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Chapter 6. Preparation of Moto
The process of preparing sake followed in the large breweries of Itami and Nishinomiya is very nearly the same, and may be easily divided into distinct periods, but sake is also very frequently prepared in much smaller establishments, in which case, properly speaking, only two divisions can be noticed, viz. the preparation of moto, and the principal process. The chemical changes which occur will be very easily understood after the details which have been given in the preceding part, but it will not be found possible to make a distinct separation between the solution of the starch and the actual fermentation as can be done in beer brewing. In that industry the starch is converted into sugar and dextrin during the operation of mashing, after which the diastase is destroyed by boiling before the fermentation is allowed to begin, but in the manufacture of sake these two processes go on at the same time, except during the first few days. In this respect, therefore, the brewing of sake differs from that of beer, and it may, perhaps, be one of the reasons why the former liquid is so much more alcoholic than the latter.
As carried out at Itami and Nishinomiya sake brewing consists of the following series of processes:
- Preparation of moto
- Preparation of soye
- Preparation of naka
- Preparation of shimai
- Filtration and clarification
Of these that which requires most care and is most liable to fail is the first, the preparation of moto.
MOTO
In the preparation of moto steamed rice, koji, and water are used in proportions which differ slightly in different works. The term moto is used to express not only the product of this operation, but also a definite amount-thus the workmen speak of one moto, two and a half moto, and so on. At Itami, the most famous district, the proportions for moto are:
It may be remarked that the numbers indicating the mount of steamed rice and koji used refer, not to the finished products, but to the quantity of rice taken to form them.
At Nishinomiya, another very celebrated sake making district, the proportions are as follow:
At a brewery in Tokyo at which I had the opportunity of watching the whole process from beginning to end and of making analyses of the mash at different periods, the proportions for one moto were:
To find the percentages of dry rice and water in the last mixture we proceed as follows. The weight of one koku of water is 48 kuwamme (B.S. Lyman, Geological Survey. Report. Progress. 1878-79) and we have already seen that the weight of one koku of rice is on the average 40 kuwamme, hence the weight of one moto is:
After steaming, the rice used was found to contain 38.8% water, hence the original rice, which contained 14% water had taken up in addition 40% of its weight in water. 16 kuwamme of rice will thus take up 6.4 kw. of water, which, together with the 14% already present, will give 6.4 + 2.24 = 8.64 kw. of water and 13.76 kw. of dry rice.
By the conversion of rice into koji 100 parts of common rice form 108 parts of koji containing 30% water, thus 6.4 kw. of rice will form 6.9 kw. of koji, containing 4.83 kw. dry rice and 2.07 kw. of water.
The total dry rice, therefore, is 13.76 + 4.83 = 18.59 kw.
The water taken up is 8.64 + 2.07 = 10.71
The water subsequently added is 19.2, added to the 10.71 gives 29.91 kw., or in -percentages:
The quantity taken for 1 moto is mixed and divided into six equal parts, each of which is placed in a shallow wooden tub called hangiri, of a capacity of 0.267 koku. The mass is thoroughly mixed by hand for two hours, any lumps which are formed being broken down. At first the mixture of rice, koji, and water is so thick that it would hardly fall out if the vessels were inverted, but in a short time it loses its stiffness and becomes thin. After 24 hours have elapsed stirring with paddles (kai) begins, and when this is finished the whole is thrown into a larger tub (moto-oroshi), provided with a cover cut in two to facilitate the inspection of its contents, and covered with matting for the purpose of diminishing loss of heat as much as possible. The preceding operations have been carried on at a low temperature, from 0°C to 9 or 10°C at the highest, and the chemical change which occurs during this period will be easily understood from the account already given of the action of koji upon gelatinized starch. The rice grains having been steamed are of course in the gelatinized state, but, owing to the greater compactness of the grain, the action is much less rapid than in the experiment carried out at 4 to 10°C as described earlier. Doubtless the mixture at first contains a certain proportion of maltose, as well as dextrose and dextrin, but it will be gradually changed into dextrose. The duration of this simple digestion in the cold differs in the different works and even in the same place. At Nishinomiya, an interval of one day after transference into one vessel is allowed before the mixture is warmed; at Itami it is sometimes heated at once, and sometimes kept for five or six days. At the Tokyo brewery, the mash was heated at 3 p.m. on the fifth day after mixing, and the two following analyses show its composition before that event took place.
The effect thus far has been to increase the amount of dextrose at the expense of the starch; at the same time a fresh proportion of dextrin is no doubt formed, but this increase is obscured by the fact that there are two actions going on, formation of dextrin by a splitting up of the starch, and a disappearance of dextrin by the hydrating action of the koji, and the result of these two actions is to leave the dextrin very nearly what it was on the third day. It is important to observe that even so early as the third day only dextrose, and no maltose, is present in solution; the observed specific rotatory power is 124°, and that calculated for dextrose and dextrin in the observed proportions is 123.4°. The specific gravity of the mash has increased a little owing to the larger amount of solid matter in the solution, and the specific rotatory power has diminished, the proportion of dextrose to dextrin being greater on the fifth day than on the third day. The composition of the mash as given on the fifth day may probably be looked upon as the usual composition just before heating; this sample was taken at 8 a.m. and the heating commenced at 3 p.m. on the same day. If no change had occurred the mash would have contained 32.17% starch. The dextrose and dextrin on the third day correspond to 11.735, which leaves 20.43% of starch undissolved, and in the same way the starch undissolved on the fifth day amounts to 15.46%.
