Soup should not be heavily spiced, as many people do not like highly seasoned soups, and if it isn’t hot enough for some consumers they can add as much pepper as they want to. So far as I know the spices most commonly used are white pepper, paprika, cassia, mace, cloves, bay leaves, and celery salt. Black pepper should not be used at it makes black specks in the soup which are apt to be mistaken for dirt. About 7 oz. of white pepper to 100 gallons of finished soup will give it sufficient spiciness. If paprika is used this can be cut down somewhat. Cassia, mace or cloves are used in small amount, 1 oz. of either being ample.
Pepper, cloves, and cassia are added at the beginning of the cooking and mace is added just a few minutes before the flour. It is said that celery salt gives tomato soup a very nice flavor but I have never tried it. Some people like bay leaves, but I have tasted canned tomato soup with a very decided bay leaf taste which I thought was about as poor as any soup I have ever tasted.
The onions are chopped the same as for catsup, and 4 lbs. is about the right amount for 100 gallons of soup.
Sugar and Salt
The sugar can be added at any time after the spices, butter, and onions, but about 5 lbs. should be held back from the average amount being used, figuring that we are cooking a 100 gallon batch, and after the sugar and salt is in, the contents of the kettle should be tasted before the balance of the sugar is added. It may be that the last 5 lbs. are not needed, or it may be that all of it is needed and also an additional 5 lbs. For fresh tomatoes about 25 or 30 lbs. of sugar may be sufficient for a 100 gallon batch, and for pulp it may be necessary to use as much as 50 lbs. or even 60 lbs. in some cases.
After the condensation has continued until the boiling mass is of the consistency of thin pulp the salt is added. The same grade of salt is used as for catsup, and about 14 lbs. is the right amount. The sugar and salt should be put in small containers or pails and scattered slowly over the surface of the boiling pulp.
Testing Thickness Before Adding Flour
Now the contents of the kettle contain all of the ingredients except the flour and the water which is mixed with the flour when it is added. Before this flour mixture is added the contents of the kettle must be condensed to a definite thickness. If this thickness is not measured with a fair degree of accuracy the finished soup will either be so thick that it will be lumpy in the can, even after shaking, or it will be so thin that the housewife is apt to feel that she is getting cheated when she pours the soup out of the can. The object to attain should be to have the soup as thick as the consumer could reasonably expect, but at the same time to have it of such consistency that it will pour out of the can easily and smoothly. Nobody wants soup that will come out of the can like a brick, but at the same time they expect condensed soup to be reasonably thick.
I prefer to gauge the point at which it is time for the flour to be added with a hydrometer. The use of the hydrometer here is subject to the same precautions as were described under the testing of pulp, and it is used in the same way. Whatever reading pulp of specific gravity 1.04 gives on the hydrometer you use, that is the reading you should take for the point at which to add the flour mixture on soup. If you follow this rule you will come out all right. We will say that pulp of the degree of fineness you have reads twenty degrees on your hydrometer when it is at a specific gravity of 1.04. Then twenty degrees on this hydrometer is the point at which the flour mixture should be added on soup.
It might occur to you that it would be a good idea to use the specific gravity test by weighing to determine the point at which to add the flour. This would work all right if you used the same amount of sugar all the time, but as varying quantities of sugar will vary the specific gravity without materially varying the thickness of the pulp, using the specific gravity test by weighing at this point is apt to throw you off. This varying amount of sugar will have a slight effect on the hydrometer reading also, but not enough to make an appreciable difference. What you really want is to have your partially completed soup at a uniform thickness before adding the flour, rather than at a uniform specific gravity. Thickness and specific gravity do not always correspond. Tomato fiber may be very thick and still have a rather low specific gravity, and it may be thin and have a high specific gravity due to the fact that it contains added sugar in solution. For determining the point which we are trying to gauge, the hydrometer is much less apt to throw you off the track than is a specific gravity test by weighing, as increasing thickness will change the hydrometer reading very quickly but will only alter the specific gravity slowly.