity of S-14 possessed low value (0. 65) after 4 months.
It was found from the above results that “So” could be prepared by concentrating raw milk to less than 14 % in ancient Japan which had no storage technology.
