BOTTLING.
Only new bottles should be used and these should be thoroughly rinsed before using and preferably with hot water. Since new bottles have no tightly adherent particles on the inside, the use of clear water is sufficient, dependence being placed upon the after process to insure sterilization.
The bottling should be done at as high temperature as is practicable, about 165 to 170 degrees F. If the temperature is higher than this, the possibility of burns in handling is increased, and too much space is left in the neck of the bottle after corking, due to shrinkage of the ketchup on cooling, and if much lower, the expansion in processing causes excessive loosening of caps or corks and breakage. Furthermore, when low temperature is used, it requires a very long time to heat the contents of a bottle in pasteurizing. A ketchup is a very poor conductor of heat and the heavier the body, the longer the time that is required.
The closure may be made with either corks or seals, the recent improvements in the latter making them much safer than they were a few years ago.
PROCESSING.
After the bottles are sealed, they should be given a process to insure sterility, the time being about fifty minutes for half-pints and an hour and fifteen minutes for pints—or sufficient time to insure 190 degrees F. for twenty minutes at the center of the bottle.
This step is omitted by many manufacturers, dependence for sterilization being placed upon washing the bottle and subsequent heating for about twenty minutes. The heating is accomplished by conveying the bottles through a chamber containing numerous steam pipes at high temperature and discharging them at the bottling machine. It is assumed that sterilization of the ketchup has taken place in process of manufacture, and the heat within the bottle will care for any infection which may possibly have taken place at a later time from the cap or cork. The safety of this measure depends upon using a fairly acid ketchup or one with a heavy body. It is a risky procedure for mild or thin ketchup. It is a common occurrence to have the stock keep apparently while in the bottle, but spoil shortly after opening. The spoilage after opening is most often due to forms which have been present since manufacture and only need the presence of air to start growth, and are not due to infection from the air. A ketchup will inhibit the growth of organisms which gain entrance from without, while those which are present but held in abeyance through exclusion of air, will sometimes grow. The writer has samples of ketchup put up in 1906 which apparently are sterile, but which will show spoilage within a few days after opening, though done under sterile conditions, and the spoilage be identical in kind with that observed soon after manufacture. How long these organisms will remain alive is not known. In canning, no foods are considered safe without processing, and the same principle is a good one to follow with ketchup.
Processing may be accomplished in open tanks, in retorts, in specially constructed pasteurizers, such as used in the brewing industry, and in hot chambers, the method is not material, though there may be considerable difference in point of economy.
FACTORY ARRANGEMENTS.
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.