10 



BULLETIN 563, U. S. DEPARTMENT OF AGRICULTURE. 



Table IV. — Variation in the bacterial content of samples of ice cream taken from gallon 



lots held in cold storage. 



Age of ice 

 cream. 



Sam- 

 ple 

 No. 



Number of 



colonies on 



duplicate 



plates. 



Average 



count 



per c. c. 



Variation between 



lowest and highest 



counts. 





1 

 2 

 3 



4 

 5 

 9 



7 

 8 

 9 



64 

 117 

 120 

 109 



95 

 102 

 138 



77 

 131 



79 



96 



118 

 118 



97 



129 



7,150 

 11,700 

 10,800 

 10,350 

 10, 650 

 10,200 

 11,750 



7,700 

 13,000 



Samples 1 and 9, 

 81.81 per cent. 



< 





One month 



1 



2 

 3 



4 

 5 

 6 



7 

 8 

 9 



118 

 106 

 112 

 111 

 110 

 104 

 118 

 102 

 117 



117 

 112 



106 



11,800 

 10,600 

 11, 200 

 11,400 

 11,100 

 10,400 

 11,800 

 10,200 

 11,150 



Samples 7 and 8, 

 15.68 per cent. 





1 

 2 

 3 



4 

 5 

 6 

 7 

 8 

 9 



76 

 66 

 76 

 92 

 79 

 73 

 70 

 75 

 76 



77 

 76 

 70 

 68 

 82 

 72 

 80 

 76 

 92 



7,650 

 7,100 

 7,600 

 8,000 

 8,050 

 7,250 

 7,500 

 7,500 

 8,400 



Samples 2 and 9, 

 18. 31 per cent. 



VARIATION IN SAMPLES TAKEN DIRECTLY FROM FREEZER. 



The question of whether a sample of ice cream taken from a 

 freezer represents in bacterial content the entire . contents of the 

 freezer is one of considerable importance. To obtain information 

 on this point 10 series of from 6 to 10 samples were taken from the 

 large commercial freezers in an ice-cream plant. The samples were 

 taken in the following manner: As soon as the cream was frozen 

 and ready to flow into the final containers for hardening, the gate 

 was opened and about 1 pint allowed to flow out. The first sample 

 of about 50 grams was then taken by allowing the partially frozen cream 

 to flow into a sterile salt-mouth bottle. About 1 gallon of ice cream 

 was then allowed to flow out and a second sample taken. The remain- 

 ing samples were secured in a similar way, the last one being taken 

 from the very last portion. All were immediately iced and taken 

 to the laboratory, where they were plated in the manner previously 

 described. The results are shown in Table V. 



