Ketchup: Methods of Manufacture; Microscopic Examination

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

It is but natural that a product of this kind should vary greatly in flavor due to the selection and quantity of spices, salt, sugar, and vinegar used, and in consistency due to the degree of concentration and fineness with which the base has been comminuted. Most of the recipes for home-made ketchup call for rather liberal spicing and long cooking so that they have a fairly heavy body. These insure good keeping quality, but impart a dark color to the product.

The manufacture of ketchup upon a large commercial scale is of rather recent development and is confined almost wholly to the use of tomatoes as a base. There was little ketchup of the kind best known at present made prior to 1890, as most ketchup was made by what was known as the natural fermentation method, that is, allowing the tomato pulp to ferment spontaneously and using the solid portion for stock. This method was continued, though on a decreasing scale, until 1908, at which time it was practically prohibited. Beginning about 1890, ketchup was made from fresh pulp and barrel stock without fermentation, the fermentation being prevented by the use of a preservative. The method is still in use. The first extensive manufacture of non-preservative ketchup began about 1908, though a few firms had been making it prior to that time, the pioneer probably being E. C. Hazard, of Shrewsbury, New Jersey.

From the amount of space given to the subject of ketchup in the canning and food journals, one might conclude that it is a difficult product to make, or that it is one of very great importance. It is in reality very easy to produce, but has assumed a prominence among food subjects which it does not deserve, due to the fact that some manufacturers have not yet learned the necessity for using care, or persist in using material of questionable quality.

Ketchup is made in the home with very simple apparatus; a colander or sieve for breaking and straining the pulp, and a copper, porcelain, or earthen kettle for cooking, being all that is necessary. The cooking of the tomatoes with the spices, sugar, vinegar, etc., is generally done slowly, until a heavy body is obtained, which results in a dark color, but insures sterility of the product when it goes into the container, and also contributes to keeping quality after it is opened. In the factory many refinements are necessary to make a commercial article which will attract the eye as well as satisfy the sense of taste. The usual dark colored, rough, home-made article will not command a sale over a grocer’s counter alongside of that made in a modern commercial kitchen. Here, sorting tables, washing machine, scalder, cyclone for pulping, steam-jacketed kettle, tanks with coils, or vacuum pan for cooking, finishing machine, bottle washing, and filling machine, are all necessary. The pipes carrying the pulp from one machine or vat to another must be enameled, bronze, tin-lined, or silver-plated to prevent the fruit juice from coming in contact with iron or anything which will cause discoloration. The work is done speedily, and the cooking done in the shortest possible time in order to secure the brightest color and smoothest consistency.

The stock should be whole, sound, ripe tomatoes, preferably grown near the factory so that they may be delivered promptly after picking and with the minimum injury. They should be picked when in prime vine-ripened condition. Fruit picked when just turning and allowed to stand one or two days to color will not have the same rich flavor as when vine-ripened, but will stand rougher handling. Green fruit gives a weak color, and over-ripe fruit is prone to become injured and spoil in handling. The tomato should be through the process of manufacture within twenty-four hours from the time that it is taken from the vine. Repeated experiments have shown that rapid handling of fruits and vegetables gives the best results for canning, and the tomato is no exception to the rule when used for ketchup.

The variety of tomato used is of importance. The tomato will vary in solids from less than 5.5 per cent to nearly 8.75 per cent; in soluble solids from less than 3.5 to nearly 6.5 per cent; in sugar from about 2.25 per cent to 4.25 per cent; and in acidity from .3 per cent to .6 per cent. The colors will vary from an almost creamy white to a very deep red with variations in yellow and purple. The only way to get uniformity in a product is to select one good variety and discard others. The preference is for a clear red smooth tomato of medium size, firm, and of fair acidity. While color may be only “skin deep” as far as being red, yellow, or purple is concerned, experience has shown that a clear red variety gives a better and more lasting color than yellow or purple. A medium sized smooth tomato is preferred because of less adherence of dirt, fewer cracks, and generally more even ripening to the stem. A fairly acid tomato imparts more flavor and needs less vinegar in the finished product. The fleshy portion of the tomato gives the body, but the pulp about the seeds furnishes the characteristic flavor.

The collecting of tomatoes in the field should be done at short intervals so that the fruit may be taken when in prime condition. Where picking is done at too wide intervals, there is a tendency to take fruit that is only colored and not really ripe, and for some to be left and become over-ripe. In both cases the manufacturer is the one to suffer, by increasing the expense of sorting, holding the green if he is to make a high grade product, and by waste from cracking and mashing of the over-ripe. The stems should be left in the field, as they increase the weight and may injure the product to a certain extent.

The handling should be in shallow crates. These should have strong cleats across the ends so that one may be placed above the other without touching the fruit, and if of considerable length, should have a partition. The cleats permit space for ventilation in case they must be stacked for a few hours or more. The depth should be such as not to permit more than three or four layers of fruit. The deep box and the conical basket are not well suited as carriers and should not be used unless delivery can be made by wagon direct from the field and within a few hours after gathering. It is the rule to see cars and barges loaded with baskets arrive at the factory with more or less of the fruit in bad condition. When one basket is set on the edges of two or three others in stacking, there is always cutting of a few of the top fruit, the movement in riding causes others to gradually settle and pack into the cone shape of the bottom, so that if they be held for a day or more, there will be loss of juice, consequent growth of mold, and contamination of the sound fruit from the infected. The actual loss from this form of handling has not been determined, but is undoubtedly much larger than is generally supposed. It is the belief of the writer that the loss is not far from 10 per cent. It is certainly much greater than the difference in the cost of freight and handling of the box over the basket. All baskets and boxes become more or less infected with mold during the season and this spreads to the fruit, the contamination increasing the longer the fruit is held, the tighter it becomes wedged together, or the greater the cracking. The shallow crate affords the better protection.

When tomatoes arrive at the factory, they should be purchased by weight for sound fruit. Buying by the box or basket is antiquated and not satisfactory to either buyer or seller. Under the recent Federal net weight law, purchase by basket or crate must show on each container the exact weight or measure if there be interstate shipment, and the same is true for some of the states. It should not be necessary to give more than a general inspection at the factory. A contract for ripe fruit at ten dollars per ton, which, when delivered, requires sorting, and the holding of unripe and the discarding of defective fruit, is equivalent to ten dollars, plus all the additional cost in labor and the loss in making it fit for use.

If it be necessary to hold the tomatoes for some time at the factory before manufacture, the crates should be stacked in tiers with a foot or more of space between each tier for the circulation of air. Stacking the tomatoes in solid blocks affords the ideal condition for the increase of molds. There can be no doubt that large quantities of fruit have been lost each year from neglect of this simple precaution. Recently a method of holding in water has been originated by Mr. E. W. Grosvenor, at Paoli, Indiana, and consists in using large tanks capable of receiving 500 or more bushels in which tomatoes are submerged in cold water as soon as received, and then held until they can be used. The device is based upon the theory that the tomato skin is practically impervious to water, also that the molds require air for their development and by submergence in water their activity would be lessened.