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A study of the causes of periodic abnormalities of a high grade pasteurized milk supplyRubin, Benjamin Arnold January 1938 (has links)
The causes of acid liquefaction in a high grade pasteurized milk were investigated.
1. Liquefying milk produced much less acid and had a much lower plate count than normal milk.
2. <i>Bacillus albolactis</i> was found regularly in the milk. It made up a much larger percentage of the total flora in liquefying than in normal milk.
3. Associated growth experiments showed that <i>Strep. lactis</i> could control the liquefying activities of <i>Bacillus albolactis</i>.
4. Pasteurization experiments showed that milk heated for 20 minutes at temperatures higher than 61°C. would undergo acid liquefaction. This appeared to be due to the increase in the percentage of <i>Bacillus albolactis</i>.
5. Inoculation of pasteurized samples with <i>Strep. lactis</i> prevented acid liquefaction.
6. Comparison with a type species showed that the strains of <i>Strep. lactis</i> repeatedly isolated from the milk studied were of the <i>tardus</i> variety.
7. The liquefaction was probably primarily due to an increased percentage of <i>Bacillus albolactis</i> brought about by pasteurization; the lack of the type of species of <i>Strep. lactis</i> and the absence of lactobacilli might also have been contributing factors. / Master of Science
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