The making of ketchup is simple and the factory arrangement for doing the work should be as compact as possible, so that after the pulp is once heated, there is an advantage in having the various steps follow in succession by gravity rather than be conveyed by pumps, especially in small plants. The piping should be as short and direct as possible. The machinery for filling bottles, corking, etc., leaves much to be desired; as separate units they work fairly well, but there needs to be some method devised for handling the bottles automatically from the time they are placed on the washer until they are labeled, ready for the box. At present the time between turning the crate of tomatoes upon the sorting belt until it is ready for the box is only slightly over two hours. Further improvement will not be so much in shortening the time as in eliminating the hand labor.
The foregoing description applies to the making of unfermented, non-preservative ketchup, made from sound stock and delivered into the bottle. Very little ketchup, comparatively speaking, is sold to the consumer in any package other than the bottle. It can be delivered into the bottle when first made, at less expense for labor, with less fuel, and with distinctly less waste than at any subsequent time. It will have a better color and consistency than if stored in bulk and bottled later. It is, therefore, advisable to bottle as much as possible at the time it is made. Ketchup may be packed in bulk in jugs, tin cans, and in barrels, but not satisfactorily; the jug is a poor package; the enamel may be dissolved off the tin can and pinholes form; and the barrel always gives a poor color and off flavor. The best container for bulk ketchup is the gallon glass bottle.
During the height of the season, it may not be possible to convert all the tomatoes directly into ketchup, in which event the surplus may be made into pulp. The first part of the operation is identical with that already described. The concentration is carried just far enough so that subsequently by slow heating for spicing it will give the proper consistency when made into ketchup. A standard has not been fixed, but tentatively it has been proposed that it be at about a specific gravity of 1.035. The concentration may be carried further and water added at the time of the final cooking, but when this is done, the resultant product does not have the same smooth consistency that is obtained by using the thinner pulp. Heavy pulp is made for the purpose of economizing in cans, but experience has shown that economy does not always follow. The higher the concentration, the higher the acid content, and this may attack the enamel and metal with resulting bitter flavor and frequent pinholes. Some manufacturers who prepare their own pulp carry the concentration between 1.030 and 1.033. The method of obtaining this density is to use flasks graduated to hold 500 or 1000 grams of water at 200 degrees F., fill them with the hot pulp and weigh at once. For each flask there should be a proper counterpoise, and the balance be sensitive and weigh in grams. If the 1000-gram flask be used, the specific gravity will be the same as the weight of the pulp. With a valve funnel the flask may be filled level full and the weight taken in less than thirty seconds. For cold pulp, a similar flask is used, but graduated at 60 degrees F. and after filling, the flask is set in a sling and whirled a few times to free it from bubbles, filled again to the level, and then weighed. For pulp of a specific gravity of less than 1.037, this gives fairly concordant results, but the errors increase rapidly the higher the concentration. The same methods may be employed on ketchup. Recently, W. D. Bigelow has improved the apparatus by using a copper flask and adding a handle by which the flask may be submerged in the kettle to take the sample and thus prevents the entrance of air. The use of flasks of any size is described in Bulletin No. 3, National Canners’ Association.