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Summary The investigation had as its principal objects, determination of the microbiological effectiveness of the chlorination of polluted water supplies used for buttermaking, the influence of high chlorine dosages on butter flavour and an examination of the reproducibility of butter grading by subjective methods. A preliminary trial in which pasteurized sweet cream was made into butter using polluted as well as chlorinated water, revealed that there were marked differences in the condition and quality of the finished product. Butter washed with contaminated water developed rancidity within twenty‐one days at 37 to 41 °F. whereas water from the same source, but which contained 5 p. p.m. residual chlorine, resulted in butter which retained a pleasing flavour and aroma for six weeks. In the main experiment, six duplicate lots of unsalted butter were made from ripened cream, using treated and untreated water from the same source, with identical buttermaking methods. The untreated water contained large numbers of psychrophilic bacteria, including Pseudomonas putrefaciens. These organisms grew actively in unsalted butter held at 45 to 50°F. Chlorination of the water with varying dosages of from 10 to 200 p. p.m. available chlorine, sixteen hours before use, resulted in practically a complete destruction of the spoilage organisms. The cream used during the main experiment was ripened at 40 to 50°F. for two days after pasteurizing by the H. T.S. T. method before churning. On microbiological examination, the butter produced from this cream was found to contain large numbers of spoilage organisms, and became rancid within four weeks when stored at 45 to 50°F. However, the microbiological results indicate the superior quality of those butters made with chlorinated water. A consensus of the grading results obtained, substantiates the anticipated superior quality of butter made using chlorinated water, compared with that made with an impure supply. No chlorine taint was detected in the butter, although water containing as much as 100 to 200 p. p.m. residual chlorine had been used in preparing two of the samples. The arbitrary nature of subjective grading is reflected in the differing conclusions arrived at by individual members of the graders' panel.

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SUMMARY: Colony counts at 30° were greater than 10 times those at 37° in a high proportion of rinses of washed milk cans, the difference being most marked in those containing milk scale, where 58% of the colony counts at 30° exceeded 106/can. A high proportion of the microflora was composed of thermoduric bacteria. Of 895 cultures from the milk scale, 33% were micrococci, 28% corynebacteria, 22% streptococci, and 9% were Gram‐negative rods. Though aerobic sporing rods constituted only 5% of the microflora of the milk scale, they were present in large numbers and unsatisfactorily washed cans probably constitute one of the main sources of these organisms in milk.