Ketchup: Methods of Manufacture; Microscopic Examination

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

These tanks are made with false bottoms to receive the sand and dirt, are provided with jets to supply fresh water and to cause the tomatoes to automatically feed upon the conveyor. The first impression is that the tomatoes are soaking in rather dirty water, but tests show that they absorb very little, if any, water, and examination at every stage shows them to be washed cleaner than by the usual method. The work has not been carried far enough to be conclusive, nor to indicate its limitations.

Experiments made to duplicate the factory conditions, comparing air and water storage for short periods, were decidedly favorable to the latter. Much less change occurred in water storage for twenty-four to forty-eight hours than in the air, and there was the further advantage that the tomatoes were washed freer from dirt, sand, and mold, and that rot was cut out better under the water sprays. Some lots of tomatoes were held as long as eighty hours, but this is not to be recommended. When rotting does occur under water, it is of a different character from that in the open and is far more offensive.

If tomatoes be accepted at the factory in a mixed condition, that is, greenish, ripe, and over-ripe, they should be passed first over a sorting belt and preferably one which will turn all sides of the fruit to the inspectors. The green fruit should be held out in separate crates to ripen, and the unfit fruit be discarded. If green fruit be not accepted, the inspection can be done better after washing. In any event the fruit must pass slowly on the table and in single layers. No inspection can be made adequate if the tomatoes pile on the belt two or three layers deep, or pass at such a rate that the eyes tire and all look alike. This is a place where more belts moving slowly, and fewer persons working on each belt, will give the better results. Hand sorting is essential and far more important than in tomato canning. In the latter the defective parts are cut away, but no machine has yet been devised to make the separation complete in making pulp or ketchup.

One other point in inspection is the removal of the stems, which should be the duty of the pickers, but which is often neglected. If the ketchup is to have the brightest, cleanest color, the removal of the stem is advantageous and, furthermore, if the tomatoes are raised on sandy ground, there may be enough sand held around the stem to make appreciable grit. Some manufacturers leave the stem on to give flavor.

WASHING.

The washing is the most important mechanical operation in making pulp or ketchup in order to get a clean product. It is the weak spot in most factories, but fortunately is the one that can be most easily changed. The ideal washer is one that first receives the tomatoes in a tank, holding them for a sufficient length of time to soak and to loosen the dirt, and then submits all parts to a thorough spray under strong pressure. Most washers do not meet these requirements. In many cases the tomatoes are either not dropped into water, or go in and then out again so quickly that they are only made wet and bright, but not clean, then pass under a few cross-sprays, each of which does not deliver a stream more than an inch or so in width, the total spraying not being active over a space of more than six inches and only from above. Some machines do not actually spray the fruit more than one or two seconds. In some cases, it is not so much the fault of the machine as that of the owner in over-speeding and over-loading it. Most machines use a sufficient volume of water, but not under sufficient pressure, nor over a sufficient area. One of the best washers in use is a slight modification of the cylindrical washer used for removing the lye and peel from peaches. It consists of a cylinder about two feet in diameter and twelve feet long, made of a specially corrugated iron. The corrugations are sharper than the ordinary pressed metal used for building and siding, and in addition they are perforated at frequent intervals. This cylinder is mounted on a slight incline. The tomatoes are fed in at one end and the revolving motion causes their discharge at the other. The effect of the corrugation is to cause each tomato to turn over and over in its course and thus avoid all sliding. A spray pipe passed through the entire length and, when provided with the proper nozzle, insures a thorough washing, the tomatoes being under actual sprays from six to twenty times as long as in many machines that are now in use. The water pressure should not be less than sixty pounds per square inch and is better above one hundred pounds if fine perforations or nozzles be used. In nearly every case it is necessary to augment the natural pressure by an auxiliary pump. The principle of the strong pressure is seen in using a hose without a nozzle to wash a floor and one with a nozzle and strong pressure. In the former case it does not clean, while with the latter it does and with less water. The washer just described is too vigorous for tomatoes for canning, as the treatment is too rough. If the tomatoes are soft or badly cracked, it causes considerable loss, but not of material that should be used in ketchup. The strong sprays will also cut off adherent mold and soft rot. A thoroughly good washer will do about nine-tenths of the work for the inspectors. During the past season some modifications have been made of this washer in the east. The machine has been enlarged, but better results would be obtained by using a greater number of small ones. Again, some washing machines have been ineffective, not on account of any defect, but because of over-speeding.

The vigor with which the washing is done is always apparent in the finished product. The poor washing usually given to tomatoes for canning, accounts in a measure for the relatively large numbers of organisms found in ketchup made from trimmings.

PULPING.

After washing, the tomatoes may be reduced to a pulp in one of three ways: by running the raw tomatoes directly through a grinder and into the cyclone; by passing the tomatoes through a scalder and into the cyclone; and by turning the tomatoes into jacketed-kettles or tanks and cooking them until soft before running through the cyclone. There is a difference in the product obtained by these methods. The first one gives a somewhat larger yield, as the hard parts are cut and torn so that more will be squeezed through the sieve. The color is generally stronger and inclined to the purple side rather than the yellow. The color, however, does not hold so well when exposed to light. The pulp inclines to froth and there is a marked separation of red pigment on the top. A raw pulp will begin to separate into a clear layer below and solids at the top in about fifteen to twenty minutes after standing in a tank. This is due to the air incorporated in the solids and possibly to difference in specific gravity, and not to fermentation, as frequently alleged. Changes will take place more rapidly in such pulp than in that made from scalded fruit.

There is not a great deal of difference between the second and third methods, the object in both cases being the same. If a long scalder be used, the skins will be loosened and the tissue softened so that it will be easily separated from the green parts, hard cores, or black rot. There will be no acquisition of color from the stems to discolor the ketchup. The loss is a little heavier in scalder heating than where the fruit is cooked in the tanks, but there is the compensation that there is less carrying of hard or objectionable material. A scalder to be effective should be much longer than that used in canning, or a greater volume of steam should be used. The tomatoes should be heated to about 180 deg. F. There is little choice in the two methods, but the preference is with the scalder, both being preferred to the raw ground fruit. A pulp made in this way separates slowly and there will be no material increase in organisms for a rather long time (three or four hours). There is less separation of pigment on cooking and there is a clean look to the tissue under the microscope.