486 STATE BOARD OF AGRJCULTURii 



Wcterial count. The authors believe that the T\'"ork presented in this 

 piaiper represents wihat 'can be expected in a samitary way from a' coan- 

 miercial ice cream factory. This particular faictory was chosen for this 

 work becanse to our minds it represiented lan average up-to-date factory. 

 The output is. not as great as that of the largest factories, noir is tihe out- 

 put so small as to exclude piping and other necessary machinery, not 

 usually found in smiall factories, but Wihicli miay be a gi-ieait source of 

 bacterial €ontamin(ation. The oiuti^uit averages about 6,000 gallons per 

 day in summer and 2,000 gallons per day in winter. The machinery con- 

 sists of five 80 quiairt, and one 40 quart Miller freezers ; two 500 gallon 

 Elyria glass-lined pasiteurizers ; one 400 gallon Manton-'Gravlin homogen- 

 izer; one 500 gallon Miller cooler ; an'dfour 1,000 gallon glass-lined Elyria 

 hoMing vats. In addition to the above eqiiipmeait there are about 350 

 feet of iconlnecting piping. 



After each day's run, the piping and machinery were first rinsed with 

 cold water and then witli boiling 'water. Live steam .was then run through 

 the piping. It was then taken down and scoured with a satisfactory com- 

 merci'ail cleaning powder. When they were ready to use it the piping was 

 reassembled and riinsed with hot wiaiter and then treated with flowing 

 steam. In this way it was .possible to keep the contamination down to a 

 minimum. 



PLAN OF WORK 



Thoroughly mixed samples of cream, condensed milk, and gelatin were 

 taken from theanaterials going into each .batch and plated on agar. This 

 was done to find out tlie bacterial content of the iraw product. The above 

 constituents contr'ibute tlie greatest number of bacteiia to ice cream as 

 previous workers have shown. (Stiles and Pennington (5), Gordon (6) 

 and Hammer (2).) The mix made from these materials was then preipared 

 in the I'egular way and given a aiumber which is called the "batdli" num- 

 ber. Samiples were lagain taken of tlie mix just before paisteurization. 



The mix was then pasteurized at 65.6° C (150° F) for 30 minutes and 

 samples taken and plated. The mix then passed through the homogenizer 

 under pressure ranging from 2,500 to 3,000 pounds. Samples were taken 

 again at the end of this operation. From the homogenizer the mix passed 

 to the cooler wihere it wais cooled to 10° C (50° F). Samples were taken 

 before land after cooling. The mix then passed to the holding vat where 

 it was held for 24 hours at 2° C (35.6° F) for aging. Samples were taken 

 at the beginning and at the end of the aging period. Frani the holding 

 vats the mix went to fii'eezers and samples Avere taken jaist before it was 

 frozen and again as it was leaving the freezers' in a semi-solid state. 



It was our original plan to follow the ice cream through at least four 

 weeks of storage but this was abandioned af tea* several of our sample con- 

 tainers liad been shipped out by mistake. However, considerable previous 

 work by Stiles and Penningto.n (5), Gordon (6), Hammer (2), Esten 

 and Maison (7) and Ellenberger (8) has covei^d this x>hase of the problem 

 quite completely. The isamples collected according to the above scheme 

 were taken to the laboratory and plated immediately on plain agar and 

 incubated for 48 hours at 87° C. 



It will be seen that ouir plain of work starts with tlie .raw miaterials 



