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Home , Canning

FCS3-325 This guide, containing up-to-date instructions for preparing safe Know Your Altitude home-canned , is based on research conducted at the Pennsylvania State It is important to know your University. It is adapted from the USDA approximate elevation or altitude Complete Guide to . above sea level in order to deter- mine a safe processing time for Other publications in the home- canned foods. Since the boiling canning series include: temperature of liquid is lower at • FCS3-121, Canning Tomatoes and higher elevations, it is critical that additional time be given for the safe processing of foods at alti- • FCS3-326, Selecting, Preparing, and tudes above sea level. Canning and Fruit Products • FCS3-327, Selecting, Preparing, and All towns and communities in Canning Tomatoes and Tomato Products Kentucky are below 2,000 feet. The processing times given in this • FCS3-328, Selecting, Preparing, and canning guide are for altitudes up Canning and to 3,000 feet and are safe for all Products parts of our state. • FCS3-329, Preparing and Canning Poultry, Red , and Fish • FCS3-330, Preparing and Canning DANGER! Fermented Foods and Pickled Vegetables • FCS3-331, Preparing and Canning Guard Against Jams and Jellies Poisoning These publications are also available on our web site at: Pressure canning is the only http://www.ca.uky.edu/agc/pubs/pubs.htm recommended method for canning meat, poultry, , and most No product endorsement is implied, nor vegetables. The bacterium is discrimination against similar products in low-acid intended, by the mention of brand names foods is destroyed when they are in this publication. processed at the correct time and pressure in pressure canners. Using boiling-water canners for these foods poses a real risk of poisoning. If these bacteria survive and grow inside a sealed of food, they can produce a poisonous toxin. Even a taste of food contain- ing this toxin can be fatal. Low-acid foods should be boiled after their are opened, even if you detect no signs of spoilage and Revised and adapted for use in Kentucky are certain the food has been by Sue Burrier, former Extension Food properly processed. In Kentucky, and Nutrition Specialist boiling for 13 minutes destroys the toxin that causes poisoning. Contact: Sandra Bastin, Ph.D., R.D., Extension Specialist in Food and Nutrition Contents Introduction to Why Can Foods? ...... 4 the Complete How Canning Preserves Foods ...... 4 Guide to Home Ensuring Safe Canned Foods...... 4 Food acidity & processing methods ... 5 Canning Equipment & methods NOT Home canning has changed greatly in recommended ...... 5 the 170 years since it was introduced as Ensuring High-Quality Canned Foods .... 6 a way to preserve food. Scientists have Maintaining color & flavor in found ways to produce safer, higher canned food ...... 6 quality products. The first part of this series explains the scientific principles Advantages of hot packing ...... 7 on which canning techniques are based, Controlling headspace ...... 7 discusses canning equipment, and de- Jars and ...... 7 scribes the proper use of jars and lids. It Jar cleaning ...... 8 describes basic canning ingredients and procedures and how to use them to achieve Sterilization of empty jars ...... 8 safe, high-quality canned products. selection, preparation & use ...... 8 The remaining publications in this Selecting the Correct Processing Time .. 9 series consist of canning guides for Recommended Canners ...... 9 specific foods. These guides offer detailed Boiling-water canners ...... 9 directions for making syrups and for canning and fruit products, Using boiling-water canners ...... 10 tomatoes and tomato products, veg- Pressure canners ...... 10 etables, red , poultry, , Using pressure canners ...... 11 pickles, and relishes. Handy guidelines Cooling Jars ...... 11 for choosing the correct quantity and quality of raw foods accompany each set Testing Jar Seals ...... 12 of directions for fruits, tomatoes, and Reprocessing Unsealed Jars ...... 12 vegetables. Most recipes are designed to yield a full canner load of pints or quarts. Storing Canned Foods ...... 12 Identifying and Handling Spoiled Canned Food ...... 12 This publication contains many Detoxification process ...... 13 new research-based recommen- Canned Foods for Special Diets ...... 13 dations for canning safer and Canning without sugar ...... 13 better quality food at home. It is Canning without an invaluable resource for persons (reduced sodium) ...... 13 who are canning for the first time. Glossary ...... 14 Experienced canners will find Do Your Canned Foods Pass updated information to help them This Quality Test? ...... 16 improve their canning practices. • activity of food enzymes, Why Can Foods? • reactions with oxygen, and • moisture loss. Canning can be a safe and economical Microorganisms live and multiply way to preserve quality food at home. quickly on the surfaces of Disregarding the value of your labor, and on the inside of bruised, canning homegrown food may save you insect-damaged, and diseased food. half the cost of buying commercially Oxygen and enzymes are present canned food. Canning favorite and throughout fresh food tissues. special products to be enjoyed by family Proper canning practices include: and friends is a fulfilling experience and • carefully selecting and washing fresh a source of pride for many people. food, Many vegetables begin losing some of • peeling some fresh foods, their vitamins when harvested. Nearly half • hot packing many foods, the vitamins may be lost within a few days • adding acids (lemon juice, citric acid, unless the fresh produce is cooled or or vinegar) to some foods, preserved. Within one to two