CONVEYING THE CONDENSED, STRAINED, OR CRUSHED TOMATOES TO THE FINISHING
MACHINE AND FINISHING SAME
Conveying to Finisher
The fewer pipes and receiving tanks the condensed pulp passes through
before being filled in the cans, the better. All of this conveying and
finishing equipment offers possibilities of contamination, and allows
the cooked pulp to cool to some extent before it is filled. Eliminate as
much equipment as possible between the cooking kettle and the filler,
and have the pulp enter the cans at at least 170 degrees F., and if
possible, at 180 degrees or above. A receiving tank between the cooking
kettles and the filler should be dispensed with if possible, and the
finishing machine draw the cooked pulp direct from the kettle by means
of a short line of enamel lined pipe.
Receiving Tanks
Unfortunately the arrangement of many plants is such that it is almost
necessary to use a receiving tank; at least in such cases it would be a
disadvantage not to have one. Where a tank must be used here it should
be in such a position that it is easily accessible, so that it will not
be necessary for a man to be an acrobat to get into it, inspect it, and
see that it is kept clean, and that an inch of pulp is not allowed to
lie in it and get cold while waiting for another batch to come down.
The best kind of a tank for this purpose is an enamel or glass-lined
tank with a rounded, tapering bottom so that it will almost drain itself
completely, and what little adheres to the sides can be scraped down in
a few seconds if it is necessary to wait five or ten minutes for a
fresh, hot batch to come down. Even if it isn’t scraped at all it will
probably not cause any trouble in a tank like this. Wooden tanks will
do, of course, but it would pay a packer who must use a tank here to
throw out his wooden one and put in a tank such as is recommended above.
It is hard to construct a wooden tank so that it will drain well; in
fact, nine out of ten scarcely drain themselves at all; they are never
kept as clean as they should be, and wet wood seems to be a favorite
spot for molds to grow, so that frequent scrubbing is necessary if it is
kept sanitary. It is most important to inspect the receiving tank
carefully before it is first used in the morning, as they sometimes mold
slightly over night, or dirt falls into them from overhead. A steam hose
should be kept close to a wooden tank to sterilize it at night after it
is scrubbed out.
Finishing
Whether or not a receiving tank is used, the finishing machine should be
as close to the cooking kettles as possible, and should receive constant
attention from a careful operator who can comprehend to some degree the
importance of keeping it clean. If the filling department gets ahead of
the cooking department and is obliged to wait fifteen minutes or a half
hour for a fresh batch of pulp to come down, the man who tends to the
finisher should take it apart at once, wash it off, steam it off
thoroughly with the steam hose, and put it together again so that it
will be clean and practically sterile when it receives the next batch.
Otherwise the screen and the brushes will be clogged up with cold pulp
when the fresh batch comes down, which is a bad condition, especially if
the pulp is not to be sterilized after it is filled, which is usually
the case with 5–gal. pulp. Even though the finisher is operated
continuously through the day, it should be taken apart and cleaned at
least twice during the morning and twice during the afternoon.
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.