Thursday, April 19, 2012

Canning and Drying Part 6: Packing and Waterbath Processing

THE COLD-PACKING METHOD
1)      Prepare the jars. Boil and sterilize them as well as the lids. They should be kept warm so that they do not crack in the water bath. Keeping the lids warm will soften the rubber and make sealing more effection.
2)      The food to the canned should be clean. You must decide it you will can them whole or cut. The recommended procedure for different kinds of produce will be discussed later. 
3)      Scald or blanch the fruit if necessary. Blanching tomatoes, prunes, and plums will loosen their skin, making them easy to peel off. Ripe fruits must be scalded very quickly so that they do not become soft. They should never remain in the water after the skin has loosened. A wire basket or a cheesecloth will contain the fruits as you dip them in the boiling hot
a.       Blanching reduces the bulk of spinach and other greens. It also improves their flavor and partially sterilizes them.
b.      To blanch, bring a pot of water to a boil. Use a wire colander to immerse the food in the boiling water, or suspend the food over the boiling water to steam it. The entire boiling-water and suspended food contraption should be covered by a lid to enclose the steam. 
c.       Blanch or steam as long as necessary - to reduce the bulk of the food, remove the skins, etc.
4)      Cold-dipping
a.       Improves color
b.      Stops softening/cooking process, making food firm and easy to handle,
c.       Loosens skin
d.      Shocks and destroys bacteria spores
e.       To cold-dip, plunge scalded, blanched, or steamed food into cold water, then remove at one.
5)      Pack the jars immediately and rapidly. Arrange the jars in order and use a spoon to fill each with the fruit/vegetable. They should be filled solidly, so as to put more food in each jar.
6)      Fill the jar with boiling hot liquid, either plain water, salt water, pickling liquid, or syrup depending on the food. Some tomatoes and greens need not have any liquid added as they will produce their own. The jars should be about half an inch from the top to leave some room for the food to boil while processing in the water bath.
7)      Prepare for the water bath processing by wiping the jar rims well. Place the jar covering and seal it.

THE WATER BATH METHOD
1)      Fill a large vessel of water to a boil, tall enough to cover the jars with 2 inches of water. A tall stock pot or pressure cooker pot is excellent. 
2)      A thick folded kitchen towel or rack should be placed at the bottom of the vessel so that jars do not sit directly on the bottom of the pot. They will crack if this is not done.
3)      Bring the water to a boil while you fill the jars with food.
4)      Make sure the jars are warm and not cold. If they are cold, warm them up in some hot water before lowering into the water-bath.
5)      Lower the jars in the water using a pair of jar lifters. Make sure the jars are covered by 2 inches of water, adding water if necessary. The jars should be upright and again, resting on a rack or cloth in the bottom.
a.       Perhaps your pot has a basket for arranging the jars in a basket and lowering them into the water all at once.
6)      Cover the pot with a good lid. Bring the water to a boil and process the jars for the prescribed time. Set your timer from the time the water begins to bubble violently. Use a kitchen timer or alarm clock. The boiling water will cook and sterilize the food in the jars.
When the jars are in place, put the tight-fitting cover on the sterilizer and allow the water to boil and thus cook and sterilize the food in the jars. The length of time for boiling varies with the kind of food and is given later with the directions for canning different foods. The boiling time should be counted from the instant the water in the sterilizer begins to bubble violently. A good plan to follow, provided an alarm clock is at hand, it to set it at this time, so that it will go off when the jars are to be removed from the sterilizer. Sit the jars on the countertop for 12-24 hours and check the seal, making sure that it is firm.
7)  Now label your jars with a sticker or a permanent marker, noting the date, batch, and contents.



Canning and Drying Part 7: Directions for Canning Vegetables

(From the Women’s Institute Library of Cookery 1925)


DIRECTIONS FOR CANNING VEGETABLES

56. CLASSIFICATION OF VEGETABLES.--To simplify the directions here given for the canning of vegetables, this food is divided into four groups, as follows:

1. Greens, which include all wild and cultivated edible greens, such as beet greens, collards, cress, dandelion, endive, horseradish greens, kale, mustard greens, spinach, New Zealand spinach, and Swiss chard.

