These methods may also be applied to the examination of raw tomatoes
and canned tomatoes. In applying the relations given below to the
results obtained by the examination of tomato pulp or canned tomatoes,
it is assumed that no substance such as sugar or salt has been added.
If salt is found to be present in excess of the amount normal to
tomatoes (from 0.05 to 0.1 per cent), it is necessary to determine the
amount and make correction therefor before applying the relations given
below.
[2] This chapter is largely taken from an article by Bigelow and
Fitzgerald, published in the Journal of Industrial and Engineering
Chemistry. The section on Microscopic Examination is substantially
a reprint of an article by Bigelow and Donk published in the trade
papers in September, 1918. For further information on the analysis of
tomato products the Methods of Analysis of the Association of Official
Agricultural Chemists (1919) should be consulted.
In examining raw tomatoes, care must be taken to secure a
representative sample of the juice. This cannot be done by applying
pressure directly, as the juice of the seed receptacles is of different
composition from that of the fleshy part of the tomato. It is
necessary, therefore, to crush the sample and thoroughly cook it in a
flask surrounded by boiling water and connected with a reflux condenser.