CONTROL OF CHEESE-MAKING. 441 



100 

 (i.) Ib. of cheese - {Solids not fat x 0-3 + (fat - 0-23 } X -^ . 



100 

 (ii.) Ib. of cheese- {aldehyde figure X 0-135 + (fat - 0'23) } X ^ . 



i no 



(iii.) Ib. of cheese = {curd by Lindet's method x (fat 0-23)} X -'. 



55 



These formulae give the weight of green cheese assumed to 

 contain 45 per cent, of water and salt, and apply fairly well to 

 such cheeses as Cheddar. Cheshire, and Stilton. 



The percentage of fat should be estimated in the whey, and 

 this should not exceed 0-3 ; a higher figure shows that the curd 

 has been cut too soon, or carelessly. 



The acidity of the milk, the whey, and the curd should be 

 determined ; the milk before renneting should have an acidity 

 of 22 to 24, the whey should be drawn at about the same acidity, 

 and the curd vatted when the acidity has reached about 100. 

 The acidity of the curd is best tested with a hot iron ; a small 

 piece of curd is placed on a hot iron, and withdrawn im- 

 mediately ; when the curd pulls out in strings it is ready for 

 vatting. 



The Fermentation Test for Milk. In order to ascertain the 

 fitness of milk for making good cheese, the appearance of the 

 curd on souring should be noted ; the test is carried out by 

 filling test-tubes, which must be scrupulously clean, and prefer- 

 ably sterilised, with milk, and after covering them, keeping them 

 for twelve hours at a temperature of 40 C. (104 F.), and exam- 

 ining the curd produced. A good milk will either not have 

 curdled in the time, or will have produced a homogeneous curd, 

 with the development of a clean acid smell. If there is much 

 separation of whey, if the curd is granular, or especially if the 

 curd contains many bubbles or is spongy, the milk will not 

 make good cheese ; a strong unpleasant smell is also very undesir- 

 able. All these conditions indicate the presence of undesirable 

 organisms ; to some- extent the effects of these may be counter- 

 acted by the addition of a starter (a pure cultivation of lactic 

 acid bacilli) before renneting, but a milk giving a very gassy 

 curd in the fermentation test will not produce good cheese. 



Other Products Derived from Milk. 



Commercial Milk-sugar Preparation. Where whey is a 

 bye-product, in cheese making countries, it is treated for the 

 manufacture of milk-sugar. This is done by allowing it to stand 

 so that the cream present may rise to the surface, heating it, 

 and removing the cream and a portion of the proteins. The 

 whey is neutralised with lime, and a little alum added, which 