2. Pod and related vegetables, which include asparagus, beans, both string and wax, Brussels sprouts, cabbage, cauliflower, eggplant, okra, peppers, both green and ripe, summer squash, and vegetable marrow.

3. Root and tuber vegetables, which include beets, carrots, kohlrabi, parsnips, rutabagas, salsify, sweet potatoes, and turnips.

4. Special vegetables, which include beans, both Lima and shell, corn, mushrooms, peas, pumpkin, sauerkraut, squash, succotash and other vegetable combinations, and tomatoes.

The convenience of this plan will be readily seen when it is understood that, with the exception of the special vegetables, the same method of preparation and the time given for the various steps in the canning process apply to all vegetables of the same class. Thus, if directions for a vegetable belonging to a certain class are not definitely stated in the text, it may be taken for granted that this vegetable may be canned in the manner given for another vegetable of the same class.


57. GENERAL DIRECTIONS.--The canning of vegetables may be most successfully done by the one-period cold-pack method. Tomatoes, however, because of the large quantity of acid they contain, may be canned and kept with little difficulty by the open-kettle method, but they will be found to keep their shape better if the cold-pack method is employed.
The time required for cooking any vegetable after it is packed in jars depends on the kind and the age. Therefore, if a vegetable is hard or likely to be tough, it may be necessary to increase the time given in the directions; whereas, if it is young and tender or very ripe, as in the case of tomatoes, the time for cooking may perhaps have to be decreased. Because, in altitudes higher than sea level, the boiling point of water is lower than 212 degrees Fahrenheit, the length of time for boiling foods in the water bath must be increased after an altitude of 500 feet is reached. Therefore, for every additional 500 feet over the first 500 feet, 10 per cent. should be added to the time given for the boiling in water. In case a pressure cooker is used, however, this is not necessary.
The canning directions here given are for 1-quart jars. If pint jars are to be used, decrease the salt proportionately; also, decrease the time for cooking in each case one-fifth of the time, or 20 per cent. If 2-quart jars are to be used, double the amount of salt and add to the length of time for cooking one-fifth, or 20 per cent. For instance, if a 1-quart jar of food requires 90 minutes, a pint jar of the same food would require 72 minutes and a 2-quart jar, 108 minutes.



 

Canning and Drying Part 5: Preparation

(From the Women’s Institute Library of Cookery 1925)

PREPARATION FOR CANNING

53. In canning, as in all other tasks related to cookery, the housewife's aim should be to do the greatest amount of work, and do it well, with the least effort on her part. The results she gets in canning, then, will depend considerably on the orderly arrangement of the utensils and materials with which she is to do the work. But of greater importance is the preparation she makes to eliminate as much as she can the possibilities of contamination, for, as has been repeatedly pointed out, success in canning depends on the absence of dangerous bacteria.




54. From what has just been mentioned, it is essential that everything about the person who is to do the work and the place in which the work is to done should be clean. Clean dresses and aprons should be worn, and the hands and finger nails should be scrupulously clean. The kitchen floor should be scrubbed and the furniture dusted with a damp cloth. Any unnecessary utensils and kitchen equipment should be put out of the way and those required for canning assembled and made ready for the work. The jars should be washed and the covers tested by fitting them on without the rubbers. If a glass cover rocks, it does not fit correctly; and if a screw cover will not screw down tight, it should be discarded. Without the rubber, there should be just enough space between the cover and the jar to permit the thumb nail to be inserted as is shown in Fig. 3. The edge of each jar and each glass cover should be carefully examined every time it is used, so that none with pieces chipped off will be used, as these will admit air. This examination is made by running the finger over the edge of the jar and the cover, as is shown in Fig. 4. The jars, covers, and rubbers should be put into pans of cold water, and the water should be brought to the boiling point and allowed to boil for 15 minutes or more while the fruit or vegetables are being prepared for canning. They should be kept in the hot water until the food is ready to be placed in them. In the one-period cold-pack method, it is not necessary to boil the jars, rubbers, and covers, but this may be done if desired.