weeks, even • using acceptable jars and self-sealing refrigerated produce loses half or more of lids, and some of its vitamins. The heating process • processing jars in a boiling-water or during canning destroys from one-third to pressure canner for the correct time. one-half of vitamins A and C, thiamin, and Collectively, these practices remove riboflavin. Once canned, additional losses oxygen; destroy enzymes; prevent the of these sensitive vitamins are from growth of undesirable bacteria, yeasts, 5 percent to 20 percent each year. The and molds; and help form a high vacuum amounts of other vitamins, however, are in jars. High vacuums form tight seals only slightly lower in canned compared which keep liquid in and air and micro- with fresh food. If vegetables are handled organisms out. properly and canned promptly after harvest, they can be more nutritious than fresh produce sold in local stores. The advantages of home canning are lost when you start with poor quality Ensuring Safe fresh foods, when jars fail to seal prop- erly, when food spoils, and when flavors, Canned Foods texture, color, and nutrients deteriorate during prolonged storage. Growth of the bacterium Clostridium The information and guides that follow botulinum in canned food may cause explain many of these problems and botulism—a deadly form of food poison- recommend ways to minimize them. ing. These bacteria exist either as spores or as vegetative cells. The spores, which are comparable to plant seeds, can survive harmlessly in soil and water for many years. When ideal conditions exist How Canning for growth, the spores produce vegetative cells which multiply rapidly and may Preserves Foods produce a deadly toxin within three to four days of growth in an environment The high percentage of water in most consisting of: fresh foods makes them very perishable. They spoil or lose their quality for several • a moist, low-acid food, reasons: • a temperature between 40°F and 120°F, and • growth of undesirable microorganisms— • less than 2 percent oxygen. bacteria, molds, and yeasts,

4 Botulinum spores are on most fresh Although tomatoes usually are food surfaces. Because they grow only in considered an acid food, some are now the absence of air, they are harmless on known to have pH values slightly above fresh foods. 4.6. Figs also have pH values slightly Most bacteria, yeasts, and molds are above 4.6. Therefore, if they are to be difficult to remove from food surfaces. canned as acid foods, these products Washing fresh food reduces their num- must be acidified to a pH of 4.6 or bers only slightly. Peeling root crops, lower with lemon juice or citric acid. underground stem crops, and tomatoes Properly acidified tomatoes and figs are reduces their numbers greatly. Blanch- acid foods and can be safely processed ing also helps, but the vital controls are in a boiling-water canner. the method of canning and use of the Botulinum spores are very hard to recommended research-based processing destroy at boiling-water temperatures; times found in the publications of this the higher the canner temperature, the home-canning series. These processing more easily they are destroyed. There- times ensure destruction of the largest fore, all low-acid foods should be steril- expected number of heat-resistant ized at temperatures of 240°F to 250°F, microorganisms in home-canned foods. attainable with pressure canners Properly sterilized canned food will be operated at 10 to 15 PSIG. (PSIG means free of spoilage if lids seal and jars are pounds per square inch of pressure as stored below 95°F. Storing jars at 50°F to measured by a gauge.) At these tem- 70°F enhances retention of quality. peratures, the time needed to destroy bacteria in low-acid canned foods Food acidity & ranges from 20 to 100 minutes. The exact time depends on the kind of methods being canned, the way it is packed into Whether food should be processed in a jars, and the size of jars. The time pressure canner or boiling-water canner to needed to safely process low-acid foods control botulism bacteria depends on the in boiling water ranges from seven to acidity in the food. Acidity may be natural, 11 hours; the time needed to process as in most fruits, or added, as in pickled acid foods in boiling water varies from food. Low-acid canned foods contain too five to 85 minutes. little acidity to prevent the growth of these bacteria. Acid foods contain enough acidity Equipment & methods to block their growth or to destroy them rapidly when heated. The term “pH” is a NOT recommended measure of acidity; the lower its value, the Open-kettle canning and the process- more acidic the food. The acidity level in ing of freshly filled jars in conventional foods can be increased by adding lemon ovens, microwave ovens, and dishwash- juice, citric acid, or vinegar. ers are not recommended because these Low-acid foods have pH values higher practices do not prevent all risks of than 4.6. They include red meats, seafood, spoilage. Steam canners are not recom- poultry, milk, and all fresh vegetables mended because processing times for except for most tomatoes. Most products use with current models have not been that are mixtures of low-acid and acid adequately researched. Because steam foods also have pH values above 4.6 unless canners may not heat foods in the same their ingredients include enough lemon manner as boiling-water canners, their juice, citric acid, or vinegar to make them use with boiling-water processing times acid foods. Acid foods have a pH of 4.6 or may result in spoilage. So-called canning lower. They include fruits, pickles, powders are useless as preservatives and sauerkraut, jams, jellies, marmalade, and do not replace the need for proper heat fruit butters. processing.

