58 PROVISIONAL METHODS FOR ANALYSIS OF FOODS. 



Lenz. a Although useful, the results are not of as great value as those by the dias- 

 tase method. 



13. DETERMINATION OF STARCH BY DIASTASE METHOD. b 



Extract 4 grams of the finely pulverized material with ether and 10 per cent 

 alcohol, as described in the preceding section. Carefully wash the wet residue from 

 the paper into a beaker with 100 cc of water, heat on an asbestos plate to boiling 

 with constant stirring, and continue the boiling and stirring thirty minutes. Replace 

 the water lost by evaporation, and immerse the beaker in a water bath kept at from 

 55 to 60. When the liquid has cooled to the temperature of the bath, add 10 cc of 

 fresh extract of malt (prepared by digesting for two or three hours 100 grams of 

 p,>wdered fresh malt with 1,000 cc of water and filtering), and digest the mixture 

 for one hour, with occasional stirring. Boil a second time for fifteen minutes, cool, 

 and digest as before with another 10-cc portion of malt extract. Heat to boiling the 

 third time, cool, and make up the liquid to 250 cc in a graduated flask, filter 

 through a dry paper, and remove 200 cc of the filtrate to a 500-cc flask. Conduct 

 the inversion with acid, and determine the reducing power of the solution, as already 

 described under "Copper-reducing matters by direct inversion," making a correction 

 for the copper reduced by the added malt extract, as determined by blank analyses. 

 The residue after the malt digestion, when examined microscopically, must be 

 entirely free from starch. 



Results by Winton, Ogden, and Mitchell c show that cayenne pepper, mustard, 

 and certain other materials, which are practically free from starch, yield very little 

 or no copper-reducing matter, when treated by the method just described. This 

 treatment is, therefore, without effect on the cellulose, pentosans, or other matters in 

 the spices named, although they yield copper-reducing material on treatment with 

 acid. 



On the other hand, in decorticated white pepper and Jamaica ginger, which con- 

 tain little besides starch that is affected by acid, practically the same results are 

 obtained by the diastase method as by direct inversion with acids. 



This determination of starch is very valuable as a means of detecting starchy 

 adulterants in spices normally free from starch and nonstarchy adulterants in spices 

 which contain starch. 



14. DETERMINATION OF CRUDE FIBER. d 



The method is that adopted by the Association of Official Agricultural Chemists 

 for the analysis of cattle foods, except that the fiber is filtered and weighed on a 

 paper rather than on a Gooch crucible, since the latter is liable to clog, rendering 

 filtration impossible. Place the residue from the determination of ether extract in 

 a 500-cc Erlenmeyer flask, and add 200 cc of boiling 1.25 per cent sulphuric acid. 

 Loosely cover the flask, heat at once to gentle boiling, and continue the boiling 

 thirty minutes. Filter on a paper, wash with hot water, and rinse back into the 

 same flask with 200 cc of boiling 1.25 per cent sodium hydroxid solution, nearly 

 free from carbonate. After boiling, as before, for thirty minutes, collect the fiber 

 on a weighed paper, thoroughly wash with hot water, and finally with a little alco- 

 hol and ether. Dry to constant weight at 100 C., and weigh. Deduct the amount 

 of ash in the fiber, as determined by incineration, from the total weight. 



Determine the loss in weight sustained by the paper on treatment with sodium- 

 hydroxid solution, alcohol and ether, and introduce the necessary correction. 



Ztschr. anal. Chem., 1884, 23, 501. 



'Maercker, Handbuch der Spiritusfabrikation, 7th ed., 1898, p. 109; Wiley, Principles and Practice 

 of Agricultural Analysis, 1898, Vol. Ill, p. 198. 

 Conn. Agr. Expt. Sta. Kept., 1898, p. 189. 

 d See Appendix, pp. 154 and 155. 