To produce good-looking jars of food, the fruit or vegetables to be canned should be graded to some extent; that is, the finest of the fruits or vegetables should be separated and used by themselves, as should also those of medium quality. Often it is wise to use the poorest foods for purposes other than canning. The food may then be canned according to the chosen method, but by no means should methods be mixed. In handling the product after it has been cooked by the open-kettle method, any spoon, funnel, or other utensil must be thoroughly sterilized in the same way as the jars and their covers and rubbers; indeed, no unsterile utensil should ever be allowed to touch the food when a jar is being filled.
55. It is by the observance of such precautions as these, some of them seemingly unimportant, that the housewife will be repaid for her efforts in canning and be able to produce canned fruits and vegetables like those shown in color in Fig. 22. This illustration shows, with a few exceptions, such foods canned by the one-period cold-pack method, and merits close inspection. As will be observed, the jars are full and well packed and the color of each food is retained. Each can of food indicates careful work and serves to show the housewife what she may expect if she performs her work under the right conditions and in the right way. This illustration likewise serves to demonstrate that any food may be successfully canned by the one-period cold-pack method, a claim that cannot be made for the other canning methods. In fact, some of the foods illustrated, as, for instance, peas and corn, cannot be canned successfully by any other method.

Canning and Drying Part 4 - Methods of Processing

(From the Women’s Institute Library of Cookery 1925)
Methods of Processing:
Canning Methods can be broken down into two steps:
1)      The Preparation of the food to be canned – sterilizing the jars and lids, preparing the food,  filling the jars, and covering them.
2)      The Processing of the jars to be sealed – whether by pressure or water-bath

Open Kettle Method Processing
In the old days, housewives began preserving food using the open-kettle method.
·         Preferred method of canning during the late 19th and early 20th Centuries
·         Requires on minimal, common, equipment
·         Cooking the food to be canned, transferring it into jars, and sealing the jars
·         Does not process the jars, but uses heat from the food to seal the jars
·         Exposure of food without sterilization, liable to contamination between cooking and filling the jars.
·         Danger of contaminating contents before the jar is closed and sealed – mortally dangerous botulism poisoning because botulism spores are pervasive in the air.
·         No longer used, considered to be unsafe

Equipment (All utensils touching the food must be sterilized):
1)      Large enamel  or  metal saucepan to cook food
2)      Measuring utensils
3)      Large pot to sterilizing jars, rubbers, and lids,
4)      Large spoons
5)      Knife

Procedure:
1)      Sterilize jars, rubbers, and lids. Wash them thoroughly and boil them in clear water for 15-20 minutes
2)      The food to be canned should be picked over, with bruised, damaged, and decayed parts, removed. Seeds, leaves, roots, stems, etc. should be removed too. Then the food should be washed free of dirt and grime.
3)      Cook the food. Fruit is usually prepared with syrup until softened. Vegetables are usually cooked with salt and water until soft.
4)      Transfer the food to sterile jars, filling them well, and seal them with the jar lids and rubbers. Invert the jar for the food to cool and the jar to seal properly. Make sure it has sealed, and does not leak.

Oven Processing
·         Jars are sterilized and filled with food, placed in a pan of shallow water in the slightly warm oven. The jars with the food in them are not sealed but the jar lids without the rubber seal is placed on loosely. The oven temperature is raised until the water in the pans boil and then baked for another 30-45 minutes. After the food is cooked in the oven, the jars are removed, filled to be brim with boiling water or syrup, and sealed tightly.
·         Similar to the open-kettle method, also subject to serious contamination but slightly less dangerous.
·         May be difficult and dangerous to handle hot jars in the oven

Water Bath Processing
·         Water bath processing is sterilized the filled jars of food in a large stock pot covered by 1-2 inches for water for a time, so that the interior temperature of the jar is raised and unwanted dangerous bacterial spores are eliminated.
·         Today, water-bath canning, though safer than open-kettle processing, is generally discouraged by professionals in the food safety industry especially with regards to low-acid foods, because the temperature during processing cannot be high enough to completely eliminate bacterial spores. A large concentration of acids in certain foods contributes to the elimination of bacterial spores and are thus (still) condoned (but not encouraged) by food safety experts.
·         The Amish have been canning foods using the waterbath method for generations just like all housewives in the early 20th did. They suffer no ill-consequence because of their simple meticulous hygiene. They do not follow modern fads and advise of modern “professionals” but keep doing things the old way. Their simple values include disposing of any canned food that is questionable, such as food with the lids unsealed or with a bad odor. If you are careful, the water-bath method can work. This is a decision you have to make for yourself. Take care to learn from someone who still follows the old ways and can help you. Do not take risks if you are ignorant.

