Canning is an of import, prophylactic method of nutrient preservation if adept properly. The canning process involves placing foods in jars and heating them to a temperature that destroys microorganisms that could be a health hazard or cause the food to spoil. Canning also inactivates enzymes that could cause the food to spoil. Air is driven from the jar during heating, and equally information technology cools, a vacuum seal is formed. The vacuum seal prevents air from getting back into the production bringing with information technology microorganisms to recontaminate the food.

Home Canning is an important, safe method of food preservation if practiced properly.

Home Canning is an important, safe method of food preservation if adept properly.
Marie Hegler, ©2016, Clemson Extension

To safely home can foods and prevent food-borne disease, research-based canning methods must be followed. Botulism is the most usually associated food-borne illness with dwelling canned foods. The Centers for Disease Command and Prevention reported that there were 210 outbreaks of botulism from 1996 to 2014, of which 145 were linked to home-canned foods. Food-borne illnesses related to the consumption of dwelling house canned foods are often linked to the person canning the foods not following inquiry-based canning instructions, not using pressure level canners for low-acid foods, and ignoring signs of spoilage or lack of knowledge about botulism in dwelling house canned foods.

Clostridium botulinum leaner are the main reason why pressure canning is absolutely necessary for canning low-acid nutrient. The bacterial cells are killed at humid temperatures, but they can course spores that survive these temperatures. The spores grow well in low-acid foods, in the absenteeism of air, such every bit in canned vegetables and meats. When the spores begin to abound, they produce the deadly botulinum toxin.

These spores can be destroyed past canning the food at a temperature of 240 °F, or above, for the right length of time. This temperature is above the humid point of water (212 °F) so it can simply exist reached in a pressure canner.

Safety Canning Methods

There are three safe means of canning, depending on the type of food beingness canned. These are the boiling water bath method, the atmospheric steam canner method, and the pressure canner method.

Humid H2o Bath Method: The boiling water bath method is safe for fruits, tomatoes and pickles too as jams, jellies and other preserves. In this method, jars of food are heated past being completely covered with boiling h2o (212 °F at bounding main level).

Loftier-acid foods (pH of 4.half-dozen or less) incorporate enough acrid that the Clostridium botulinum spores tin can't abound and produce their mortiferous toxin. High-acid foods include fruits and properly pickled vegetables. These foods can exist safely canned at boiling temperatures in a boiling h2o bath. Tomatoes and figs take pH values close to four.6. To can these in a boiling h2o bath, acid in the form of lemon juice or citric acid must be added.

Atmospheric Steam Canning Method: The steam canner must exist used with naturally acidic or properly acidified foods that have a pH less than or equal to 4.six. This includes well-nigh fruits, preserves, and pickled vegetables. The steam canner is NOT for low-acid foods such as vegetables and meats.

In the past there was non enough research about atmospheric steam canners (i.due east. steam canners) to recommend them to produce prophylactic abode canned foods. All the same, in 2015, Dr. Barbara Ingham with the University of Wisconsin in collaboration with the National Eye for Domicile Food Preservation published a peer-reviewed research study on the use of steam canners. The results of the report provided critical information, and practices that must be followed for the production of prophylactic foods canned in a steam canner in place of a boiling h2o bathroom canner. In steam canners, the prepared jars are set in a rack in a higher place a reservoir of water. The steam created from humid the water provides the thermal treatment to the jars. In that location are several advantages to using a steam canner. A steam canner uses less h2o than a boiling water bath canner, reaches processing temperatures quicker, and requires less free energy.

Pressure Canning Methods: Pressure level canning is the just condom method of canning low-acrid foods (those with a pH of more four.half dozen). These include all vegetables, meats, poultry and seafood. Considering of the danger of botulism, these foods must be canned in a pressure canner. Jars of food are placed in 2 to 3 inches of water in a pressure canner and then heated to a temperature of at least 240 °F. This temperature can but exist reached in a pressure canner.

Choosing a Recipe

Recipes must be developed for the canning method you are using and should only come from enquiry-based sources such as the USDA, the National Heart for Home Food Preservation, and Extension resources. Recipe instructions must include the ingredients, preparation of ingredients, and processing times for acidic and properly acidified foods.

