抄録
It is a well accepted fact that the effect of a certain preservative can be attributed to its specific action against spoilage bacteria. And many efforts have been paid for finding out non-toxic compounds capable of inhibiting the growth of microorganisms responsible for food decomposition. However, it may be also important to fortify the action of known preservatives by improving the method of application. The purpose of the present study is to ascertain whether or not the mixing. of two prerervatives can develop more effective inhibition than a single application of each preservative used for mixing.
In the present test, formula of inhibition coefficient is defined as follows:
H=1-Tc/T
where H=coefficient of growth inhibition.
Tc=time required for bacteria to reach a definite growth showing 0.1 of the turbidity of a cultural medium (viable counts, 4×lO7/c. c, see Fig. 1).
T=time required for bacteria to reach the same turbidity of the medium, in which the test preservative is added.
Examining the inhibiting effect of some preservatives (Table 1) on the growth of bacteria, it has been ascertained that there are two types of growth-inhibition. An obvious example of type I is sodium nitrite, though most of other preservatives tested were found to belong to this type as well. The only exceptions are two sulphonamides, which indicate type II of the growth-inhibition (Fig. 2). To clarify the quantitative relationship existing between the growth-inhibition and concentration of preservatives, the concentration-inhibition curves have been sought from the growth curves of bacteria in the presence of preservatives (Fig. 3).
The result reavled that there is a tendency to increase in effect of inhibition against bacterial growth by a proper combination of two preservatives (Fig. 5).