Pressure Cooker Processing
·         Pressure canning is by far the most efficient way to can food if you have the proper equipment. It heats food using pressure, and thus saves on gas/coal heating because it uses steam pressure. It also saves cooking time, because it heats and sterilizes food to higher temperatures in a quarter of the time compared to water-bath canning. It produces the safest and most sterile food of all the methods.
·         You need the proper processing equipment to do pressure-cooker canning. You need a tall, sturdy, and safe pressure cooker. You also need new, strong jars without blemishes like chips that can withstand pressure. You need jars specifically made for canning, like Ball’s. These jars can be reused, but you cannot reuse mayonnaise or tomato sauce jars any more for pressure canning as they will crack under the heart.
·         The preparation and sterilizing of the food and jars for pressure-cooker processing is exactly the same as the water-bath method. 



Wednesday, April 11, 2012

Canning and Drying Part 3 - Equipment

 You will find that among the Amish and Mennonites there still exists the same frugal methods of food preservation that were an institution among all mothers and grandmothers in the early 20th century. It is regrettable that the household skills of the past have been almost completely rendered extinct by our crippling reliance on commercialized food. It is time that these skills be revived in the home. This following excellent exposition on the canning and drying of food is so simple and comprehensive that there is no need for the editor to further elaborate. Such as a text as this is an excellent starting point for daughters and mothers to begin the study and practice of canning and drying in the home.
(From the Women’s Institute Library of Cookery 1925)

GENERAL EQUIPMENT FOR CANNING

15. The equipment required for canning depends on two things: the quantity of food to be canned at one time and, since there are several canning methods in use, the canning method that is to be employed.

Various kinds of elaborate equipment have been devised to make the work of canning easy as well as effective. However, it is possible to do excellent work with simple equipment, and if the matter of expense must be considered there should be no hesitation about choosing the simplest and least expensive and doing the work in the best possible way with it. It is important also that utensils already included in the household equipment be improvised to meet the needs of the canning season as far as possible.

16. Whatever the canning method that is to be followed may be, there are a number of utensils and containers that go to make up the general equipment that is required. Familiarity with such an equipment is extremely necessary for correct results in canning, and for this reason the general equipment is discussed here in detail. The special equipment needed for each of the canning methods, however, is not taken up until the method is considered. In giving this general equipment, mention is made of some utensils that are convenient but not absolutely necessary. Any unnecessary, but convenient, part of a canning equipment should therefore be chosen with a view to its labor-saving qualities and its expense. A device that will make the keeping of canned foods more certain and prevent loss may be a valuable purchase; still, that which makes for greater convenience, but not absolute saving, need not be considered a necessity.

17. VESSELS FOR CANNING.--The pots, kettles, and pans in ordinary use in the kitchen for cooking purposes are usually satisfactory for the canning of foods. Those made of tin or iron, however, are not so good as enameled ones or those made of other metals, such as aluminum. Especially is this true of utensils used for the canning of acid fruits or vegetables, because, if such food remains in contact with tin or iron for more than a few minutes, the acid will corrode the surface sufficiently to give the food a bad or metallic taste. In addition, such utensils often give the food a dark color. If enameled kettles are used for the cooking of foods that are to be canned, it is important that the surface be perfectly smooth and unbroken. Otherwise, it will be difficult to prevent burning; besides, chips of the enamel are liable to get into the food. Kettles for the cooking of fruits with sirup should be flat and have a broad surface. Fruit is not so likely to crush in such kettles as in kettles that are deep and have a small surface.