5 It is not recommended that pressures Maintaining color & in excess of 15 PSIG be applied when using new pressure-canning equipment. flavor in canned food Jars with wire bails and caps To maintain good natural color and make attractive antiques or storage flavor in stored canned food, you must: for dry food ingredients but are not recommended for canning. • remove oxygen from food tissues and One-piece, porcelain-lined, zinc caps are jars, also no longer recommended. Both glass • quickly destroy the food enzymes, and and zinc caps use flat rubber rings for • obtain high jar vacuums and airtight sealing jars but too often fail to seal jar seals. properly. Follow these guidelines to ensure that your canned foods retain optimal colors and flavors during processing and storage: • Use only high-quality foods that are at Ensuring the proper maturity and are free of dis- eases and bruises. High-Quality • Use the hot-pack method, especially with acid foods to be processed in boil- Canned Foods ing water. • Don’t unnecessarily expose prepared foods Begin with good-quality fresh foods to air; can them as soon as possible. suitable for canning. Quality varies • While preparing a canner load of jars, among varieties of fruits and vegetables. keep peeled, halved, quartered, sliced Many county Extension offices can or diced apples, apricots, nectarines, recommend varieties best suited for , and pears in a solution of 3 canning. grams (3000 milligrams) ascorbic acid Examine food carefully for freshness to 1 gallon of cold water. This proce- and wholesomeness. Discard diseased dure is also useful in maintaining the and moldy food. Trim small diseased natural color of mushrooms and pota- lesions or spots from food. toes and for preventing stem-end dis- Can fruits and vegetables picked from coloration in cherries and grapes. You your garden or purchased from nearby can get ascorbic acid in several forms: producers when the products are at their Pure powdered form—seasonally avail- peak of quality—within six to 12 hours able among canning supplies in super- after harvest for most vegetables. For markets. One level teaspoon of pure best quality, apricots, nectarines, powder weighs about 3 grams. Use peaches, pears, and plums should be 1 teaspoon per gallon of water as a ripened one or more days between treatment solution. harvest and canning. If you must delay tablets—economical and the canning of other fresh produce, keep available year-round in many stores. Buy it in a shady, cool place. 500-milligram tablets; crush and dis- Fresh home-slaughtered red meats solve six tablets per gallon of water as a and poultry should be chilled and treatment solution. canned without delay. Do not can meat Commercially prepared mixes of ascor- from sickly or diseased animals. Put fish bic and citric acid—seasonally available and seafoods on ice after harvest, evis- among canning supplies in supermar- cerate immediately, and can them within kets. Sometimes citric acid powder is two days. sold in supermarkets, but it is less effective in controlling discoloration. If you choose to use these products, follow the manufacturer’s directions.

6 • Fill hot foods into jars and adjust Controlling headspace headspace as specified in recipes. • Tighten screw bands securely, but if The unfilled space above the food in a you are especially strong, not as tightly jar and below its lid is termed as possible. headspace. Directions for canning • Process and cool jars. specify leaving • Store the jars in a relatively cool, dark ¼-inch for jams and jellies, ½-inch for place, preferably between 50°F and 70°F. fruits and tomatoes to be processed in • Can no more food than you will use boiling water, and from 1 to 1¼ inches within a year. in low-acid foods to be processed in a pressure canner. This space is needed for expansion of Advantages food as jars are processed and for form- of hot packing ing vacuums in cooled jars. The extent of expansion is determined by the air Many fresh foods contain from 10 content in the food and by the process- percent to more than 30 percent air. How ing temperature. Air expands greatly long canned food retains high quality when heated to high temperatures; the depends on how much air is removed higher the temperature, the greater the from food before jars are sealed. The expansion. Foods expand less than air more air that is removed, the higher the when heated. quality of the canned product. Raw-packing is the practice of filling jars tightly with freshly prepared but unheated food. Such foods, especially fruit, will float in the jars. The entrapped Jars and Lids air in and around the food may cause discoloration within two to three months Food may be canned in glass jars or of storage. Raw-packing is more suitable metal containers. Metal containers can for vegetables processed in a pressure be used only once. They require special canner. sealing equipment and are much more Hot-packing is the practice of heating costly than jars. freshly prepared food to boiling, simmer- It is recommended that Mason-type jars ing it three to five minutes, and promptly designed for home canning be used for filling jars loosely with the boiled food. preserving food by pressure or boiling- Hot-packing is the best way to remove water canning. Regular and widemouthed air and is the preferred pack style for threaded Mason jars with self-sealing lids foods processed in a boiling-water can- are the best choices. They are available in ner. At first, the color of hot-packed half-pint, pint, 1.5-pint, and quart sizes. foods may appear no better than that of The standard jar mouth opening is about 3 raw-packed foods, but within a short 2 /8 inches. Widemouthed jars have storage period both color and flavor of openings of about 3 inches, making them hot-packed foods will be superior. more easily filled and emptied. Whether food has been hot-packed or Regular-mouth decorator jelly jars are raw-packed, the juice, syrup, or water to available in 8- and 12-ounce sizes. be added to the foods should be heated With careful use and handling, Mason to boiling before it is added to the jars. jars may be reused many times, requir- This practice helps to remove air from ing only new lids each time. When lids food tissues, shrinks food, helps keep are used properly, jar seals and vacuums the food from floating in the jars, in- are excellent. creases vacuum in sealed jars, and improves . Preshrinking food permits adding more food into each jar.

