The Principal Process

In the chief fermentation process as carried out at Itami and Nishinomiya there are three stages, called respectively soye, naka, and shimai, although they do not differ from one another in any essential particular. In the Tokyo brewery it is not so easy to distinguish these stages, and it will, therefore, be most convenient to describe the former methods first, reserving the latter and the analyses of the product at different times until the others have been disposed of.

At Itami the proportions used to one moto are the following:

Moto 1.30 koku

Steamed rice 1.30 koku

Koji 0.35 koku

Water 1.30 koku

4.25 koku

At Nishinomiya the following quantities are used:

Moto 1.33 koku

Steamed rice 1.05 koku Koji 0.35 koku

Water 1.15 koku

3.88 koku

This mixture is placed in a large tun called sanjaku-oke (or three-foot tub) which holds about 8 koku, and which is therefore, only about half filled. The mixture is stirred every two hours, and, after 42 hours at Itami and 3 days Nishinomiya, the first stage (soye) is finished, and the product is divided into two parts preparatory to the second stage. During this period fermentation sets in and the temperature rises, that of one batch examined at Itami being 20°C the temperature of the air at the same time being 11°C. An odor, strong, pungent, and fragrant arose from the mash. A sample of the mash from Nishinomiya had the following composition.

Alcohol

11.0%

Dextrose

0.18%

Total acid

0.36%

Starch

17.52%

29.06%

The amount of dextrose present is very small, a fact which is probably accounted for by the continuous growth of the ferment between the time when the sample was taken and the time of its analysis. The alcohol on that account is doubtless higher than in the mash at the end of this stage.

As soon as the first stage is finished the mash is divided into two parts each of which is placed in a three-foot tub, and a fresh amount of steamed rice, koji, and water added in the following proportions, using the whole of the soye.

At Itami they use:

Soye 4.25 koku

Steamed rice 2.00 koku Koji 0.65 koku

Water 3.00 koku

9.90 koku

At Nishinomiya, the following mixture is made:

Soye

Steamed rice

Koji

Water

3.88 koku 1.80 koku 0.60 koku 2.40 koku

8.68 koku

The stirring is continued every two hours as in the soye stage so that the grains of rice may not fall to the bottom, and get beyond the action of koji. The mixture is left for 24 hours by which time the naka stage is finished. At Itami the temperature observed was lower than in the soye stage, but the observation was made soon after mixing so that the fermentation had not then had time to fully develop itself; the temperature observed was 15°C that of the air being 11°C. This mash also possessed a pungent, fragrant odor though not so powerful as in the case of the soye.

After the lapse of 24 hours, that is at the end of the second (naka) stage, the quantity of material in each tub is again divided into two, so that each of these parts now contains only one-fourth of the original moto. To the whole a fresh admixture of steamed rice, koji, and water is made—at Itami in the following proportions:

Naka

Steamed rice

Koji

Water

9.90 koku 3.30 koku 1.00 koku 4.20 koku

18.40 koku

At Nishinomiya, the following proportions are used:

Naka

Steamed rice

Koji

Water

8.68 koku 3.60 koku 1.20 koku 6.20 koku

19.68 koku

The quantity of water added at this stage (shimai) depends on the alcoholic strength required. At first the whole quantity is divided amongst four tubs, but after standing for about 3 days the mixture is collected by degrees into one large tub called roku-shaku-oke, holding about 24 or 25 koku. In this the fermentation goes on more vigorously for two or three days after which it gradually ceases—the froth sinks, and the liquid is now strongly alcoholic and ready for filtration. The time during which it is allowed to stand before filtration varies, but is not a matter of much importance.

It may be useful to collect together the amounts of each material used:

Table 24: Itami

Stages

Rice for steaming

Rice for koji

Water

Moto

0.5 koku

0.2 koku

0.6 koku

Soye

1.3 koku

0.35 koku

1.8 koku

Naka

2.0 koku

0.65 koku

3.0 koku

Shimai

8.3 koku

1.0 koku

4.2 koku

7.1 koku

2.2 koku

9.1 koku

284 kuwamme

88 kuwamme

436.8 kuwamme

284 kuwamme of rice contain 244.24 kuwamme of dry rice and 39.76 kw. of water. It also takes up in addition, by steaming, 113.6 kw. of water—hence the total weight of water is 153.36 kw.

88 kuwamme of rice after being converted into koji weigh 95.04 kw. and the koji contains 66.53 kw. of dry rice and 28.51 kw. of water.

We have, therefore:

Dry rice Water

Steamed rice 244.24 kw. 153.36 kw. Koji 66.53 kw. 28.51 kw.

or in percentages:

Dry rice 32.3 % (containing 27.13 starch)

100%

We may now consider the method of brewing followed in Tokyo. One feature is that the frequent subdivision of the mash does not take place as in Itami and Nishinomiya, but after the moto has been finished, it is transferred to a large tub (rokushaku oke) and the subsequent additions are made to it in the same vessel. This must result in a saving both of material and of labor, and at the same time the temperature required for the active growth of the ferment is better maintained as will be seen from the observations which will be recorded presently.

In the description of the preparation of moto the last analysis given of the mash was at 8 a.m. on the fourteenth day. The next sample was taken at 8 a.m. on the seventeenth day, when the main process was already entered upon. To the quantity of material one moto the following amounts of rice and koji were added at 11 a.m. on the fourteenth day.