18. KNIVES, SPOONS AND OTHER SMALL UTENSILS.--Many of the small utensils in a kitchen equipment are practically indispensable for canning purposes. Thus, for paring fruits and vegetables and cutting out cores, blossoms, and stem ends or any defective spots, nothing is more satisfactory than a sharp paring knife with a good point. For paring acid fruits, though, a plated knife is not so likely to cause discoloring as a common steel knife. There are, however, other useful implements for special work, such as the strawberry huller, Fig. 1, for removing the stems of strawberries, and the peach pitter, Fig. 2,  
 for removing the stones from clingstone peaches. For placing the food to be canned into jars, both forks and large spoons are necessities. A large spoon with holes or slits in the bowl is convenient for picking fruits and vegetables out of a kettle when no liquid is desired, as well as for skimming a kettle of fruit. For packing foods into jars, a long-handled spoon with a small bowl is convenient. Still another useful small utensil is a short, wide funnel that may be inserted into the mouth of a jar and thus permit the food to be dipped or poured into it without being spilled.
19. DEVICES FOR MEASURING.--Accurate measures are necessary in canning; in fact, some of the work cannot be done satisfactorily without them. A half-pint measuring cup and a quart measure with the cups marked on it are very satisfactory for making all measures.
Scales are often convenient, too. For measuring dry materials, they are always more accurate than measures. Many canning proportions and recipes call for the measurement of the ingredients by weight rather than by measure. When this is the case and a pair of scales is not convenient, it is almost impossible to be certain that the proportions are correct. For instance, if a recipe calls for a pound of sugar and an equal amount of fruit, a measuring cup will in no way indicate the correct quantity.
20. COLANDER AND WIRE STRAINER.--For the cleansing of fruits and vegetables that are to be canned, a colander is of great assistance; also, if a large wire strainer is purchased, it may be used as a sieve and for scalding and blanching, steps in canning that are explained later.
21. GLASS JARS.--For household canning, the most acceptable containers for food are glass jars that may be closed air-tight with jar rubbers and tops. Use is sometimes made of bottles, jars, and cans of various kinds that happen to be at hand, but never should they be employed unless they can be fitted with covers and made positively air-tight. Like utensils, the glass jars that are a part of the household supply should be used from year to year, if possible, but not at the loss of material. Such loss, however, will depend on the proper sealing of the jars, provided everything up to that point has been correctly done. All jars should be carefully inspected before they are used, because imperfect or broken edges are often responsible for the spoiling of food.
In purchasing glass jars, only what are known as first quality should be selected. Cheap jars are likely to be seconds and will not prove so satisfactory. Glass jars may be purchased in sizes that hold from 1/2 pint to 2 quarts. If possible, food should be canned in the size of jar that best suits the number of persons to be served.
If the family consists of two, pint jars will hold even more than may be used at one time, while if the family is large the contents of a quart jar may not be sufficient.

22. Numerous types of glass jars are to be had. Some of them are more convenient than others and may be made air-tight more easily. These two features are the most important to consider in making a selection. Jars that close with difficulty, especially if the tops screw on, are not likely to keep food successfully because the bacteria in the air will have a chance to enter and thus cause the food to spoil.
Glass jars used for canning foods have improved with canning methods. The old-style jars had a groove into which the cover fit, and melted sealing wax or rosin was poured into the space surrounding the cover. Later came the screw-top jar shown in Fig. 3. This type of jar has been extensively used with excellent results. Both the mouth of this jar and the jar top, which is made of metal, usually zinc, lined with glass or porcelain, have threads that match, and the jar is sealed by placing the jar rubber over the top, or ridge, of the jar and then screwing the jar top firmly in place. Such jars, however, are more difficult to make air-tight than some of the newer types. One of these jars is illustrated in Fig. 4. It is provided with a glass cover that fits on the ridge of the jar and a metal clasp that serves to hold the cover in place and to make the jar air-tight after a rubber is placed in position. Another convenient and simple type of glass jar, known as the automatic seal top, has a metal cover with a rubber attached.
Another improvement in jars is that the opening has been enlarged so that large fruits and vegetables, such as peaches, tomatoes, etc., can be packed into them whole. With such wide-mouthed jars, it is easier to pack the contents in an orderly manner and thus improve the appearance of the product. Besides, it is a simpler matter to clean such a jar than one that has a small opening.

