Thermal death point of moist and dry conidia of Penicillium.
| PENICILLIUM IN 10 CC OF TOMATO BOUILLON. | ||||
|---|---|---|---|---|
| No. of experiment. | Temperature. | Time of heating. | Time before germination. | Period of observation and developments. |
| °C. | Minutes. | Days. | ||
| 1 | 85 | ½ | 3 | Dark strings from spores; 9 days; no development. |
| 2 | 80 | 1 | ||
| 3 | 75 | 1 | ||
| 4 | 70 | 5 | ||
| 5 | 65 | 5 | 3 | Dark strings running from spores; 9 days; growth normal, spots on surface. |
| 6 | 60 | 5 | 3 | Do. |
| 7 | 55 | 5 | 3 | Do. |
| PENICILLIUM IN 10 CC OF KETCHUP. | ||||
| 1 | 100 | 3 | ||
| 2 | 100 | 2 | ||
| 3 | 100 | 1 | ||
| 4 | 100 | ½ | ||
| 5 | 100 | Instant. | ||
| 6 | 85 | ½ | 2 | Colonies on sides; 8 days; surface covered, green. |
| 7 | 80 | 1 | 2 | Do. |
| 8 | 75 | 1 | 2 | Do. |
| 9 | 70 | 5 | 8 | Colony on surface. |
| 10 | 65 | 5 | 9 | Do. |
| 11 | 60 | 5 | 3 | Colonies on sides; 8 days; surface covered, green. |
| 12 | 55 | 5 | 4 | Do. |
| 13 | 2 | Ring around sides; 3 days; surface nearly covered. | ||
| DRY CONIDIA. | ||||
| 1 | 100 | 10 | 4 | Rough appearance,like that in ketchup. |
| 2 | 100 | 15 | 4 | Do. |
| 3 | 100 | 20 | 7 | Slight growth. |
| 4 | 100 | 25 | 10 | Growth barely perceptible. |
| 5 | 100 | 30 | 10 | Do. |
| 6 | 100 | 35 | Conidia stained readily, showing they were dead. | |
| YEAST. | ||||
| 1 | 55 | 5 | 2 | Wrinkled film; liquid turbid. |
| 2 | 60 | 5 | 2 | Do. |
| 3 | 65 | 5 | 2 | Thin, smooth film; liquid clear. |
| 4 | 70 | 5 | ||
| 5 | 75 | 5 | ||
| 6 | 100 | Instant. | ||
The moist heat was very effective in destroying the vitality of the conidia of Penicillium, the death point being 27° C. higher than the maximum temperature for germination as given by Sykes. The heating was more effective in destroying germs when applied to bouillon than to ketchup, no development taking place for any temperature above 65° C., even when applied for a short time.
In the ketchup the lower temperatures for the longer periods of time were more effective in checking the development, even though they did not destroy the vitality. In the ketchup, with the exception of Nos. 9 and 10, the colonies started invariably along the sides of the flasks. The greater access of air to those on the sides would account for this. The conidia on the sides of flasks Nos. 9 and 10 must have been destroyed, as no development took place in either case except in the center of the surface.
The dry conidia were destroyed at 100° C. when heated for thirty-five minutes; they did not reach a normal development in any case, even when heated for only ten minutes, many of the conidia being destroyed by this treatment. Where development failed to take place, the conidia were stained with a water solution of eosin, so as to be sure that the effect was death, and not an arrested development.
The results of the tests do not agree with those obtained in factory practice, where the ketchup is cooked at 100° C. for at least forty minutes and sometimes for fifty or fifty-five minutes, depending on the consistency of the pulp.
HISTOLOGICAL STRUCTURE OF KETCHUP.
In ketchup are found parts of all the various tissues of the tomato broken into fine pieces by the action of the cyclone. Although the sieves take out the seeds, skins, and any large pieces, particles of the various tissues are present in size sufficient for identification. Among the distinctive features are the red crystalline bodies in the parenchyma, which serve to a certain extent to distinguish the parenchyma from that of other plants which might be used for adulteration, and serve also to differentiate the natural from the artificially colored ketchup. Some of the red dye used colors all protoplasm indiscriminately, even that of the fungi present, and as a colored ketchup is usually poor stuff, containing many fungi, the mold filaments, yeast cells, and bacteria receive their share of the color. Other red dye used is in the form of fine powder, which does not go into solution, but is distributed as irregular particles which are distinct from the red crystalline bodies.
Good ketchup made from whole tomatoes has a clean appearance readily distinguishable under the microscope; but the poor ketchup has usually a superabundance of fungi present, fully developed colonies of mold, many forms of conidia, besides yeast-like cells, and different forms of bacteria. All of these may be dead, but neither preservatives nor dosage of odorous spices can disguise their presence. In some of the ketchup examined, which was put up in attractive form and labeled as being made from the whole tomatoes, and which had the appearance and odor of good ketchup, the microscope showed the presence of such quantities of fungi as to leave no doubt that the tomatoes were spoiled when cooked. It is presumable that some of the dealers placing this sort of stuff on the market do not know its condition themselves, and either buy their pulp from other factories or trust its manufacture to employees whose only care is that the ketchup shall have a bright color and shall “keep.” Some of the mould filaments and conidia are distorted in the same way as those of the Penicillium are when grown in ketchup to which sodium benzoate has been added.