7 Jar cleaning It is best to buy only the quantity of lids you will use in a year. To ensure a Before reuse, wash empty jars in hot good seal, carefully follow the water with detergent and rinse well by manufacturer’s directions in preparing hand, or wash in a dishwasher. Unrinsed lids for use. Examine all metal lids detergents may cause unnatural flavors carefully. Do not use old, dented, or and colors. These washing methods do deformed lids or lids with gaps or other not sterilize jars. Scale or hard-water defects in the sealing gasket. films on jars are easily removed by soak- After filling jars with food, release air ing jars several hours in a solution bubbles by inserting a flat plastic (not containing 1cup of vinegar (5 percent) metal) spatula between the food and the per gallon of water. jar. Slowly turn the jar and move the spatula up and down to allow air bubbles Sterilization to escape. Adjust the headspace and then of empty jars clean the jar rim (sealing surface) with a dampened towel. Place the lid, Use sterile jars for all jams, jellies, and gasket down, onto the cleaned jar-sealing pickled products processed less than 10 surface. Uncleaned jar-sealing surfaces minutes. To sterilize empty jars, put may cause seal failures. them right side up on the rack in a Then fit the metal screw band over the boiling-water canner. Fill the canner and flat lid. Follow the manufacturer’s guide- jars with hot (not boiling) water to 1 inch lines enclosed with or on the for above the tops of the jars. Boil 10 min- tightening the jar lids properly. utes. Remove and drain hot sterilized jars one at a time. Save the hot water for • If screw bands are too tight, air cannot processing filled jars. Fill jars with food, vent during processing, and food will add lids, and tighten screw bands. discolor during storage. Overtightening Empty jars used for vegetables, meats, also may cause lids to buckle and jars and fruits to be processed in a pressure to break, especially with raw-packed, canner need not be sterilized beforehand. pressure-processed food. It is also unnecessary to sterilize jars for • If screw bands are too loose, liquid may fruits, tomatoes, and pickled or fermented escape from jars during processing, foods that will be processed 10 minutes or seals may fail, and the food will need to longer in a boiling-water canner. be reprocessed. Do not retighten lids after processing Lid selection, jars. As jars cool, the contents in the jar contract, pulling the self-sealing lid preparation & use firmly against the jar to form a high The common self-sealing lid consists vacuum. of a flat metal lid held in place by a Screw bands are not needed on stored metal screw band during processing. The jars. They can be removed easily after flat lid is crimped around its bottom edge jars are cooled. When removed, washed, to form a trough, which is filled with a dried, and stored in a dry area, screw colored gasket material. When jars are bands may be used many times. If left on processed, the lid gasket softens and stored jars, they become difficult to flows slightly to cover the jar-sealing remove, often rust, and may not work surface, yet allows air to escape from the properly again. jar. The gasket then forms an airtight seal as the jar cools. Gaskets in unused lids work well for at least five years from date of manufacture. The gasket material in older unused lids may fail to seal on jars.

