THE INFLUENCE OF MANUFACTURING OPERATIONS ON THE 

 BACTERIAL CONTENT OF ICE CREAM 



FREDERICK W. FABIAN AND ROY H. CROMLEY 



Technical Bulletin No. 60 



INTRODUCTION 



The importance of ice cream && a food is daily increasing. Th'e mami- 

 facture of ice cream toas risen from a back^doior and cellair indiisti'y to 

 one of greait importance. From a preliminary statement from the Cemsns 

 Bureau of the United States Department of Oomm'eree the following sta- 

 tistics are available: From 3,47G establishments engaged in tlie manu- 

 facture of ice cream in 1919 were reported products valued at $189,414,- 

 000. This iis compared with 1914 in which yeair 2,437 establishments re- 

 ported products valned at 155,983,000. This represents lan increase of 238 

 per cent in valne over a five year period. In Michigan between 1914 and 

 1919, the ice cream industiy shows a growth from 60 establishments man- 

 ufacturing a product worth |1,803,000 in 1914, to 92 establishments 

 "tvbose product was valued at |5,30'2,000 in 1919, or an increase of 194 per 

 cent in Value oveo* a five year period. 



It w^ill thus be seen that the importance of ice cream a® a food ha.s in- 

 creased considerably in the piaist five years. As the consumption of ice 

 cream increases no doubt there will be more detailed studies made of it 

 from the chemiioal and bacteriological standpoint. The dhemieal compo- 

 sition is fairly well defined in most states but there is a conspicuous lack 

 of bacteriologi'oal standairds at the present time. There seen-is to be no 

 well defined saiuitairy code \as in the case of milk and water. As our sani- 

 tary knowledge of ice cream increases sb that an intelligent standard will 

 be possible, such a sanitary code will be forthcoming. One of the impor- 

 tant things that a sanitary code wili have to take into consideration is 

 the influence of the manufacturing operations on the bacterial count. 



Su'cfh a study not only reveals the sanitai*y quality of the product, but 

 aiisio teUs something of the metliodis employed in making the ice cream. 



PREVIOUS WORK 



Pennington and Walter (1) were among the first investigators to 

 make a baicteriological study of each step in the process of mlanufacturing 

 ice cream,. Only one sample was analyzed, h'owever, sio that no definite 

 cooiiclusionis were drawn. They reported that although the cream was 

 pasteurized twice, once before it reached the city aind ag'ain as soon as it 

 was received, "nevertheless vegetative streptococci are found in the fin- 

 ished process." Continuing they slay that, "the proportion of streptococci 