If you are canning at an altitude over 1,000 anxiety, and then check for whatever adjustments for each blazon of food. Canning recipes are usually designed for altitudes of 0-1,000 feet. If y'all are at a higher altitude, then the processing time will demand to be adjusted. While this does not apply to near of Due south Carolina, there are areas in the upstate such as northern Oconee and Pickens county about the Sassafras Mount that are between i,001-3,000 anxiety. Ask your county extension agent to aid yous decide your distance or check with your local airport.

Getting Set to Can

Gather and wash equipment and containers before gathering fruits and vegetables. Assemble products early when they are at their peak of quality. Do not utilize overripe products. Assemble or purchase only as much as yous tin handle within two or 3 hours.

Wash the product carefully, handling small-scale amounts at a time. Elevator the food out of the water, drain the water and go along rinsing until the water is articulate and free of dirt. Dirt contains some of the bacteria that are hardest to impale. Don't let the food soak; it will lose flavour and nutrients. The cleaner the raw foods, the more constructive the canning process. Do not can rust-covered or damaged food items.

Preparing the Jars & Lids: Examine jars and discard those with nicks, cracks and rough edges. These defects will non let an airtight seal on the jar, and food spoilage will result. All canning jars should be washed in soapy water, rinsed well and then kept hot. This could be washed in the dishwasher or by placing the jars in the water that is heating in your canner. The jars need to be kept hot to prevent breakage when they're filled with a hot production and placed in the canner for processing.

Jars that will be filled with nutrient and processed for less than ten minutes in a humid h2o bathroom canner need to be sterilized by boiling them for 10 minutes. NOTE: If you are at an distance of ane,000 feet or more than, boil an boosted minute for each one,000 feet of additional altitude. Jars processed in a boiling water bath canner for 10 minutes or more or in a force per unit area canner will be sterilized during processing.

Be sure to utilise new two-piece lids. Follow the manufacturer'due south instructions for treating them. Some need to exist brought almost to a boil and and so left in hot water, while others demand to be boiled for a menstruation of time.

Methods of Pack

Fruits and vegetables may exist packed raw or they may exist preheated then packed into canning jars. The hot pack yields better color and season, specially when foods are candy in a boiling h2o bath. For both raw pack and hot pack, in that location should be enough syrup, water or juice to fill in around the solid food in the jar and to cover the food. If not covered by liquid, food at the top tends to darken and develop unnatural flavors. Information technology takes from ½ to 1½ cups of liquid for a quart jar.

Raw Pack: For this method put raw, unheated food directly in jars. Pour humid hot water, juice or syrup over the food to obtain proper headspace.

Fruits and most vegetables packed raw should be packed tightly considering they will shrink during processing; even so, corn, lima beans, potatoes and peas should be packed loosely because they aggrandize during canning.

Hot Pack: For this method, heat the food to boiling (or melt it for specified time) and and then pack the hot food and boiling hot liquid in jars. Shrinkage has already taken place, so pack foods loosely enough to allow food to be surrounded by liquid.

Steps for Boiling Water Bath Method

Use the humid h2o bathroom method simply to preserve loftier-acid foods such as fruits, tomatoes and pickles.

  • Fill up the canner about halfway with hot water. Plough on the burner and heat the water.
  • For raw-packed jars, have the water in the canner hot, but not boiling, to preclude breakage of the jars when they're placed in the canner. For hot-packed jars, use hot or gently humid h2o.
  • Make full a single jar at a time, as described above in "Methods of Pack", allow proper headspace, remove air bubbling, and adjust lids as described below, then place the filled jar in the canner.
  • Allow the proper headspace, according to processing directions for specific foods, in order to remove all the actress air during processing, and to grade a tight vacuum seal.
  • Run a bubble freer or any plastic or prophylactic-like utensil around the edges of the jar, gently shifting the food, then that whatsoever trapped air is released. Add more than liquid equally needed to to the jar to ensure proper headspace.
  • Wipe off the rims of the jars with a clean, damp material.
  • Screw on the lids, but not too tightly—air needs to escape during processing.
  • Put filled glass jars on the rack in the canner. Add more boiling water or take out some every bit needed so that the water is at to the lowest degree one inch over the tops of the jars. If you lot add more water, cascade it between the jars, non directly on them, to prevent breakage. Put the lid on the canner and set the heat to its highest setting.
  • When the water in the canner reaches a rolling boil, begin counting the correct processing time. Arrange the heat to maintain a gentle and steady boil, and add more than boiling water as necessary.
  • If the water stops boiling at any time during the process, turn the oestrus on its highest setting, bring the water dorsum to a vigorous boil, and begin the timing of the process over, from the beginning (using the full original processing fourth dimension).
  • When the jars have been processed in boiling h2o for the recommended fourth dimension, turn off the heat and remove the canner lid. Expect 5 minutes before removing jars.
  • Use a jar lifter to advisedly remove the jars. Place the hot jars right side up on a block cooling rack or dry towels to prevent the jars from breaking on contact with a cold surface.
  • Avert placing the jars in a cold typhoon. Exercise not cover with or wrap jars in towels. Leave at least 1 inch of space between jars.
  • Let the jars to cool untouched for 12 to 24 hours. Do not tighten the ring bands on the lids and do not push downward on the heart of the flat metal lids until the jars are completely cooled.

