The laboratory of the National Canners’ Association is frequently asked
to examine samples of tomato products to determine whether or not they
comply with the Government requirements. In examining these samples we
use the Government method (the Howard method), but do not participate
in the discussions regarding its merits and shortcomings.
It is our experience that skilled analysts can check themselves and
each other with reasonable accuracy, and it is our duty to tell the
manufacturer whether his product is legal. Should the Bureau of
Chemistry adopt some other method as preferable to the Howard method,
it would be our duty to use the new method and continue to serve the
industry by telling the manufacturer whether samples submitted by him
would pass the Government tests.
With a full understanding of our attitude in this matter many
manufacturers of tomato products send samples from time to time for
examination. It is made plain in every instance that the results
obtained by the examination of a particular sample refer only to the
batch from which that sample was taken and may give no indication of
the character of any other batch.
Some manufacturers of tomato products use the Howard method as a check
on their factory control. For this purpose it is not satisfactory to
have samples examined in a laboratory located at a distance from the
factory. Even if several samples are examined from a day’s run, they
probably do not represent all the pulp manufactured on that day. It
sometimes happens that one wagonload of tomatoes is almost entirely
free of rotting material, whereas the succeeding load contains a
considerable amount. Even with inefficient sorting, the pulp made
from the first load will show a low microscopic count whereas,
unless sorting is exceptionally good, the pulp made from the second
load may show a high count. Thus one batch may readily comply with
the requirements of the Bureau of Chemistry and the next batch may
be outside of those limits. Because of this fact this laboratory
recommends that manufacturers of tomato pulp do not rely upon the
microscopic results of a single sample. The only way in which the
product may be absolutely controlled by means of the microscopic count
is to examine a sample from each batch—that is, from each kettleful or
tankful that is evaporated. This is manifestly impossible. It would
require several analysts for one plant. Moreover, it is entirely
unnecessary.
It has been found that much better results can be secured by having
an analyst in the plant to examine samples from time to time. Then,
whenever the microscopic count becomes excessive, he can locate the
trouble and see that it is corrected.
Manufacturers who desire frequent analyses of their products,
therefore, should employ an analyst and arrange to have him instructed
in a laboratory conversant with the Howard method as used by the
Government. The laboratory of the National Canners’ Association makes
it a practice to give the necessary instruction in this method to
analysts employed by members of the association. These analysts should
be carefully selected. Other things being equal, better results should
be expected of a college graduate or at least one who has had college
training in biology and chemistry. It has been repeatedly demonstrated,
however, that a carefully selected man or woman with common school
education can learn the method and use it with sufficient accuracy for
factory control. The person selected for this work should have good
powers of observation and a positive character.
This laboratory has heretofore advised that manufacturers of tomato
pulp should not give too much attention to the microscopic count of
their product. We have maintained that the expense would be better
placed on the sorting belt; that if the sorting and trimming were
adequately done, the plant maintained in a sanitary condition and the
product manufactured as rapidly as possible, a low microscopic count
would be assured. This we still maintain is true. So many cases have
come to our attention, however, in which canners have not succeeded
in maintaining the degree of sorting necessary with a product of this
kind that we have grown to feel that the presence of an analyst working
continuously in a plant is an additional safeguard.
The conditions attending the canning of tomatoes are widely different
from those attending the manufacture of tomato pulp. The ordinary rot
is almost always apparent from the outside of the tomatoes[3] and is
removed by the peelers when preparing tomatoes for canning. Practically
none of it, therefore, finds its way into the can. With pulp it is
quite different. Any rot which is not removed by sorting and trimming
goes into the cyclone and passes into the pulp. With trimming stock
pulp, the condition is obviously much worse than with whole tomato
pulp. One hundred pounds of tomatoes will yield not far from 85 pounds
of cyclone juice. If only trimming stock is made into pulp, however,
nearly half the tomatoes are used for canning and the remainder (50 or
55 pounds of trimming stock) will only make something like 35 or 40
pounds of cyclone juice. Yet, since the rot is almost entirely on the
outside of the tomatoes, this 35 or 40 pounds made from the trimming
stock contains the same amount of molds as the 85 pounds manufactured
from the whole tomatoes. The mold count of the trimming stock pulp,
therefore, is much higher than that of whole tomato pulp made from the
same raw product.
[3] Tomatoes are sometimes found with rotten centers of which there
is little or no external evidence. This is unusual, however, and
the influence of this form of rot under manufacturing conditions is
negligible.
The Bureau of Chemistry condemns tomato pulp whose microscopic
examination gives results as high as the following figures:
Molds 66 per cent of fields.
Bacteria 100 million per cubic centimeter.
Yeasts and spores 125 per 1/60 cubic millimeter.
These figures, of course, apply to the Howard method as employed by
the Bureau of Chemistry. The method is entirely arbitrary and results
agreeing with those obtained by the Bureau of Chemistry can be obtained
only by using this method substantially as it is used by the bureau.
An examination of the pulp, therefore, by an analyst who is not
thoroughly conversant with this method as it is employed by the Bureau
of Chemistry not only is useless but may actually afford a manufacturer
a false sense of security which will be greatly to his disadvantage.