Ketchup: Methods of Manufacture; Microscopic Examination

by A. W. Bitting; K. G. Bitting

In making pulp it is important that the paddles in the cyclone be held back from the screen and the juice driven through by centrifugal force rather than by hard grinding. When kept well back, the green butts, cores, and tissues which have been hardened by brown mold are carried over the end so that there will be fewer black specks in the finished pulp and it will have a better appearance under the microscope.

The pulp should be conveyed immediately from the cyclone to the cooking kettle, and the next operation begun at once. A storage tank is unnecessary when there is large cooking capacity, and in most cases it is a source of trouble rather than a help. A sample should be taken as soon as the batch is drawn, and the specific gravity determined so that the proper quantity may be used to give a finished product of uniform consistency. Assuming that 500 gallons of pulp will give a normal finished batch, if the tomatoes are watery, it may require 550 gallons or more to give the same result when concentrated. This is easily calculated from the specific gravity so that reasonably uniform results may be obtained. Samples should also be tested for acidity once or twice each day so that the addition of vinegar can be governed accordingly. The concentration of pulp will vary from 40 to 60 per cent depending upon its condition and the weight of body desired.

COOKING.

The cooking is done in copper-jacketed kettles, in glass-lined metal, or in wooden tanks, the tanks being heated with coils. The glass-lined tank has the advantage of very little metal coming in contact with the pulp and can be kept cleaner than wood. A question has been raised regarding the suitability of copper for a cooking utensil, though no positive objection has been made. The vacuum pan is coming into use for concentrating pulp, but has been little used in making the finished ketchup. The jacketed-kettle is used by most manufacturers, though the tank and coil is being adopted by those who wish to make large batches, as it is the more economical. Agitators are no longer used, as by proper handling of the steam and automatic traps, little burning occurs on either kettles or coils. The efficiency of the open tank or kettle is increased by providing a strong exhaust or suction for the air at the back and just above the top of the kettle. A swiftly moving current of air across the top of the kettle will carry off the steam and shorten the time of heating from ten to twenty per cent.

A pulp may be reduced in a vacuum pan in about one-fourth the time necessary in the open kettle and with a marked conservation of color and flavor. The vacuum pan may be used for quick reduction and the finish be made in open kettles in order to apply the heat long enough to spice and to sterilize. There are possibilities along these lines which have not been developed.

The time of cooking a batch of ketchup will depend upon the equipment and the consistency of the finished product. With a good kettle or coil and ample steam-supply a batch should be completed in from thirty-five to forty-five minutes. This gives sufficient time to get the most desirable flavor from the spices and is not so long as to result in discoloration.

SEASONING.

The selection of the spices depends entirely upon the flavor desired. Cinnamon, cassia, cloves, allspice, mace, pepper, paprika, cayenne pepper, mustard, ginger, coriander, bay leaves, caraway and celery seed, are all to be found in the various formulae. Some manufacturers spice lightly in order to retain the maximum of the base flavor, while others go to the opposite extreme on the misguided assumption that they will act as preservatives. The quantity used should be determined by the flavor desired and upon no other consideration. The spices may be used whole, ground, or in some cases as acetic acid or oil extracts. The whole spices are preferred by nearly all the manufacturers of high grade goods. They are more expensive, but give a different flavor from the extracts. The spices are weighed for each batch and are tied in a bag or placed in a wire basket and suspended in the kettle while cooking. Some use very large quantities and cook from only ten to twelve minutes in order to get a distinctive flavor. This is very expensive, as only a small quantity of the flavoring matter is extracted in such a short time. One of the serious objections to the use of the whole spices is that they may darken the ketchup and also cause some discoloration in the neck of the bottle. For that reason, black pepper and allspice in particular are being discarded, and oil of cloves is being used in part for the whole berries. The grade of the spice will also have an effect, the cheap stock being unsuitable for a bright clean product. Small quantities of ground cayenne pepper are used as a substitute for the black pepper.

Acetic acid extracts of some of the spices are being used to a certain extent, but they have a peculiar harsh flavor that makes them undesirable. The oil extracts can be used to only a very limited extent, as they impart a flavor suggestive of the drug store.

One method of making a nearly complete extraction of the spices is to place them in their proper proportion in vinegar a few weeks before the ketchup season begins and then add the spiced vinegar in the proper proportion to each batch. The result is different from that obtained by cooking, and the method is not recommended for first grade goods.