374 BACTERIOLOGICAL ANALYSES 



Total Solids Determination. 



(1) Use .3000 gram sample. Add 2 c.c. distilled water to 

 the sample in this dish. Mix milk powder and water thoroughly 

 with the blunt rod. 



(2) Continue the determination as under evaporated milk, 

 but continue heating in the vacuum oven for twenty minutes. 



CHAPTER XXXII. 

 BACTERIOLOGICAL ANALYSES. 



While it is obviously beyond the scope and purpose of this 

 volume to discuss in detail the technique of bacteriological 

 analyses and microscopic preparations of the milk products de- 

 scribed herein, it is deemed advisable to offer some suggestions 

 that may serve for guidance of those who are not familiar with 

 bacterial fermentations in condensed milk. 



Sampling. Take samples of all products contained in open 

 receptacles, such as fluid milk, plain condensed bulk milk, barreled 

 sweetened condensed milk and milk powder, in sterile, cotton 

 plugged test tubes, or in small sterile glass-stoppered bottles, 

 and keep them in a cool place, preferably not above 35 degrees 

 F. until ready to use. Keep canned condensed milk sealed in 

 the original package until ready to use. If already open, invert 

 a petri dish or a beaker over the can to avoid contamination 

 from the air. 



Dilution for Numerical Counts. Make dilutions in 250 c.c. 

 glass-stoppered flasks. Before opening sealed cans, thoroughly 

 wipe off the entire top with a sterile piece of cheese cloth soaked 

 in a saturated solution of mercuric bichloride or a 5 per cent 

 solution of carbolic acid and flame the top of the can. Open 

 evaporated milk cans by punching a hole into their top, large 

 enough to insert the discharge end of a graduated pipette. Open 

 sweetened condensed milk cans with a sterile knife or a sterile 

 can opener. 



In the case of fluid milk and evaporated milk, measure with 

 a sterile graduated pipette two cubic centimeters of the product 

 and 198 cubic centimeters of sterile water into the 250 c.c. flask. 

 In the case of plain condensed bulk milk, sweetened condensed 



