43 



stick together. (8) The curd should show strings one-eighth of an 

 inch long on the hot iron by the test described in Lecture 5, paragraph 

 5. (4) Instead of the hot-iron test the amount of acid in the whey may 

 be used, which should be about 0.01 per cent less than at the time of 

 setting. Thus, if the acidity of the milk was 0.19 per cent at the time 

 of setting, the acidity of the whey should be about 0.18 per cent when 

 the whey is removed from the curd. 



3. Changes caused in curd hy formation of acid. — (Reference book 

 No. 13, p. 36.) The curd formed by rennet from milk is an impure 

 form of calcium (lime) paracasein. When lactic acid is formed in the 

 curd and whey it gradually unites with the calcium, forming free (not 

 combined with calcium) paracasein and calcium lactate. It is this 

 free paracasein that draws out in silky threads on a hot iron. It is 

 free paracasein also that imparts to cheese curd its peculiar plastic or 

 "matting" properties. The formation of free paracasein is the main 

 object of forming acid in cheese making. 



4. Effect of excessive and incomplete heatirig i^^coohing"). — A curd 

 that is heated too high or too long produces a cheese with too little 

 moisture, resulting in a "corky" texture. Heating at too low a tem- 

 perature or for an insufiicient length of time results in producing 

 cheese containing too much moisture and showing a pasty, soft body. 

 Such cheese sours easily. 



5. Cheddaring the curd. — This operation is the distinctive feature of 

 the cheddar method of cheese making. It consists, essentially, in 

 allowing the curd to mat or pack together in solid chunks after removal 

 of whey. The operation may take place (1) directly on the bottom of 

 the vat or (2) on curd racks placed in the bottom of the vat, or (3) it 

 may be removed to a curd sink (reference No. 3, p. 74, or No. 8, 

 p. 67). 



6. Matting curd on vat bottom. — After the whey is drawn off the 

 curd is piled up along the two sides of the vat with an open channel 

 between to facilitate the running off of the whey that drains from the 

 curd. Wh.en pieces of curd have matted together, forming a solid 

 mass, it is cut into blocks about 8 by 8 by 1 2 inches, which are turned 

 over. After some draining the blocks are piled two deep, each time 

 the upper part being turned down. Later the blocks are piled in 

 deeper piles. The repiling is repeated again and again, always expos- 

 ing to the air the portions that were turned inside on the previous 

 piling in order to keep the heat uniform through the mass (refer- 

 ences No. 3, p. 74, and No. 8, p. 64). Curd racks and curd sinks are 

 frequently convenient in facilitating draining (references No. 3, p. 

 75, and No. 8, p. 64). 



7. Effects of cheddaring curd. — Cheddaring curd eifects two results: 

 Expulsion and draining of whey from curd, and (2) formation of free 

 paracasein as a result of the union of lactic acid with the calcium 