23. JAR TOPS AND COVERS.--While the tops, or covers, for glass jars are made of both metal and glass, as has been stated, the glass tops meet with most favor. Of course, they are breakable, but they are even more durable than metal tops, which are usually rendered less effective by the bending they undergo when they are removed from the jar. Covers made of zinc are being rapidly abandoned, and it has been proved that the fewer the grooves and the simpler the cover, the more carefully and successfully can it be cleaned. For safety, glass tops that have become chipped or nicked on the edges that fit the jar should be replaced by perfect ones. The covers for automatic-seal jars must be pierced before they can be removed, and this necessitates a new supply for each canning. If there is any question about the first-class condition of jar covers, whether of metal or glass, tops that are perfect should be provided.


24. JAR RUBBERS.--Jar rubbers are required with jar tops to seal jars air-tight. Before they are used, they should be tested in the manner shown in Fig. 5. Good jar rubbers will return to their original shape after being stretched. Such rubbers should be rather soft and elastic, and they should fit the jars perfectly and lie down flat when adjusted. A new supply of rubbers should be purchased each canning season, because rubber deteriorates as it grows old. Rubbers of good quality will stand boiling for 5 hours without being affected, but when they have become stiff and hard from age it is sometimes impossible to make jars air-tight. Occasionally, two old rubbers that are comparatively soft may be used in place of a new one, and sometimes old rubbers are dipped in paraffin and then used. However, if there is any difficulty in sealing jars properly with rubbers so treated, they should be discarded and good ones used.



25. TIN CANS.--For household canning, tin cans are not so convenient as glass jars, but in spite of this they are coming into extensive use. The kind that may be used without any special equipment has a tin lid that fits into a groove and is fastened in place with rosin or sealing wax. Some cans, however, require that the lids be soldered in place. While soldering requires special equipment, this method of making the cans air-tight is the best, and it is employed where considerable canning is done, as by canning clubs or commercial canners.
In the purchase of tin cans, the size of the opening should receive consideration. If large fruits and vegetables, such as peaches, pears, and tomatoes, are to be canned, the opening must be a large one; whereas, if peas, beans, corn, and other small vegetables or fruits are to be canned, cans having a smaller opening may be chosen. When acid fruits or vegetables are to be canned, use should be made of cans that are coated with shellac, as this covering on the inside of the cans prevents any action of the acid on the tin.



For modern usage, these are the kind of jars available:

1) Ball's and other companies produce canning jars with screw lids. These are made of thick, good, glass and can be pressure-canned. The lids, however, are not completely reusable. They come in many sizes with both wide and narrow mouths.
Ordinary Mouth Ball Jars



Wide Mouth Ball Jars
2) Tattler produces plastic lids and rubber rings that are reusable with a lifetime warranty. They are excellent in quality and very practical. 

3) Gasket jars have metal clasps and a rubber seal with tabs. They are used widely in Europe, but are not preferred in North America because unlike the screw-top jars, they do not "pop" when sealed and  unsealed, making it difficult to determine if it has been sealed properly.




 4) Tin cans are now only used for commercial production. They are not used in home canning.

5) Also, many brilliant and useful tools have been invented in recent years for use in the kitchen, such as pineapple peelers. Modern kitchen equipment can also be useful in canning.

Canning and Drying Part 2 - Principles of Canning

 You will find that among the Amish and Mennonites there still exists the same frugal methods of food preservation that were an institution among all mothers and grandmothers in the early 20th century. It is regrettable that the household skills of the past have been almost completely rendered extinct by our crippling reliance on commercialized food. It is time that these skills be revived in the home. This following excellent exposition on the canning and drying of food is so simple and comprehensive that there is no need for the editor to further elaborate. Such as a text as this is an excellent starting point for daughters and mothers to begin the study and practice of canning and drying in the home.
(From the Women’s Institute Library of Cookery 1925)



PRINCIPLES OF CANNING

8. CANNING consists in sealing foods in receptacles, such as cans or jars, in such a way that they will remain sterile for an indefinite period of time. Several methods of canning are in use, and the one to adopt will depend considerably on personal preference and the money that can be expended for the equipment. In any case, successful results in canning depend on the care that is given to every detail that enters into the work. This means, then, that from the selection of the food to be canned to the final operation in canning not one thing that has to do with good results should be overlooked
.
9. SELECTION OF FOOD FOR CANNING.--A careful selection of the food that is to be canned is of great importance. If it is in good condition at the time of canning, it is much more likely to remain good when canned than food that is not. The flavor of the finished product also depends a great deal on the condition of the food. Fruits have the best flavor when they are ripe, but they are in the best condition for canning just before they have completely ripened. Immediately following perfect ripeness comes the spoiling stage, and if fruits, as well as vegetables, are canned before they are completely ripe, they are, of course, farther from the conditions that tend to spoil them. This, however, does not mean that green fruits or vegetables should be canned.

