EXPERIMENT STATION BULLETINS. 535 



c.c. of Sc'liardiiigers solution (190 c.c. of distilled water, 5 c.c. formalin 

 and 5 c.c. of saturated alcoholic methylene blue) to 10 c.c. of the medium 

 to be tested, the reagent and milk were shaken to mix uniformly and 

 placed in a waterbath at 37° C. for half an hour. Decolorization of the 

 methylene is recorded as reductase positive. 



Moisture. The moisture was determined by heating 10 gms. of butter 

 in an aluminum cup according to the Ames test. The sample was re- 

 weighed and the percent of moisture obtained by multiplying the loss in 

 weight by 10. 



fialt. The amount of salt was determined by a slight modification of 

 the Shaw test, the silver nitrate reagent is of such strength that 1 c.c. 

 represent 0.001 grm. of salt or 0.1 percent Avhen a 1 gm. sample is used, 

 potassium chromate is used as an indicator. 



Acidity. This determination Avas made by diluting 10 c.c. of the sam- 

 ple with distilled water and titrating with N/IO NaOH (the samples of 

 butter were dissolved in a mixture of equal parts of alcohol and ether 

 and not diluted with distilled water (See 10, p. 12) and recorded as 

 cubic centimeters of N/10 acid per 100 grms. 



Fat. The percent of fat present Avas determined by the Babcock test. 



Spores of anaerohic gas producers. The presence of spores of anaero- 

 bic gas-producers was tested for in every step of butter manufacture in 

 the following way: the medium to be examined was placed in sterile 

 test tubes ; 1 c.c. in the first, 1 c.c. in the second, 8 c.c. in the third and 

 12 c.c. in the fourth tube. Enough sterile milk was added to the first 

 three tubes to make the contents of each approximately 1% c.c. The 

 tubes were heated in a water bath at 80° C. for ten minutes, cooled and 

 the medium covered with one-half to three quarters of an inch of sterile 

 liquid paraffin to exclude the air. The tubes were incubated at 37° C. 

 for two days. An abundant production of gas, the cream being disturbed 

 and often thrown to the surface of the paraffin oil and coagulated masses 

 of casein Avere recorded positive for spores of this group. 



Coli-aerogenes group. The presence of this group was determined by 

 the iuA'erted vial method, 1 c.c, 0.5 c.c, dilutions of 1 :10, 1 :100, and 

 1 :1,000 of the sample was used. The production of gas in dextrose broth 

 Avas considered positive. No attempt Avas made in this Avork to deter- 

 mine the presence of yeasts. 



Peptonizers. To determine the number of peptonizing microorgan- 

 isms (colonies), the casein agar plates, after counts Avere recorded, were 

 flooded Avith N/10 lactic acid. The action of the lactic acid is to precip- 

 itate the dissolved casein Avhich produces an opaque, white medium with 

 the exception of a clear zone around the colonies which have hydrolyzed 

 the casein. Colonies surrounded by a clear zone and thus set off from 

 the rest of the solid Avhite medium are considered peptonizers. 



Acid Organisms. The lactic acid bacteria AA^ere determined by direct 

 count on litmus lactose agar plates. Tliey form either a distinct boat- 

 shaped or a round colony Avliich is small and of a distinct pinkish-red 

 color. This does not include members of the coli-aerogenes or of the bul- 

 garicum group. No attempt Avas made to determine the numbers of 

 Bact. hiilgaricum present in cream or butter. 



Inert and Indifferent Organisms. Every microorganism that made a 

 visible colony on either the litmus lactose agar or the casein agar and 

 that was not counted as a gas-producer, as a peptonizer or as an acid- 

 producer is grouped under this head. 



