Figure 7 Curve showing action of koji extract on gelatinized starch at 45C

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Time in hours.

Time in hours.

At a higher temperature, 60°C, the activity of the koji solution is very soon exhausted, as will be seen from the following results (Table 21), and from the curve in Figure 8. 10 grams of starch and 10 grams of koji were used.

The number found at 15 minutes is doubtless incorrect. After half an hour had elapsed, and the specific rotatory power had diminished to 168°, the action appeared to cease, until a fresh addition of koji was made, when it fell at a similar rate, and for nearly the same time as at first. The high temperature, therefore, very quickly renders the diastase of koji inactive.

At a temperature of 70°C practically no solution of starch took place from which it may be concluded that a temperature between 60° and 70°C renders it completely inert. The diastase of malt is not killed until between 80° and 81°, which constitutes another point of difference between the two. The two bodies resemble one another in this, that the loss of activity is accompanied by the appearance of a distinct precipitate, consisting of albumenoid matter that has been coagulated by heat. Messrs. Brown and Heron state that

Figure 8: Curve showing the action of koji extract on gelatinized starch at 60°C

Figure 8: Curve showing the action of koji extract on gelatinized starch at 60°C

Time in hours.
Table 22: Action of Koji on starch at 60°C

Time

Total starch in solution (koji deducted)

Specific rotatory power of starch

5 minutes

9.70 grams

182.1°

15

"

180.2

30

"

168

1 hour

"

168

1-1/2

"

164.6

2 hours

10.19

145.8

2-1/2

"

131.8

3

"

128.2

3-1/2

"

131.8

4

10.19

131.8

"Every stage in the coagulation of malt extract by heat is attended with a distinct modification of its starch transforming power; and conversely, we have never been able to discover any modification in starch transforming power which is not attended with distinct coagulation. In addition to this, at 80-81°, the point at which the diastatic power of malt extract is destroyed, nearly the whole of the coagulable albumenoids have been precipitated. We are consequently led to conclude that the diastatic power is a function of the coagulable albu-menoids themselves, and is not due as has been generally supposed, to the presence of a distinctive transforming agent."*

We have already seen that the principal change which rice undergoes in its conversion to koji is the alteration in the nature of the albumenoid matter which becomes more easily degraded and soluble in water; taking this in connection with the destruction of the active properties of the solution at a temperature corresponding to that at which the albumenoid matter becomes coagulated, we are led to the conclusion that there is a similar connection between the presence of soluble albumenoids and the activity of the solution of koji which seems to hold in the case of malt extract.

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