8 quart-jars or eight to nine pint-jars. Selecting the Small pressure canners hold four quart-jars; some large pressure can- Correct Processing ners hold 18 pint-jars in two layers but hold only seven quart-jars. Pressure Time saucepans with smaller volume capaci- ties are not recommended for use in When food is canned in boiling water, canning. Treat small pressure canners more processing time is needed for most as standard larger canners. They raw-packed foods and for quart jars than should be vented using the typical is needed for hot-packed foods and pint venting procedures. jars. Low-acid foods must be processed in a To destroy microorganisms in acid pressure canner to be free of botulism foods processed in a boiling-water risks. Although pressure canners also canner, you must: may be used for processing acid foods, boiling-water canners are recommended • process jars for the correct number of because they are faster. A pressure can- minutes in boiling water. ner would require from 55 to 100 min- • cool the jars at room temperature. utes to can a load of jars; the total time To destroy microorganisms in low-acid for canning most acid foods in boiling foods processed with a pressure canner, water varies from 25 to 60 minutes. you must: A boiling-water canner loaded with • process the jars for the correct number filled jars requires about 20 to 30 min- of minutes at 240°F (10 PSIG) or 250°F utes of heating before its water begins to (15 PSIG). boil. A loaded pressure canner requires • allow canner to cool at room tempera- about 12 to 15 minutes of heating before ture until it is completely depressurized. it begins to vent, another 10 minutes to The food may spoil if you fail to use vent the canner, another 5 minutes to the proper processing times, fail to vent pressurize the canner, another 8 to 10 steam from canners properly, process at minutes to process the acid food, and, lower pressure than specified, process finally, another 20 to 60 minutes to cool for fewer minutes than specified, or cool the canner before removing jars. the canner with water. Processing times for haft-pint and pint Boiling-water canners jars are the same, as are times for 1.5-pint and quart jars. For some products, you These canners are made of aluminum have a choice of processing at 5, 10, or 15 or porcelain-covered . They have PSIG. In these cases, choose the canner removable perforated racks and fitted pressure (PSIG) you wish to use and match lids. The canner must be deep enough so it with your pack style (raw or hot) and jar that at least 1 inch of briskly boiling size to find the correct processing time. water will cover the tops of jars during processing. Some boiling-water canners do not have flat bottoms. A flat bottom must be used on an electric range. Either a flat or ridged bottom can be Recommended used on a gas burner. To ensure uniform processing of all jars with an electric Canners range, the canner should be no more than 4 inches wider in diameter than the There are two main types of canners element on which it is heated. for heat-processing home-canned food: boiling-water canners and pressure canners. Most are designed to hold seven

9 Using certain period of time do. The success of destroying all microorganisms capable of boiling-water canners growing in canned food is based on the temperature obtained in pure steam, free Follow these steps for successful of air, at sea level. At sea level, a canner boiling-water canning: operated at a gauge pressure of 10 pounds 1. Fill the canner halfway with water. provides an internal temperature of 240°F. 2. Preheat water to 140°F for Air trapped in a canner lowers the raw-packed foods and to 180°F for inside temperature and results in hot-packed foods. underprocessing. The highest volume of 3. Load filled jars, fitted with lids, into air trapped in a canner occurs in process- the canner rack and use the handles ing raw-packed foods in dial-gauge can- to lower the rack into the water; or ners. These canners do not vent air during fill the canner, one jar at a time, with processing. To be safe, all types of pres- a jar lifter. sure canners must be vented 10 minutes 4. Add more boiling water, if needed, so before they are pressurized. the water level is at least 1 inch above To vent a canner, leave the vent port jar tops. uncovered on newer models or manually 5. Turn heat to its highest position until open petcocks on some older models. water boils vigorously. Heating the filled canner with its lid locked 6. Set a timer for the minutes required into place boils water and generates steam for processing the food. that escapes through the petcock or vent 7. Cover with the canner lid and lower port. When steam first escapes, set a timer the heat setting to maintain a gentle for 10 minutes. After venting 10 minutes, boil throughout the processing time. close the petcock or place the counter- 8. Add more boiling water, if needed, to weight or weighted gauge over the vent keep the water level above the jars. port to pressurize the canner. 9. When jars have been boiled for the Weighted-gauge models exhaust tiny recommended time, turn off the heat amounts of air and steam each time their and remove the canner lid. gauge rocks or jiggles during processing. 10. Using a jar lifter, remove the jars and The sound of the weight rocking or jiggling place them on a towel, leaving at indicates that the canner is maintaining least 1 inch of space between the jars the recommended pressure and needs no during cooling. further attention until the load has been processed for the set time. Weighted-gauge Pressure canners canners cannot correct precisely for higher Pressure canners for use in the home altitudes, and at altitudes above 1,000 feet have been extensively redesigned in recent must be operated at a pressure of 15. years. Models made before the 1970s were Check dial gauges for accuracy before heavy-walled kettles with clamp-on or use each year and replace if they read turn-on lids. They were fitted with a dial high by more than 1 pound at 5, 10, or gauge, a vent port in the form of a petcock 15 pounds of pressure. Low readings or counterweight, and a safety fuse. cause overprocessing and may indicate Modern pressure canners are lightweight, that the accuracy of the gauge is unpre- thin-walled kettles; most have turn-on dictable. If a gauge is consistently low, lids. They have a jar rack, gasket, dial or you may adjust the processing pressure. weighted gauge, an automatic vent or For example, if the directions call for 12 cover lock, a vent port (steam vent) that is pounds of pressure and your dial gauge closed with a counterweight or weighted has tested 1 pound low, you can safely gauge, and a safety fuse. process at 11 pounds of pressure. If the Pressure does not destroy microorgan- gauge is more than 2 pounds low, it is isms, but high temperatures applied for a unpredictable, and it is best to replace it.

