[HARRISON] DISTRIBUTION OF BACTERIA IN CANADIAN CHEESE 8S 



its flaky consistency and the development of .7 to .85 per cent of acid in 

 the whey which drains from the curd. The curd is then put through a 

 mill which cuts it into small pieces. This point is referred to as "Mill- 

 ing time." The cut pieces of curd are then stirred frequently to prevent 

 them matting together, and when the curd has mellowed and the drip- 

 pings of whey shew from 1.0 to 1.2 per cent of acid, salt is added at the 

 rate l^/^ to 2V2 lbs. to tiie 1000 lbs. of milk. This is referred to as 

 '■' Salting time." The temperature of the curd from dipping to milking 

 is about 9-l°F (34°C). After milling, the curd is allowed to cool 

 gradually to about 85° F (30°C) and it is put into the presses at a tem- 

 perature of 82° to 84°F (28°-29°C). The cheese is turned once and 

 kept m the hoops overnight, afterwards it is removed to the curing room. 



Microscopical Examination of Curd and Cheese at Different Periods.^ 



1. At Cutting. — Sections shewed the cheese to have a granular 

 structure with numerous clear spaces. The lactic acid bacilli occurred 

 singly, in pairs or in small groups of 5 to 10 cells, they were not numer- 

 ous, twenty to thirty fields (using the l-12th oil immersion lens) were 

 often searched before any organisms were seen. See Fig. I. 



2. ^Yhen Cooling Temperature was Readied. — There was no notic- 

 able difference in the open or closeness of texture of the curd. The 

 bacteria were about the same in number as at cutting time, but now and 

 then larger groups were present. See Fig. 2. 



3. At Dipping. — The texture of the curd was slightly coarser, and 

 there was a noticeable increase in the number of bacteria, nearly every 

 field of the l-12th oil immersion lens shewed bacilli, many in short chains 

 or clusters, and here and there small clumps or colonies containing from 

 20 to 100 cells. See Fig. 3. 



4. At Milling. — The texture of the curd has undergone considerable 

 change, instead of the granular texture it has now become quite flaky, 

 giving the appearance of layers or lamin;» closely pressed together. (See 

 Fig. 4.) When this stage is reached cheese makers term the ^curd 

 " meaty " and it can be torn into long flaky strips. It was almost im- 

 possible to find a single field in which there were not large numbers of 

 bacteria. The increase in numbers since dipping time was very marked. 

 The bacilli occurred in small chains and in small and large clumps or 

 colonies. See Fig. 5. 



5. At Salting. — The texture of the curd was not so markedly 



flakj'. 



The bacteria increased in numbers, larger clumps were seen, — some 

 very large ones near tihe op'en spaces in the cheese. See Fig. 7. A 



