i8o Journal of Agricultural Research voi. xxii, no. 4 



factor. Obviously this product, 'even at its maximum moisture content, 

 presents a marked contrast to laboratory media as usually prepared. 

 Nevertheless, corn meal has been so often found an unstable product that 

 it is commonly milled only for consumption within a few weeks or by 

 methods intended to eliminate the most readily fermentable portions of 

 the grain. 



Under ordinary conditions of handling, spoilage in this product ap- 

 pears in one of the following forms: Souring, rancidity, mustiness, the 

 formation of clumps or balls, extensive concretions which may involve 

 the solidification of an entire bag, or the formation of a hard, cylindrical 

 outer mass with the center loose and mealy. Heating occurs only in 

 the wettest samples. Much com meal, if held beyond a very short 

 period, develops a musty, moldy, or sour odor and shows occasional 

 balls or masses of meal held together by mold, which bring about losses 

 in palatability and market quality in the product. Such changes as 

 rancidity and the formation of extensive concretions into moldy masses 

 are so obviously due to high moisture content and involve such losses 

 that they have been almost eliminated from commercial practice. 

 When losses occur the meal is found to carry more than a critical mois- 

 ture percentage. This may be due either to milling com which is in- 

 sufficiently dried or to the storage of the meal under conditions which 

 will maintain a moisture content above the danger point. For the 

 samples used in all series reported here this figure was approximately 



13 per cent (2). 



CULTURAL EXAMINATION 



In routine cultural examination reported here, plain agar was used 

 for bacterial counts, wort agar for mold counts, and dextrose-litmus 

 shake agar to determine acid, gas, and anaerobic growth. The presence 

 of particular organisms was determined by tlie use of special methods 

 on special media. Experimentation covered a range wide enough to 

 justify the restriction of routine cultures to the media already noted. 



After comparative study of many series of cultures. Table I is intro- 

 duced as giving a group of cultural results fairly typical for commercial 

 meal in sound, merchantable condition. The nine samples reported 

 were purchased in different retail stores of Washington, D. C, during 

 October and November, 1920. Four of them were yellow and fairly 

 coarsely ground. The white meals were softer or more finely ground. 

 All were bolted. All showed by microscopic examination traces of 

 both bran and germ, although these portions were scanty in certain 

 samples. The history of the samples was not obtained. 



These samples were sound in appearance and odor. There was no 

 evidence of the multiplication of microorganisms. Among the bacterial 

 colonies micrococci, members of the mesentericus and of the colon- 

 aerogenes groups were characteristically present. Special tests in cab- 