The heating is effected in all establishments in the same way. A closed tub called kumume or daki of a somewhat conical form, 18 inches high, 12 inches at its upper diameter and 9 to 10 inches in diameter at the lower part, is filled with boiling water and tightly closed. It is supported by means of a handle formed by a cross bar fastened to two ears which project upwards from opposite sides; in this way it is let down into the thick mash contained in the large tub, and the mixture is agitated by moving the heater about. As a rule one heater is allowed to remain in the mash for a half a day, and is then replaced by a fresh one which is left in for the same time, but the number of heaters used depends to some extent upon the temperature of the air. During the 13 days required for the completion of the moto at Itami from 5 to 9 heaters are employed, and at Nishinomiya from 10 to 13 are used in the same time. It is found undesirable to raise the temperature of the mash too rapidly, probably because a too high temperature at first would allow the acid ferments to become developed to the exclusion of the alcoholic ferments.
In the Tokyo brewery the heaters were allowed to remain in the mash for a much shorter time. Introduced on the fifth day at 3 p.m. the liquid was transferred back from the large tub into the shallow pans on the eighth day at 7 a.m. and was allowed to cool as much as possible until the fourteenth day at 11 a.m. when a fresh addition of rice and koji was made, the commencement of the main process.
The heating of the mash has the effect of inducing alcoholic fermentation to set in with great vigor. On the seventh day, when the next sample was taken, gas was rising rapidly through the mash and on coming to the surface burst with a slight, explosive noise. At the same time a very strong, sharp odor was perceptible, whilst a foam covered the surface. The following analyses (Table 23) give the composition of the moto from the seventh to the fourteenth day, after which the main process began. The mash was again placed in the shallow hangiri at 7 a.m. on the 8th day.
The alcoholic fermentation set in somewhat rapidly, for between 3 p.m. on the fifth day and 8 a.m. on the seventh day 5% of alcohol was formed, and the dextrose diminished from 12.25% to 5.4%. The amount of dextrin increased in that time, but the increase is probably only apparent, caused by the loss of matter in the form of carbonic acid. The solution of starch during this stage does not appear to have gone on very actively; there is a discrepancy in the numbers calculated on the seventh to the fourteenth days, which probably arises from the difficulty of taking an average sample of the mash. The percentages given are calculated on the original weight of the mash.
From the seventh to the fourteenth day the alcohol steadily increases; the dextrose is very quickly removed, there being less than 1% on the tenth day, and between the seventh and the tenth the dextrin is reduced from 7% to 2.8% about which it remains during the rest of the time, owing probably to the koji having lost its activity.
When the liquid was heated by the introduction of hot water barrels the temperature attained was 23° in the Tokyo brewery, and 25°C at Nishinomiya. As soon as the mash was transferred to the shallow tubs, however, it began to cool down, the activity of the fermentation not being sufficient to keep up the temperature; the composition of the liquid indeed, shows that this result must follow inasmuch as there is not enough food left in the liquid in the form of sugar and dextrin to allow the active growth of the ferment to continue. Hence on the tenth day the temperature fell to 14°C, on the twelfth day to 10°C and on the fourteenth day to 9°C.
A sample of the finished moto obtained from the brewery at Nishinomiya had the following composition, which agrees very well with that obtained in Tokyo, from which it may be inferred that different specimens of moto will not differ in composition to any marked extent.
Finished Moto from Nishinomiya
The chemical changes which go on in the production of moto are sufficiently easily explained in general terms. During the first days, whilst the mixture is kept at a low temperature, the koji is acted upon by the water and the solution then attacks the starch according to the reactions already indicated. This results in the production of a saccharine and dextrinous liquid forming a suitable food for the ferment which subsequently establishes itself in the liquid on warming. How the ferment appears will be discussed in a later section. Whilst the yeast is growing and converting the sugar into alcohol, the solution of starch and the hydration of dextrin by the koji still continue so long as the latter retains its activity, but that appears to be destroyed some time before the moto is completely finished. At the end of this stage the yeast ferment though not vigorous, is well formed and only requires a fresh addition of food to commence growing with renewed activity. It may, indeed, be said that the preparation of moto has for its main object the production of a healthy ferment, so that the use of the moto in the subsequent operations answers very nearly to the yeast added to the wort in beer brewing.
The sake brewer judges of the progress of the moto by the vigor of the fermentation and by the taste of the liquid. At Itami it is said to require 13 days to obtain the proper taste; after three days the taste is sweet owing to the presence of much dextrose; after six days it is astringent, on the seventh day is slightly alcoholic, and finally, it becomes sour. When finished the brewer is able to distinguish five tastes, respectively sweet, sour, bitter, astringent, and alcoholic, and of these the sour, bitter, and astringent are most pronounced. The formation of the acid is also formed during the time the mash is allowed to cool in the shallow vessels, although its amount cannot be very large seeing the great development which the yeast has taken. The bitter and astringent tastes are due to the presence of the yeast, though the nature of the substances giving rise to them is unknown.
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