暖冬期における寒天の変敗防止に関する研究-IX

トコロテンのpH価調整による“ダンカン”防止について

抄録

The present study was designed to ascertain the effects of lowering pH value of “tokoroten” on the growth of organisms and on the spoilage of “tokoroten” and agar. In this study, the effects of sulfuric acid on the jelly strength of “tokoroten” and agar and on the occur-rence of discoloration during the storage of agar, were also examined.
The results obtained are shown in Tables 1-9, and summarized as follows:
1) The growth of Pseudomonas lacunogenes, which is an agar decomposing bacterium and causative principally in the spoilage, is remarkably inhibited below pH 5.3.
2) In the mixed culture of bacteria isolated from the spoilt “tokoroten”, their growth is remarkably inhibited below pH 4.5.
3) In order to prevent the spoilage of “tokoroten”, the lowering pH value of “tokoroten” is remarkably effective.
4) The “tokoroten” having lower pH value is not different from that having the usual pH value with respect to the jelly strength, but the jelly strength of the former decreases considerably in comparison with one of the latter, when both “tokoroten” are dissoluted by heating and are recoagulated. The agar prepared from the former also is not different from that prepared from the latter in the jelly strength.
Therefore, sulfuric acid for lowering pH value should be added to “tokoroten” sol after the process of filtering.
5) Agar prepared from such a “tokoroten” is discolored with the lapse of time during the storage, but it is bleached from this discoloration if it is treated for 60 minutes by the 1/1, 000 solution of sodium hypochlorite as available chlorine.