41. WRAPPING AND LABELING.--When the jars of food have stood long enough to cool, usually overnight, they are ready for wrapping and labeling. Wrapping is advisable for practically all foods that are canned, so as to prevent bleaching, and, of course, labeling is necessary when canned food is wrapped, so as to enable it to be distinguished readily when it is in storage. To wrap canned foods, proceed as in Fig. 19. Use ordinary wrapping paper cut to a size that will be suitable for the jar, and secure it in place with a rubber band, as shown, or by pasting the label over the free edge.
PROCEDURE IN THE FRACTIONAL-STERILIZATION METHOD
42. In canning food by the FRACTIONAL-STERILIZATION CANNING METHOD, the procedure is much the same as in the one-period cold-pack method. In fact, the only difference between the two is that blanching and cold-dipping are omitted, and in their stead the food in the jars is subjected to three periods of cooking. When the jars of food are made ready for processing in the sterilizer, they are put in the water bath, boiled for a short time, and then allowed to cool. After 24 hours, they are again boiled for the same length of time and allowed to cool. After another 24 hours, they are subjected to boiling for a third time. Then the jars of food are removed and sealed as in the one-period cold-pack method. By the fractional-sterilization method, the spores of bacteria contained in the food packed in the jars are given a chance to develop during the 24-hour periods after the first and second cookings, those which become active being destroyed by cooking the second and third times. Although some canners prefer this method to those already mentioned, the majority look on it with disfavor, owing to the length of time it requires.
STEAM-PRESSURE METHODS
43. For canning foods by steam pressure, special equipment is necessary. In one of the steam-pressure methods, what is known as a water-seal outfit is required, and in the other a device called a pressure cooker is employed. The work of getting the containers ready, preparing the food for canning, packing it into the jars, and sealing and testing the jars is practically the same in the steam pressure methods as in the cold-pack methods. The difference lies in the cooking and sterilization of the foods after they are in the jars and partly sealed and in the rapidity with which it may be done.
44. CANNING WITH A WATER-SEAL OUTFIT.--A water-seal outfit, which may be purchased in stores that sell canning supplies, consists of a large metal vessel into which fits a perforated metal basket designed to hold jars of food. This vessel is also provided with a tight-fitting cover having an edge that passes down through the water, which is placed in the bottom of the vessel. When heat is applied to the bottom of the vessel, the water inside of it is changed into steam. The cover prevents the steam from passing out, and it collects in and around the metal basket supporting the jars of food. Enough steam is generated in this outfit to raise the temperature about 4 to 6 degrees above the boiling point. Thus, the water-seal outfit will cook the food in the cans in about one-fourth less time than will the water bath of the one-period cold-pack canning method.
45. CANNING WITH A PRESSURE COOKER.--For canning by steam pressure, a number of different kinds of pressure cookers are to be had, but in principle they are all alike and they are always made of heavy material, so as to withstand the severe steam pressure generated in them. In Fig. 20 is shown one type of pressure cooker. It is provided with a bail, or handle, for carrying it and with clamps that hold the cover firmly in place. Attached to the cover is a steam gauge, which indicates the steam pressure inside the cooker, and a pet-cock, which is used to regulate the pressure. On some cookers, a thermometer is also attached to the cover. Also, inside of some, resting on the bottom, is an elevated rack for supporting the jars of food that are to be sterilized and cooked. In operating a pressure cooker, water for generating steam is poured in until it reaches the top of this rack, but it should not be allowed to cover any part of the jars of food. Steam is generated by applying heat to the bottom of the cooker, and the longer the heat is applied the higher the steam pressure will go.