306 



Prof. R. W. Atkinson. 



determined. The rice contained 14*2 per cent, of water and the koji 

 29'5 per cent; thence 85*8 parts of the dried rice yielded 76*35 parts 

 of dry Jcoji, that is, 89 per cent., and thus a loss of weight occurs 

 amounting to 11 per cent, of the dry rice used. This loss consists 

 mainly of starch, which is oxidised to carbonic acid and water, and 

 corresponds to an oxidation of 4*9 per cent, carbon. More carbon, 

 therefore, undergoes oxidation than Day found in the case of germina- 

 ting barley,* which varied from 23 to 2' 6 per cent. 



As in one day about 107 lbs. of dry rice are converted into koji in 

 each chamber, the amount of carbonic acid formed will be 1 3 i -x5*24 = 

 19*2 lbs., and such a large quantity evolved in situations from which 

 it is difficult to remove it frequently leads to stoppage of the work for 

 some time. The only means adopted of effecting a change of air con- 

 sists of a square shaft about 8 inches in one direction and 6 inches in 

 the other, leading from the anterior end of the passage into the open 

 air above. It will be evident, therefore, that as the ventilation depends 

 upon the difference of temperature between the inner and the outer 

 air, it will be much better in winter than in summer. In fact, it is in 

 the spring and early summer that the stoppages occur, for, as the tem- 

 perature observations taken during May show-, the difference at that 

 period between the inner and outer air is not more than a few degrees. 

 Under such conditions the growth of the fungus must be much less 

 active, and perhaps this is one reason why the production of koji in the 

 summer is almost abandoned. 



II. — Action of Water on Koji. 



The koji prepared in the manner just described consists of grains of 

 rice bound together in lumps by the interlacing threads of mycelium. 

 A single grain separated from the rest presents a peculiar woolly 

 appearance on the surface, but does not appear to have increased very 

 much in bulk. Under the microscope, a section shows that the outer 

 cells are loose and penetrated by the fibres of the mycelium, whilst in the 

 centre of the grain the cells have a horny appearance, and the starch 

 granules cannot be distinguished. 



When the koji grains are allowed to remain in contact with water 

 for some time, a large proportion is dissolved by the water, which 

 then assumes a yellow colour. Very little of the koji remains except 

 the mycelial fibres and the skeleton of cellulose when the digestion is 

 made in warm water. The amount of matter brought into solution 

 varies according to the duration and the temperature of digestion. At 

 low temperatures, and after about fifteen or twenty minutes, from 

 12 to 15 per cent, of solid matter, calculated on the koji used, is found 

 in solution ; but if the digestion is allowed to go on at a higher tem- 

 perature, or for a longer time, from 30 to 60 per cent, will be dissolved. 

 * " Journ. Chem. Soc," Trans., 1880, pp. 651-657. 



