The washing is the most important mechanical operation in making pulp or
ketchup in order to get a clean product. It is the weak spot in most
factories, but fortunately is the one that can be most easily changed.
The ideal washer is one that first receives the tomatoes in a tank,
holding them for a sufficient length of time to soak and to loosen the
dirt, and then submits all parts to a thorough spray under strong
pressure. Most washers do not meet these requirements. In many cases the
tomatoes are either not dropped into water, or go in and then out again
so quickly that they are only made wet and bright, but not clean, then
pass under a few cross-sprays, each of which does not deliver a stream
more than an inch or so in width, the total spraying not being active
over a space of more than six inches and only from above. Some machines
do not actually spray the fruit more than one or two seconds. In some
cases, it is not so much the fault of the machine as that of the owner
in over-speeding and over-loading it. Most machines use a sufficient
volume of water, but not under sufficient pressure, nor over a
sufficient area. One of the best washers in use is a slight modification
of the cylindrical washer used for removing the lye and peel from
peaches. It consists of a cylinder about two feet in diameter and twelve
feet long, made of a specially corrugated iron. The corrugations are
sharper than the ordinary pressed metal used for building and siding,
and in addition they are perforated at frequent intervals. This cylinder
is mounted on a slight incline. The tomatoes are fed in at one end and
the revolving motion causes their discharge at the other. The effect of
the corrugation is to cause each tomato to turn over and over in its
course and thus avoid all sliding. A spray pipe passed through the
entire length and, when provided with the proper nozzle, insures a
thorough washing, the tomatoes being under actual sprays from six to
twenty times as long as in many machines that are now in use. The water
pressure should not be less than sixty pounds per square inch and is
better above one hundred pounds if fine perforations or nozzles be used.
In nearly every case it is necessary to augment the natural pressure by
an auxiliary pump. The principle of the strong pressure is seen in using
a hose without a nozzle to wash a floor and one with a nozzle and strong
pressure. In the former case it does not clean, while with the latter it
does and with less water. The washer just described is too vigorous for
tomatoes for canning, as the treatment is too rough. If the tomatoes are
soft or badly cracked, it causes considerable loss, but not of material
that should be used in ketchup. The strong sprays will also cut off
adherent mold and soft rot. A thoroughly good washer will do about
nine-tenths of the work for the inspectors. During the past season some
modifications have been made of this washer in the east. The machine has
been enlarged, but better results would be obtained by using a greater
number of small ones. Again, some washing machines have been
ineffective, not on account of any defect, but because of over-speeding.
The vigor with which the washing is done is always apparent in the
finished product. The poor washing usually given to tomatoes for
canning, accounts in a measure for the relatively large numbers of
organisms found in ketchup made from trimmings.