Ketchup: Methods of Manufacture; Microscopic Examination

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

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.

PULP STOCK.

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.

The use of the specific gravity method only partly solves the question of standardization. Two pulps each of 1.035 may vary considerably in what the chef terms body and there is no method of accurately measuring this factor or expressing it. Pulp made by draining will be lighter in weight with the same body, and that from skins and cores will be rough or have the appearance of separating into small flakes or lumps. The specific gravity bears a close relation to the soluble solids, and as these do not have a constant ratio to the fiber in whole fruit, and as the ratio is further disturbed by drainage and in the use of trimmings, it is obvious that the method will not give an exact standard.

Pulp should be filled into gallon or five gallon cans as hot as possible and sealed at once. The practice followed by some manufacturers is to steam the cans first, then depend upon the heat in the pulp to sterilize. The cans are allowed to stand hot for forty minutes, then cooled. The other practice is to give the hot cans a process of about twenty minutes for gallons, forty minutes for five gallons, and then to cool. Cooling is essential to retain color and flavor, as prolonged heat causes “stack burning,” producing a brownish color and a bitter taste. The highest grade pulp can not be held in barrels for the reason that the heat is retained too long. Stack burning will take place in glass if the packages are not allowed to cool well in the air before being stored, though the changes are not so marked as in the tin.

PULP FROM TRIMMINGS.

The losses in stock from canning tomatoes amounts to about forty per cent. This is due to the unbusiness-like attempt to can all kinds—very large, very small, and wrinkled, which can not be peeled with economy—to wasteful methods of peeling, and to excessive draining of fruit from handling in too thick layers. In this waste there is much that has good food value and which might be worked up into pulp or ketchup stock if properly done. In order to do this, the tomatoes should be sorted so that only those which are in perfect condition for canning will go to the peelers. These should be medium sized, firm, evenly ripened all over, and free from wrinkles. Such tomatoes can be peeled at the minimum of expense and loss. The sound tomatoes which are small, excessively large, wrinkled, or with green butts, can go in with whole tomato stock. The loss in peeling will then be small and can advantageously be discarded. If it be decided to use trimmings from the peeling tables, provision must be made for extra washing, as the ordinary washer removes little more than the coarse dirt and particles, is not sufficient for unusual conditions or to remove tightly-adhering material, and, furthermore, rot must be eliminated before the tomatoes go to the peelers. The writer has never seen a group of one hundred, or any number, of peelers who will stop to trim and separate rot from peels and cores. Trimming can be done better by a few when sorting the tomatoes than at any subsequent step. If clean skins and cores can be had from the peeling table, they can be converted into pulp and sold if labeled properly, “from trimmings.” Whether such waste is suitable for a good product depends upon how it is handled. For the most part, it has not been handled as well as it should be.

The finished pulp made from skins and cores is not the same as that from whole stock. It contains more fiber, remains more or less lumpy, and lacks the smooth body of whole pulp. The color is not so good, and the flavor is likely to be somewhat different. The flavor of the seed cells and that of the fleshy portion of the tomato are different. Pulp made from each part separately shows marked difference, that from the seed cells being poor in color, but with the more characteristic fruit flavor. Tests show that neither part has any true jellying powers, but that the part from the seed cells gives the quality of smoothness, the holding together of the particles of solids. Neither gives a first class pulp alone.

COLOR.

Home-made ketchup generally has a rather dark reddish or brownish color, due to prolonged heating, made necessary under kitchen conditions. At one time this was thought desirable and some of the older recipes call for the use of caramel in order to imitate this color. Most manufacturers now aim to secure a clean, clear color, preferably bright red. This may be obtained when good fruit is used and handled quickly; a muddy brownish or yellowish color is looked upon with suspicion as indicating poor material or defective methods.