CREAM RIPENING 77 



milk from this for ripening the second vat of cream; or 

 in case the second vat consists of partly soured hand 

 separator cream it would be best to churn this cream as 

 soon as possible after the addition of the buttermilk. 



PART III. ACID TESTS FOR MILK AND CREAM. 



Buttermakers who have had years of experience and 

 who rank high in the profession of buttermaking do not 

 find it safe to rely upon their noses in determining the 

 ripeness of cream for churning. They use in daily prac- 

 tice tests by which it is possible to determine the actual 

 amount of acid present. The method of using these tests 

 is based upon the simplest form of titration. 



Titration. This consists in neutralizing an acid with 

 an alkali in the presence of an indicator which determines 

 when the point of neutrality has been reached. 



Acids and alkalies are substances that have entirely 

 opposite chemical properties. The acid in milk gives it 

 its sour taste, and for our purpose, illustrates very well 

 what we mean by an acid. Ordinary lime may be used 

 to illustrate what we mean by an alkali. 



When lime is added to sour milk the acid unites with 

 the lime forming a neutral substance which is neither 

 alkaline nor acid. If we keep on adding lime to the milk 

 we reach a point at which all the acid has combined 

 with the lime. This is called the point of neutrality. The 

 moment this point is passed is made visible to the eye 

 by means of the indicator, (phenolphthalein) which is 

 colorless in the presence of an acid but pink in the 

 presence of an alkali. One drop of alkali added to milk 

 after the acid has been neutralized will turn it pink. 



