Figure 4 Curve showing the action of koji extract upon gelatinized starch at 410C

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Time in hours.

Time in hours.

The second set of experiments was conducted at the same temperature, different proportions of koji and starch being used. The amounts of koji and starch used for the following table were 5 grams of starch to 20 grams of koji.

Table 16: Action of Koji on Starch at 4-10°C

Time

Total starch in solution (koji deducted)

Specific rotatory power of starch

48 hours

4.638 grams

100.4°

164 hours

4.816 grams

75.3°

In this series the same specific rotatory power, 100.4° is attained in 68 hours, which it took 120 hours in the former series to arrive at, and the reduction is greater in the last series in 164 hours, than in 240 hours of the former. The reason of this lies in the larger proportion of koji used in the second than in the first series of experiments, but although four times as much koji was used, the rapidity of the action appears to be only about twice as great.

The third and fourth series of experiments were made at a temperature varying between 10° and 15°C, but otherwise they were conducted as before.

Table 17: Action of Koji on Starch at 10-15°C

Time

Total starch in solution (koji deducted)

Specific rotatory power of starch

1/2 hour

10.61 grams

172.8°

2 hours

10.45

158

21-1/2

10.56

131

26

10.65

120.4

46

10.51

110.5

Table 18: Action of Koji on Starch at 10-15°C

Time

Total starch in solution (koji deducted)

Specific rotatory power of starch

1 hour

9.705 grams

-

48 hours

9.925

121°

72 hours

9.925

113

Figure 5 represents the first of these results in the form of a curve. It will be noticed that although the two series of experiments at 10-15°C were made to all appearance under exactly the same conditions, yet the reduction in the specific rotatory power at a given time is much greater in the second series. This may be accounted for in one of two ways. It may be that different portions even of the same preparation of koji differ in activity, or it may be that, although the limits of temperature in both cases were the same, the average temperature of the former series was higher than of the second set. That this might affect the results will be seen by reference to Figure 5 in which the inclination of the curve between 21-1/2 hours and 26 hours is greater than the average. This was undoubtedly the result of the solution during that interval having a higher temperature than the average of the whole time. These limits fell in the middle of the day when the temperature was 15° the whole time; if an examination of the liquid had not been made at the two periods mentioned this sudden drop would not have been observed, but the average inclination from the beginning to 21-1/2 hours would have appeared slightly greater. In the same way if the temperature had remained during one set of experiments more nearly 15° and in the other more nearly 10° during the whole time, the action might be expected to be more rapid in the former than in the latter.

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