May 15. 1920 Influence of Fermentation on Starch in Silage 177 



throughout the fermentation period. Appreciable increases in alcohol 

 occurred up to the third month, finally reaching a concentration of 0.39 

 per cent. That there was no marked maximum production of alcohol 

 at any time was due probably at first to oxidation to acetic acid and 

 later to esterification. 



Sugar. — A maximum loss of sugar from the silage occurred by the 

 sixth day, when the sugar had dropped from 2.94 to 0.47 per cent. After 

 the eighth day the results were quite constant, indicating exhaustion of 

 sugar and the presence of reducing substances which were unfermentable 

 under the conditions existing in this silage. Unless the rate of fermenta- 

 tion equals the rate of formation of sugar no formation of sugar from 

 higher carbohydrates is indicated after the eighth day. 



Soluble starch and dextrins. — At no time were positive tests 

 obtained for these products in the silage juice. If they are transitional 

 in the decomposition of starch in the silage, they are so rapidly 

 changed to simpler decomposition products that they are never present 

 in reacting quantities even in green com. Only in cases of rapid gela- 

 tinization of relatively large quantities of starch would tests for these 

 constituents be positive in a medium like that existing in silage. Their 

 absence indicates that the insolubility of the silage starch is the limiting 

 factor in such a series of transitional changes in silage and that no exten- 

 sive hydrolysis of starch occurred. 



Microscopic examination of sections of kernels, leaves, and stems 

 showed no diflference in the appearance of the starch granules either 

 with or without stains. No change was discernible in the amount of 

 polarization and in the reaction of the granules with chloral hydrate 

 iodin, enzyms, acids, and alkalies as used by Reichert {12) in his chemi- 

 cal differentiation of the starches. 



Starch. — It would have been desirable to include determinations of 

 starch in the undried and fresh silage. Accurate methods for the starch 

 determination, however, require the sample to be in a fine state of divi- 

 sion, and such a condition could not be obtained without consequent 

 deterioration of the silage. It was also found that what actually hap- 

 pens when silage is being dried in a drying oven at 100° C. is not gelatini- 

 zation and hydrolysis Vv^ith the acids present, as would ordinarily occur 

 in water mixtures of starch at 100°, but rapid desiccation at a tempera- 

 ture below the gelatinization point of corn starch, which is above 65°. 

 The reason for this is apparent from the fact that the evaporating surface 

 is tremendous and the cooling effect due to vaporization is proportional 

 to the amount of water present. When the free water content ap- 

 proaches zero, then the gelatinization and hydrolytic tendencies of 

 starch also approach zero. The partially dried silage gave no positive 

 tests for soluble starch or erythrodextrin, and the sugar content was not 

 greater than that calculated from the determination of sugar in the juice 

 of the fresh silage. 



