We will say that we have found out that 20 degrees on the hydrometer is the proper point at which to add the flour mixture—that this degree of thickness, with the added thickness produced by the flour mixture, produces a soup, which when cold and well shaken, will be thick enough, but will also pour out of the can easily and smoothly. We test the boiling liquid several times; it runs 14 degrees, then after a few minutes 18 degrees, then 20, and it is time to add the flour.
Adding Flour
The flour must be smoothly mixed with water in a flour mixer with sifter attachment. For a 100 gallon batch of soup I would recommend 40 lbs. of hard flour and 13 gallons of water. The hard flour seems to give the best results. The water is placed in the bottom of the mixer and the mixing attachments (paddles and sifter) set in motion either by a separate motor or by a belt from a line of shaft. The flour is then poured through the revolving sifter and is brushed through as a fine powder, which the paddles slowly work into the water without allowing lumps to form. When the total amount of flour is added to the water, and the paddles have worked the mixture up smooth, the flour mixture is added to the boiling contents of the kettle, either in pails or by means of enamel lined pipe running from the mixer to the cooking kettles. The contents of the kettle should be at a vigorous boil when the flour is added, and the flour mixture should not be thrown in so fast that it will kill the boil. During this process the boiling mass should be stirred vigorously with a long paddle. After all the flour is in the kettle the boil is continued for ten minutes, after which time the batch of soup is done and ready to be let down into the finishing machine.
Filling and Processing
From the finisher it is conducted to a receiving tank, and thence to the filling machine. A large volume of soup should not be kept ahead in the receiving tank as it cools and may get somewhat lumpy. The hotter it is canned, the better, and it should be placed in the process tanks immediately after canning.
It is usually canned in No. 1, 16 oz., and No. 10 cans, and is filled with a rotary filling machine of the type used for heavy liquids.
It may be processed either in straight process tanks or in a continuous agitating pasteurizer. If the straight stationary tanks are used the following time is given in boiling water: No. 1, 30 minutes; 16 oz., 40 minutes; No. 10, 1 hour. If a continuous agitating pasteurizer is used this time can be cut down about 60%.
As soon as the processing is completed the cans should be gradually cooled in cold water and left in the cold water until the outside has cooled sufficiently to allow them to be handled easily. On account of the flour it contains soup holds its heat a long time, and it should be properly cooled before stacking away.
Shaking and Labeling
Before shaking and labeling it is wise to let the soup stand for about ten days, both to give leaks a chance to show up, and to give the contents of the can a chance to thoroughly “set.” If the soup is shaken too soon after it is canned there is a possibility of it coagulating again, but this will be avoided if the soup is allowed to stand long enough before shaking—10 days being ample.