The finishing machine should be operated slowly, so that the pumice will come out dry. The small receiving box under the finisher should drain completely so that it does not have a foot of cold pulp lying in it when the finisher is idle.
Screen Metal for Finisher
The best kind of screen for the finisher is made of monel metal. The brass screen is more common; however, the same thing can be had in monel metal, and it does not offer the opportunity for metallic contamination that the brass screen does. The monel metal screens wear very well and have proven themselves to be satisfactory in every respect. Aluminum should not be used, as it is eaten up by the tomato acid and will not last long.
Effect of Finishing on Mold Count
The opinion has often been expressed that the brushing of the pulp through the fine meshes of the screen breaks up the small clumps of mold and scatters them in small threads throughout the mass, thus increasing the mold count, since this count is not based on the total quantity of mold present, but upon the number of microscopic fields containing molds. Thus, by scattering the mold, instead of allowing it to be retained in comparatively large clumps, the number of microscopic fields containing mold threads would be increased.
Although one might reasonably expect this to take place, experiments have proven that it does not take place. Several years ago, in order to determine this point, I analyzed thirty batches of catsup just before entering the finisher and again just after coming through the finisher. In every case the percentage of microscopic fields containing molds after finishing was practically the same as before finishing. A cone-shaped finisher with three revolving brushes and fine mesh screen was used for this test.
Finishing Before Cooking
Although the finishing machine, if properly tended to, is probably responsible for very little of the spoilage in pulp, it has been suggested to use the finisher before the pulp is condensed. Then the pulp can be drawn direct from the kettle to the cans, and the chance of contamination and cooling in the finisher can be eliminated. This idea is well worth experimenting with, as the pulp could be filled at almost the boiling point. I have not tried out this idea, but offer it here as a possibility which has advantages which are well worth looking into. Packers who are having spoilage trouble which they cannot attribute to other causes would do well to experiment with it. As to whether both the pulp machine and finisher would have to be used before the cooking, or whether the finisher alone would do, providing the tomatoes were previously crushed, or cooked in a “breaking tank,” would have to be determined by experiment. The method may be in use now by some packers; however, I have not heard of it being used.