8 N. H. Agr. Experiment Station [Bulletin 256 



The total number of points of contamination are much fewer in num- 

 ber for the dry method than for the wet. The rate of cooling in the dry- 

 process is almost instantaneous as compared to several hours for the 

 wet tank. The final bacteria count of milk is invariably higher in the 

 wet-tank method, due to the slow cooling process which allows rapid 

 multiplication of the original bacterial content acquired through the 

 milking and handling process. 



The contamination factor of surface coolers is no greater, and gen- 

 erally not so great, as that of many other utensils used in the milk- 

 handling process. This, after all, is a matter of cleaning and ster- 

 ilizing utensils rather than a factor of refrigeration equipment; and a 

 good percentage of the coolers tested under actual farm conditions have 

 shown a high degree of cleanliness. 



It seems evident that if the milk contains less than 5,000 bacteria per 

 c. c. at the time the cooling operation starts, any of the various ap- 

 proved methods of cooling milk to below 50° F. and holding below this 

 temperature, will insure desirable quality milk (from a bacterial stand- 

 point) . 



As an example, a 40-quart can of milk which required l 1 /!' hours to 

 cool to 50° F., and 4Vo hours to reach 40° F., was delivered at the lat- 

 ter temperature to a milk receiving station 15^ hours after production. 

 It contained only 500 bacteria per c. c. 



A can of milk cooled on a different farm using the same method, but 

 containing 75,000 bacteria per c. c. at time of production, increased to 

 245,000 bacteria per c. c. in the 16 hours the milk was left on farm. 



Where the practice is followed of using a surface cooler, with well 

 water as a cooling medium, and with cans placed in dry storage, the 

 bacterial increase during 12 hours' storage may be as low as 8 per cent, 

 and it may be as great as 610 per cent. 



The initial contamination of the milk was found to be due in most 

 c;tses to dirty milking machines, dirty cans, and dirty cows. In one 

 instance, had a certain 40-quart can been filled with milk, it would 

 have added 81,000 bacteria to each c. c. 



Bacterial counts taken on milking machines as soon as the machine 

 was removed from the cow showed counts ranging from 100 to 570,000 

 bacteria per c. c. {Purnell Fund) 



Costs of Retailing Grain 



Grain store credit costs approximately double that of banks. Cash 

 customers at such stores doing a credit business pay for a service they 

 do not obtain, according to the study by E. H. Rinear of operating 

 costs of retail grain stores in New Hampshire. Further highlights of 

 the work which is published in Station Bulletin 251 are as follows: 



The cash price of corn becomes higher as the percentage of credit 

 sales increases in a retail store. Grain prices shifted less than 15 times 

 during the same year that the Boston wholesale market price changed 

 40 times. Store prices lagged an average of 2.6 weeks as the market 

 moved upward and 4.8 weeks when it went downward. 



An average of $870,500 was carried in accounts and notes receivable 

 by 89 grain stores. The average turnover of accounts receivable was 38 

 days. Bad debts ranged from none up to $4,000 per store. 



