May 15. 1920 Influence of Fermentation on Starch in Silage 1 75 



Starch. — After much preliminary work it was found that even by 

 grinding the undried silage in the best grinder available for the purpose 

 a degree of fineness could not be obtained which would give as high 

 results as those secured by drying the silage and then reducing it with 

 a Merker mill till it would pass through a 30-mesh sieve. It was also 

 found that the polarimetric method of Lintner as modified by Porst and 

 Crown (11) gave dependable and highly accurate results. 



Five gm. of the powdered silage prepared from the residue of the 

 moisture determination were mixed with 20 cc. of water in a mortar and 

 cooled in ice water. To this there were added 40 cc. concentrated hydro- 

 chloric acid previously cooled. The mixture was kept at 20° C. for one- 

 half hour. The contents of the mortar were then transferred to a 200-cc. 

 graduated flask with hydrochloric acid of specific gravity 1.125, and 8 cc. 

 of 4 per cent phosphotungstic acid were added. At this point it was 

 found necessary to add charcoal (norite) decolorizer. The mixture in 

 the flask was made up to the mark at 20° with hydrochloric acid of spe- 

 cific gravity i . 1 25 and kept at 20° for one-half hour. It was then filtered 

 and exactly 15 minutes after filtering (i hour and 15 minutes after the 

 addition of the 40 cc. concentrated acid) the reading was taken at 20*^. 

 From the rotation of 5 gm. pure starch the percentage of starch in the 

 silage was calculated. 



Corrections for the zero reading and for optically active substances other 

 than starch were made as follows : A 5-gm. sample was placed in a 200-cc. 

 graduated flask; 100 cc. of 50 per cent alcohol were added; and the whole 

 was boiled for one hour on the steam bath, then cooled and made up to 

 volume with 95 per cent alcohol, mixed and filtered. A loo-cc. portion 

 of the filtrate was evaporated almost to dryness, diluted to about 20 cc. 

 with water, and cooled. The modified Lintner procedure was then 

 followed as outlined above. 



Qualitative tests. — (/) For soluble starch the test was made by 

 applying the ordinary starch test with iodin to the centrifuged and 

 filtered juice. (2) The dextrin test consisted in adding a sufficient 

 amount of warm saturated solution of barium hydroxid to produce a 

 flocculent precipitate, quickly cooling and filtering, then precipitating 

 the barium in the filtrate with carbon dioxid, refiltering, and adding a 

 slight excess of hydrochloric acid and dilute iodin solution. The pres- 

 ence of dextrins was shown by a red coloration above that of the iodin 



solution. 



EXPERIMENTAL RESULTS 



The results were all calculated to the wet basis of the original silage. 

 No correction is made for the specific gravity of the silage juice, since for 

 all practical purposes this error is entirely negligible. 



The data for acidity, alcohol, and sugar given in Table I are similar 

 to data obtained by others. A discussion of these is not an object of 

 164178°— 20 4 



