MODIFIED MILK AND MILK PRODUCTS 121 



sporogenes. All these are carried out as for milk samples. 

 Pathogenic bacteria such as B. tuberculosis, B. diphtheriae and 

 B. typhosus occasionally have to be examined for, using the 

 same procedures as described under milk. 



In addition B. enteritidis and other Gaertner group bacilli 

 will occasionally have to be examined for. A number of food 

 poisoning outbreaks have been ascribed to the consumption of 

 ice-cream, and some if not most of these are due to infection of 

 this food with Gaertner's group bacilli. The method of exami- 

 nation to employ is given in Chapter VIII. 



Bacterial standards. 



It is not at present practicable or expedient to lay down 

 definite standards of number of bacteria or of special kinds to 

 be permitted in ice-cream. Rough standards as a guide to the 

 sanitary conditions and cleanliness precautions observed would 

 however be of great utility. For these purposes standards based 

 upon the number of B. coli group organisms would probably be 

 of greatest service. 



Buchan has suggested that ice-creams made under clean 

 conditions : 



(a) Should not contain more than 1,000,000 organisms 

 per c.c. capable of growing on nutrient gelatine (reaction + I per 

 cent.) at 20 to 22 C. in three days. 



(b) Should not contain more than 1,000,000 organisms 

 per c.c. capable of growing on nutrient agar (reaction -f I per 

 cent.) at 35 to 37 C. in two days. 



(c) Should not produce acid and gas in bile-salt glucose 

 broth with a less quantity than 0*1 c.c. 



(d} Should not contain the Bacillus enteritidis sporogenes in 

 less than 10 c.c. 



(e} Should not contain streptococci in less than O'ooi c.c. of 

 ice-cream. 