10 Gauges may be checked at most county tions during processing may cause Extension offices. unnecessary liquid losses from jars. Handle gaskets of canner lids carefully Weighted gauges on Mirro canners and clean them according to the should jiggle about two or three manufacturer’s directions. Nicked or times per minute. On Presto canners, dried gaskets will allow steam leaks they should rock slowly throughout during pressurization of canners. Gas- the process. kets of older canners may need to be 6. When processing time is completed, lightly coated with once per turn off the heat, remove the canner year, but newer models are from heat if possible, and let the can- pre-lubricated. Check your canner’s ner depressurize. Do not force-cool the instructions. canner. If you cool it with cold run- Lid safety fuses are thin metal inserts ning water in a sink or open the vent or rubber plugs designed to relieve port before the canner depressurizes excessive pressure from the canner. Do by itself, liquid will spurt from jars, not pick at or scratch fuses while clean- causing low liquid levels and jar seal ing lids. Use only canners that have failures. Force-cooling also may warp Underwriter’s Laboratory (UL) approval the canner lid of older model can- to ensure their safety. ners, causing steam leaks. Replacement gauges and other parts Depressurization of older models for canners are often available at stores should be timed. Standard size offering canner equipment or from heavy-walled canners require about canner manufacturers. Order parts, list 30 minutes when loaded with pints canner model number, and describe the and 45 minutes with quarts. Newer parts needed. thin-walled canners cool more rapidly and are equipped with vent locks. Using pressure canners These canners are depressurized Follow these steps for successful when their vent lock piston drops to pressure canning: a normal position. 7. After the vent port or petcock has 1. Put 2 to 3 inches of hot water in the been open for two minutes, unfasten canner. Place filled jars on the rack, the lid and carefully remove it. Lift using a jar lifter. Fasten canner lid the lid away from you so that the securely. steam does not burn your face. 2. Open petcock or leave weight off vent 8. Remove jars with a lifter, and place port. Heat at the highest setting until on towel or cooling rack, if desired. steam flows from the petcock or vent port. 3. Maintain high heat setting, exhaust steam 10 minutes, and then place weight on vent port or close petcock. Cooling Jars The canner will pressurize during the Cool the jars at room temperature for next three to five minutes. 12 to 24 hours. Jars may be cooled on 4. Start timing the process when the racks or towels to minimize heat damage pressure reading on the dial gauge in- to counters. The food level and liquid dicates that the recommended pressure volume of raw-packed jars will be notice- has been reached or when the weighted ably lower after cooling because air is gauge begins to jiggle or rock. exhausted during processing and food 5. Regulate heat under the canner to shrinks. If a jar loses excessive liquid maintain a steady pressure at or during processing, do not open it to add slightly above the correct gauge pres- more liquid. As long as the seal is good, sure. Quick and large pressure varia- the product is still usable.

11 Testing Jar Seals Storing Canned After cooling jars for 12 to 24 hours, Foods remove the screw bands and test seals with one of the following methods: If lids are tightly vacuum-sealed on Method 1: Press the middle of the lid cooled jars, remove screw bands, wash with a finger or thumb. If the lid springs the lid and jar to remove food residue, up when you release your finger, the lid then rinse and dry jars. and date is unsealed and reprocessing will be the jars and store them in a clean, cool, necessary. dark, dry place. Do not store jars at Method 2: Tap the lid with the bottom temperatures above 95°F or near hot of a teaspoon. If it makes a dull sound, pipes, a range, a furnace, in an the lid is not sealed. If food is in contact uninsulated attic, or in direct sunlight. with the underside of the lid, it will also Under these conditions, food will lose cause a dull sound. If the jar lid is sealed quality in a few weeks or months and correctly, it will make a ringing, high- may spoil. Dampness may corrode metal pitched sound. lids, break seals, and allow recontamina- Method 3: Hold the jar at eye level tion and spoilage. and