Bread, bakehouses, and bacteria : reprints of various papers / by F. J. Waldo and David Walsh.

  • Waldo, Frederick Joseph, 1852-
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: Bread, bakehouses, and bacteria : reprints of various papers / by F. J. Waldo and David Walsh. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    during baking to a maximum temperature of 73° to 86° C. (163-2° to 186'8° F.) in a quartern, and of 86° to 95° C. (190-2° to 203° F.) in a half-quartern loaf. It is known that most bacteria are not destroyed by an exposure to the temperatures above mentioned as the average for the centre of a loaf during baking. The death point of bacteria has been expressed generally by Koch and Wolfhiigel in the following passage: 11. Sporeless bacteria are destroyed in one and a half hours by hot air at a temperature slightly exceeding 100° C. (212° F.). 2. Spores of fungi require one and a half hours at 110° to 115° C. (230° to 239° F.). Spores of bacilli require three hours at 140° C. (252° F.).’* It should be noted that these state- ments apply to dry heat only. In the middle of the loaf there is presumably moist heat, which is, of course, more destructive to organisms, and on that account we must make a considerable reduction in the figures of Koch when we apply them to fungi and their spores inside a loaf. After making ample allowance it is obvious that if the temperatures found by us in the centre of loaves be correct it will be safe to predict, on theoretical grounds alone, that bacteria and their spores need not necessarily be destroyed by baking inside a loaf. Cultivations. The next step was to ascertain whether ordinary bread contained organisms or their spores in a state of vitality. It is clear that even if the actual organisms were destroyed by baking, while their spores survived that process, there is nothing to prevent the subsequent development of the spores. The loaves used in the following experiments were * ‘Micro-parasites in Disease,’ vol. cxv., New Sydenham Society, p. 525. 3