Whenever possible, any food that is to be canned should be perfectly fresh. The sooner it is canned after it has been gathered, the more satisfactory will be the results. For instance, it is better to can it 12 hours after gathering than 24 hours, but to can it 2 hours after is much better. Fruits, such as berries, that are especially perishable should not be allowed to stand overnight if this can be prevented; and it is absolutely necessary to can some vegetables, such as peas, beans, and corn, within a very few hours after gathering. Unless this is done, they will develop a bad flavor because of flat sour, a condition that results from the action of certain bacteria. Imperfect fruits should not be canned, but should be used for making jam, marmalade, or jelly.

10. WHY CANNED FOODS SPOIL.--Canned foods spoil because of the action of micro-organisms that cause fermentation, putrefaction, and molding. The reasons for the spoiling of food are thoroughly discussed in Essentials of Cookery, Part 2, and in that discussion canning is mentioned as one of the means of preserving food or preventing it from spoiling. However, when canning does not prove effective, it is because undesirable bacteria are present in the food. Either they have not been destroyed by the canning process or they have been allowed to enter before the jar was closed, and have then developed to such an extent as to cause the food to spoil. Odors, flavors, and gases result from the putrefaction, fermentation, or molding caused by these bacteria, and these make the foods offensive or harmful, or perhaps both.

11. PREVENTING CANNED FOODS FROM SPOILING.--From what has just been said, it will be seen that the success of canning depends entirely on destroying harmful micro-organisms that are present in the food and preventing those present in the air from entering the jars in which the food is placed.

Some foods are more difficult to keep than others, because bacteria act on them more readily and the foods themselves contain nothing that prevents their growth. Among such foods are meat, fish, peas, corn, beans, and meat soups. On the other hand, some foods contain acids that prevent the growth of bacteria, and these keep easily. Among these are rhubarb, cranberries, and green gooseberries. However, foods that keep easily are few, and in most cases extreme care in the process of canning must be exercised.

12. While warmth is necessary for bacterial growth, very high temperatures will destroy or retard it. In canning, a temperature as high as 212 degrees Fahrenheit, or boiling point, retards the growth of active bacteria, but retarding their growth is not sufficient. They must be rendered inactive. To do this requires either a higher temperature than boiling point or long continued cooking at 212 degrees. Spores are a protective form that many kinds of bacteria assume under unfavorable conditions. They are very difficult to kill, and unless they are completely destroyed in the canning process, they will develop into active bacteria when conditions again become favorable. The result of the spore development is the spoiling of the food.

13. Other things besides the application of heat assist in the keeping of canned food, as, for example, the acids of the fruits and vegetables themselves, as has been mentioned. The use of sugar also assists; the greater the quantity of sugar in solution the easier it will be to keep the food. This is proved in the case of jams and jellies, which will keep without being sealed tight or put into jars immediately after cooking. Salt helps to keep vegetables that are canned, and, in making butters, conserves, and pickles, the spices and vinegars used help to protect the foods from bacterial action. However, none of these things are essential to the keeping of any sterile food, by which is meant food in which all bacteria or sources of bacteria have been rendered inactive by the application of sufficient heat.

14. CANNING PRESERVATIVES.--Numerous compounds, usually in the form of powders, are advertised as being useful for keeping canned foods from spoiling. None of them should be used, however, because they are unnecessary. If the work of canning is carefully and effectively done, good foods will keep perfectly without the addition of a preservative. The pure-food laws of the United States and of many of the states themselves forbid the use of some preservatives because of their harmful effect on the human system. For this reason, to say nothing of the extra expense that would be incurred in their use, such preservatives may well be left alone.