Steamed rice 1.0 koku Koji 0.3 koku

Water 1.2 koku

Moto 0.96 koku

3.46 koku

A second addition was made at 11 a.m. on the sixteenth day, amounting to:

Steamed rice 1.2 koku Koji 0.36 koku

Water 1.44 koku

Already mixed 3.46 koku 6.46 koku

Supposing that no alteration had taken place in the mixture, the quantities of dry rice and water present in the mash, including the first addition, would be:

Dry rice 34.9 % (containing 29.32 starch)

100%

A sample of the mash taken on the seventeenth day from the commencement had the following composition:

Dextrose 2.06 %

Dextrin 3.890 %

Glycerin, albumenoids etc. 0.043 %

Fixed acid 0.015%

Water 88.192%

Undissolved starch & cellulose 12.814 %

Specific rotatory power 160°

Specific gravity of mash 1.03

Temperature of mash 19°C

The specific rotatory power of the solution is as high as 160° because the percentage of dextrin in the solid matter is so large, amounting to 65% of the total solid matter in solution. The number calculated for the following is 160.7°.

Dextrin 65.00

Dextrose 34.36

Inactive matter 0.64

Hence, at this stage also no maltose is present in solution, that first formed having been converted into dextrose.

The two additions of steamed rice, koji, and water on the fourteenth and sixteenth days, respectively, may perhaps be regarded as indicating the division of the main process into the stages soye and naka. If this be so the third addition which is made on the eighteenth day at noon will correspond with the commencement of the stage called shimai at Itami and Nishinomiya. The last addition consisted of:

Rice 1.40 koku

Koji 0.42 koku

Water 1.68 koku

Already present 6.46 koku 9.96 koku

The weights and percentages of dry rice and water present, if no change had taken place, would be:

Weight Percentage

The temperature of the mash at this stage rises considerably owing to the very active growth of the alcoholic ferment; thus on the seventeenth day the temperature rose to 19°C, on the nineteenth day to 25°C, and on the twenty-first day to 26°C, by which time the fermentation was for the most part finished, and the temperature then fell to 20°C on the twenty-fourth day and to 12°C on the twenty-eighth day. During this time the temperature of the air was never above 12°C and, for most of the time, far below that point. The composition of the mash during this the last stage of the main process will be seen from the accompanying analyses.

Table 25: Composition of mash during principal process

Day 19

Day 21

Day 24

Day 28

Alcohol

9.44%

11.83%

12.41%

13.28%

Dextrose

1.16

0.27

0.27

-0-

Dextrin

2.74

1.42

0.47

0.41

Glycerin, albumenoids, etc.

1.09

1.98

1.68

1.99

Fixed acid

0.08

0.058

0.086

0.107

Volatile acid

0.029

0.086

0.061

Water

85.54

84.413

84.998

84.202

100

100

100

100

Specific rotatory power

132.8°

88.8°

48.2°

36°

Specific gravity of mash

1.017

0.994

0.990

0.988

Temperature of mash

25°C

26°C

20°C

12°C

Undissolved starch

7.85%

5.534%

5.40%

4.18%

A glance at the numbers given in this table will show how far the fermentation has been carried. After the addition made on the eighteenth day, the mash was left to itself except for the stirring which was continued as before about every two hours. During this time a vigorous growth of ferment went on, gas escaped rapidly, and a pungent odor was spread throughout the chamber. On the nineteenth day the effervescence was very strong, and it rose to a maximum between that day and the twenty-first day when, although the temperature was higher, the amount of effervescence was perceptibly less. The taste of the mash was bitter and strongly alcoholic. On the twenty-fourth day the effervescence was very slight and the odor was strongly ethereal, but although the effervescence had diminished greatly, formation of alcohol still went on, as between the twenty-fourth and twenty-eighth days the percentage increased from 12.41% to 13.23%. How much further the process might have been carried is doubtful; at this time the undissolved matter was separated from the alcoholic solution and analyses could not be continued, but from the analysis of the mixture on the twenty-eighth day compared with that on the twenty-fourth day it appears that the diastase of the koji was not yet destroyed. The amount of dextrose and dextrin which disappeared during that interval was not sufficient to account for the increase in the amount of alcohol, which must therefore, have been formed by the solution of a fresh quantity of starch.

From the numbers giving the percentage of undissolved starch it will be seen that it suffers a constant diminution, a change which shows that the solution of the starch under the influence of the koji is a continuous process, going on concurrently with the fermentation of the sugar formed. Indeed, it would appear that the conversion of the sugar into alcohol is a more rapid process than the production of sugar from starch, if it were otherwise, we might expect the sugar to increase at first, or at any rate, to remain more nearly constant than it does.

A point of interest is the increase in the amount of fixed acid from the nineteenth day onwards. The numbers given are calculated for sulfuric acid, although the acid present is for the most part succinic acid, but even in the last analysis its amount is much less than was found during the preparation of moto. In that stage, however, owing to the greater surface exposed to the air, and the lower activity of the alcoholic fermentation, other organisms are present, lactic acid ferments especially, and these contribute to the larger amount of fixed acid in the moto.

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