look across the lid. The lid should be Accidental freezing of canned foods concave (curved down slightly in the will not cause spoilage unless jars be- center). If center of the lid is either flat or come unsealed and recontaminated. bulging, it may not be sealed. However, freezing and thawing may soften food. If jars must be stored where they may freeze, wrap them in newspa- pers, place them in heavy , and cover them with more newspapers and Reprocessing blankets. Unsealed Jars If a jar fails to seal, remove the lid and check the jar-sealing surface for tiny Identifying and nicks. If necessary, change the jar, add a new, properly prepared lid, and repro- Handling Spoiled cess within 24 hours using the same processing time. Canned Food Another option is to adjust headspace in unsealed jars to 1½ inches and freeze Growth of spoilage bacteria and yeast jars and contents instead of reprocess- produces gas which pressurizes the food, ing. However, make sure jars have swells lids, and breaks jar seals. As each straight sides. Freezing may crack jars stored jar is selected for use, examine its with “shoulders.” lid for tightness and vacuum. Lids with Foods in single unsealed jars could be concave centers have good seals. stored in the refrigerator and consumed Next, while holding the jar upright at within several days. eye level, rotate the jar and examine its outside surface for streaks of dried food originating at the top of the jar. Look at the contents for rising air bubbles and unnatural color. While opening the jar, smell for un- natural odors and look for spurting

12 liquid and cottonlike mold growth (white, blue, black, or green) on the top food Canned Foods for surface and underside of lid. Do not taste food from a stored jar you discover Special Diets to have an unsealed lid or that otherwise shows signs of spoilage. The cost of commercially canned All suspect containers of spoiled special often prompts interest low-acid foods should be treated as in preparing these products at home. having produced botulinum toxin and Some low-sugar and low-salt foods may should be handled carefully as follows: be easily and safely canned at home. However, the color, flavor, and texture of • If the suspect glass jars are unsealed, these foods may be different than ex- open, or leaking, they should be detoxi- pected and be less acceptable. fied before disposal. • If the suspect glass jars are sealed, re- Canning without sugar move lids and detoxify the entire jar, contents, and lids. In canning regular fruits without sugar, it is very important to select fully Detoxification process ripe but firm fruits of the best quality. Prepare these as described for hot packs Carefully place the suspect containers in FCS3-326, Selecting, Preparing, and and lids on their sides in an 8-quart Canning Fruit and Fruit Products. Juice volume or larger stockpot, pan, or made from the fruit being canned is best. boiling-water canner. Wash your hands Blends of unsweetened apple, , thoroughly. Carefully add water to the and white grape juice are also good for pot. The water should completely cover pouring over solid fruit pieces. Adjust the containers with a minimum of a headspaces and lids and use the pro- 1 inch of water above the containers. cessing recommendations for regular Avoid splashing the water. Place a lid on fruits. Add sugar substitutes, if desired, the pot and heat the water to boiling. when serving. Also see FCS3-331, Pre- Boil 30 minutes to ensure detoxifying the paring and Canning Jams and Jellies. food and all components. Cool and discard lids and food in the trash or Canning without salt bury in the soil. Thoroughly clean all counters, con- (reduced sodium) tainers, and equipment, including can To can tomatoes, vegetables, meats, opener, clothing, and hands that may poultry and seafoods, use the procedures have come in contact with the food or the given in other publications in the home- containers. Discard any sponges or canning series, but omit the salt. Con- washcloths that were used in the sult your county Extension office for cleanup. Place them in a plastic and these publications: FCS3-327, Selecting, discard in the trash. Preparing, and Canning Tomatoes and Tomato Products; FCS3-328, Selecting, Preparing, and Canning Vegetables and Vegetable Products; and FCS3-329, Preparing and Canning Poultry, Red Meat, and Fish. In these products, salt seasons the food but is not necessary to ensure its safety. Add salt substitutes, if de- sired, when serving.

