COOLING HOT-BOTTLED PASTEURIZED MILK. 



31 



Table V. — Laboratory cream-line experim.ents showing comparison of raw milk and milk 

 pasteurized at 145° F. for 30 minutes followed by various methods of cooling. 



Experi- 

 ment Xo. 



Milk and process. 



Cream in 500 

 c. c. cylinder 

 after 24 hours' 

 refrigeration 

 at 45° F. 





(•Raw '. 



C.c. 



64 5 



1 



Pasteurized: 



64.5 

 65.0 

 64 5 





Cooled stowlvin air hiast for 45 minutes 





Held above 105° F. for tliree hours and cooled in ice water 





Raw 



65.0 



62.5 

 52 5 



2 



Pasteurized: 



Cooled in 15 seconds to 50° F 









Held al'ove 100° F. for li- hours 



52 5 





Raw milk lost ' 





3 



Pasteiurized: 



83 





Cooled slowly for 30 minutes in air Mast, then cooled quickly in brine 



85 

 90 





Raw milk lost 





4 



Pasteurized: 



Cooled in 15 seconds to 50° F 



75 





Cooled slowly in air blast for 21 hours, then cooled in ice water 



69 





Held al)Ove 100° F. for '2h hours and cooled in ice water 



75 





Raw '. 



80 



- 



Pasteurized: 



Cooled in 15 seconds to 50° F 



68 





Cooled slowly in air blast for 2 hours 



55 



5 



After cooling in air blast for 2 hours the milk was cooled quickly in brine 



to 50° F. 

 Held above 100° F. for 5 hours 



62 

 55 





After holding above 100° F. for 5 hours the milk was cooled quickly in 

 brine to 50° F. 



62 



A study of the results shown in the table above indicates that 

 cream-line formation is a variable factor. Sometimes it was reduced 

 by pasteurization, even when the milk was cooled to low tempera- 

 tures within 15 seconds, and at other times there was no difference. 

 In some experiments the cream liae was slightly less on milk cooled 

 slowly. 



These laboratory experiments do not exactly duplicate conditions 

 of air cooling on a commercial scale, for in no case was the hot 

 pasteurized milk cooled to 50° F. (10° C.) within three hours, as it 

 was in our later experiments. Throughout our experiments on a 

 small coEomercial scale, when the milk was cooled to that tempera- 

 ture within the time named no apparent reduction of the creana layer 

 was observed, and the cream line was always distinct. When milk 

 stood at temperatures above 80° F. (26.7° C.) for several hours 

 without agitation, some of the melted buttcrfat rose to the top of 

 the bottle and on cooling formed a smaU lump of butter. This was 

 observed, however, when the cooling process was begun immediately 

 after bottling, even though tlu^ cooling was gradual. 



A.S to the (iffcct of tlic i)rocess on (lie flavor of the milk, it may bo 

 said that there was no more noticeable flavor than is the case with 

 milk pasteurized iirid cooled mpidly, (except wh(>ii thci milk was held 

 above 100'-' F. {'.ilX^ C.) for several liours. This was the case in 



