CHAPTER XXXII 



TESTS NECESSARY IN CREAMERIES 

 The butter fat test is nattirally the most important (Chapter 

 XXVIII, yet the proper conduct of any creamery includes sev- 

 eral others as well (Fig. 121). 



The acid test is a method of determining the quantity of 

 acid in or degree of sourness of a cream by the use of an alkali 

 solution. This is made by dissolving 4 grams of caustic 

 (KOH) in 1000 c.c. pure water. This is a simple titration of 

 an alkali solution of known strength against a known amount 

 of sour cream of unknown acid streng-th in the presence of 

 phenolphthalein as an indicator, two or three drops being used. 

 So long as the mixture of cream and alkali solution remains 

 white the acid is in excess. When the acid is killed the whole 

 mixture turns pink. If 17.6 c.c. of cream be taken as sample a 

 normal acidity would require the use of about 12 c.c. of the alkali 

 solution, which would indicate the presence of about 0.61 per 

 cent acid. The formula usually employed in the determination 

 of acid is that devised by Dr. Manns : 



c.c. alkali X. 009 ^, ,-„ , , ., 



z ,- X 100 = per cent of aoid. 



c.c. sample used 



The lime water test for acid is cheaper and easier of opera- 

 tion than the Manns and sufficiently accurate when used on sour 

 creams. The lime water is made by putting a quantity of quick 

 or air-slacked lime in any convenient jar, covering with water, 

 stirring and letting stand for sixty hours or more in order that 

 the water shall have taken up all the lime possible. When the 

 solution has reached its condition of constant strength the clear 

 liquid should be poured or dravra off into a separate bottle and 

 more water added to the lime and stirred for a later usage. To 

 make tie test IY.6 c.c. of sour cream are then measured into a 



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