13 incorrectly to refer to foods that are Glossary open-kettle canned or jars that are heat-processed in boiling water. Acid Foods—Foods that contain Enzymes—Proteins in food which enough acid to result in a pH of 4.6 or accelerate many flavor, color, texture, lower. Includes most tomatoes; fer- and nutritional changes, especially when mented and pickled vegetables; relishes; food is cut, sliced, crushed, bruised, and jams, jellies, and marmalades; and all exposed to air. Proper blanching or fruits except figs. Acid foods may be hot-packing practices destroy enzymes processed in boiling water. and improve . Ascorbic Acid—The chemical name Exhausting—Removal of air from for vitamin C; commonly used to prevent within and around food and from jars browning of peeled, light-colored fruits and canners. Exhausting or venting of and vegetables. pressure canners is necessary to prevent Blancher—A 6- to 8-quart lidded pot botulism in low-acid canned foods. designed with a fitted, perforated basket Headspace—The unfilled space above to hold food in boiling water or with a food or liquid in jars that allows for food fitted rack to steam foods. Useful for expansion as jars are heated and for loosening skins on fruits to be peeled or forming vacuums as jars cool. for heating foods to be hot packed. Heat Processing—Treatment of jars Boiling-Water Canner—A large, with sufficient heat to enable storing standard-sized, lidded kettle with jar rack food at normal home temperatures. designed for heat-processing 7 quarts or 8 —An absolutely airtight to 9 pints in boiling water. container seal which prevents reentry of Botulism—An illness caused by eating air or microorganisms into packaged toxin produced by growth of Clostridium foods. botulinum bacteria in moist, low-acid food Hot Pack—Heating of raw food in containing less than 2 percent oxygen and boiling water or steam and filling it hot stored between 40°F and 120°F. Proper into jars. heat processing destroys this bacterium in canned food. Freezer temperatures inhibit Low-Acid Foods—Foods that contain its growth in . Low moisture very little acid and have a pH above 4.6. controls its growth in dried food. High The acidity in these foods is insufficient oxygen controls its growth in fresh foods. to prevent the growth of botulism bacte- ria. Vegetables, some varieties of toma- Canning—A method of preserving food toes, figs, all meats, fish, seafoods, and which employs heat processing in air- some products are low-acid foods. tight, vacuum-sealed containers so that To control all risks of botulism, jars of food can be safely stored at normal home these foods must be (1) heat processed in temperatures. a pressure canner or (2) acidified to a pH Canning Salt—Also called of 4.6 or lower before processing in salt. It is regular table salt without the boiling water. anti-caking or iodine additives. Microorganisms—Independent organ- Citric Acid—A form of acid that can isms of microscopic size, including be added to canned foods. It increases bacteria, yeast, and mold. In a suitable the acidity of low-acid foods and may environment, they grow rapidly and may improve their flavor. divide or reproduce every 10 to 30 min- Cold Pack—Canning procedure in utes. Therefore, they reach high popula- which jars are filled with raw food. “Raw tions very quickly. Microorganisms are pack” is the preferred term for describing sometimes intentionally added to fer- this practice. “Cold pack” is often used ment foods, make antibiotics, and for

14 other reasons. Undesirable microorgan- Pressure Canner—A specifically isms cause disease and food spoilage. designed metal kettle with a lockable lid Mold—A fungus-type microorganism used for heat processing low-acid food. whose growth on food is usually visible These canners have jar racks, one or and colorful. Molds may grow on many more safety devices, systems for ex- foods, including acid foods like jams and hausting air, and a way to measure or jellies and canned fruits. Recommended control pressure. Canners with 20- to heat processing and sealing practices 21-quart capacity are common. The prevent their growth on these foods. minimum size of canner that should be used has a 16-quart capacity and can Mycotoxins—Toxins produced by the hold 7 quart-jars. Use of pressure sauce- growth of some molds on foods. pans with a capacity of less than 16 Open-Kettle Canning—A quarts is not recommended. nonrecommended canning method. Food Raw Pack—The practice of filling jars is heat-processed in a covered kettle, filled with raw, unheated food. Acceptable for while hot into sterile jars, and then sealed. canning low-acid foods but allows more Foods canned this way have low vacuums rapid quality losses in acid foods that are or too much air, which permits rapid loss heat-processed in boiling water. Also of quality in foods. Also, these foods often called “cold pack.” spoil because they become recontaminated while the jars are being filled. Style of Pack—Form of canned food, such as whole, sliced, piece, juice, or —Heating food to sauce. The term may also be used to temperatures high enough to destroy reveal whether food is filled raw or hot disease-causing microorganisms. into jars. pH—A measure of acidity or alkalinity. Vacuum—A state of negative pressure Values range from 0 to 14. A food is that reflects how thoroughly air is re- neutral when its pH is 7.0: lower values moved from within a jar of processed are increasingly more acidic; higher food; the higher the vacuum, the less air values are increasingly more alkaline. left in the jar. PSIG—Pounds per square inch of pressure as measured by a gauge.

15 Do Your Canned Foods Pass This Quality Test? OVERALL APPEARANCE ❑ Good proportion of solid to liquid ❑ Full pack with proper headspace ❑ Liquid just covering solid ❑ Free of air bubbles ❑ Free of imperfections—stems, cores, seeds ❑ Good seals ❑ Practical pack that is done quickly and easily FRUITS & VEGETABLES ❑ Pieces uniform in size and shape ❑ Characteristic, uniform color ❑ Shape retained—not broken or mushy ❑ Proper maturity LIQUID OR SYRUP ❑ Clear and free from sediment

Educational programs of the Kentucky Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, disability, or national origin. Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, C. Oran Little, Director of Cooperative Extension Service, University of Kentucky College of Agriculture, Lexington, and Kentucky State University, Frankfort. Copyright © 2000 for materials developed by the University of Kentucky Cooperative Extension Service. This publication may be reproduced in portions or its entirety for educational or nonprofit purposes only. Permitted users shall give credit to the author(s) and include this copyright notice. Publications are also available on the World Wide Web at: http://www.ca.uky.edu. Issued 3-1988, Last printed 6-2000, 2000 copies,105500 copies to date.