Steps for Atmospheric Steam Canning Method

Use the boiling h2o bathroom method simply to preserve loftier-acid foods such as fruits, tomatoes and pickles. Follow research-based recipes. The recipes provided past the manufacturer of the steam canner are not considered to exist research-tested, and therefore should not exist used. Steam canners may be used with approved recipes using ½ pint, pint or quart jars. The total processing time, including whatsoever adjustments for altitude, must be less than 45 minutes. The processing time is restricted considering there must be enough water to emit pure steam for the full processing time and the canner cannot be opened during processing to add more water.

Atmospheric steam canning is an effective and safe method of food preservation when washed properly past following research-based instructions.
Kimberly Bakery, ©2019, Clemson Extension

  • The steam canner must have the air vented out with pure steam before the processing fourth dimension can begin. Use caution when working almost steam as the hot steam and water can cause serious burns. The pure steam must remain at the temperature of boiling water (212°F at body of water level) at the offset of processing time and throughout the full processing time. The temperature of the steam can be monitored with a thermometer carefully placed in the vent hole. Ensure that the thermometer probe does not touch a jar, which tin cause an inaccurate temperature reading. Note: Do not boil the water too vigorously. This tin can cause the canner to boil dry out in as brusque as twenty minutes, which may be before the processing time is consummate.
  • Preheat the jars earlier filling and fill with hot liquid for raw or hot-pack foods. Minimize cooling earlier the processing begins.
  • The steam canner does not require pre-heating. Nevertheless, pre-heating can assist go on the jars hot afterward filling.
  • Let the jars to exist canned for the full processing fourth dimension.
  • After completing the processing fourth dimension, turn off the estrus and carefully remove the lid abroad from you so that the steam does not burn you. Expect 5 minutes before removing the jars with a jar lifter.
  • Cool the jars on a rack or towel at room temperature and away from any drafts. Keep the jars at to the lowest degree 1-inch apart from each other. Permit the jars to cool at room temperature for 12-24 hours. Note: Practice not forcefulness cool jars. The slow cooling process lends to the greatest destruction of any pathogens that may be nowadays in the jar.

Steps for Pressure Canner Method

Think that pressure canning is the only safe method of processing low–acid foods such as vegetables, meat, poultry and fish. Exist sure to read your manufacturer'southward instructions on the utilise of your force per unit area canner. Dial-gauge canners must be tested for accuracy every year before the canning flavor. Call your local Extension service office to schedule an appointment to have your punch-gauge canner tested.

  • Identify ii to three inches of water in the canner. Information technology should exist hot, simply non humid, when canning raw-packed nutrient; hot or gently humid for hot-packed foods. Make certain you still have 2 to three inches of water when y'all are prepare to load the canner.
  • Fill the jars as described above in "Methods of Pack". Let proper headspace, remove air bubbles, wipe jar rims and put on lids. See detailed instructions above in "Steps for Humid Water Bath Methods".
  • Gear up the jars of food on the rack in the canner so steam can flow around each jar. Fasten the canner lid so that no steam begins to escape except through the vent. Plow estrus to loftier and watch until steam begins to escape from the vent. Let the steam escape steadily for 10 minutes. This step is necessary for all force per unit area canners to remove air that could otherwise lower the temperature and outcome in nether processing.
  • Close the vent using a weight, valve or screw, depending on the type of canner. If you have a weighted-judge canner that has a weight of varying pressures, exist sure you are using the correct pressure.
  • For a dial-gauge canner, let the pressure level rise speedily to 8 pounds of pressure. Conform the burner temperature down slightly and permit the pressure continue to rising to the correct force per unit area. (If the burner were left on high, the pressure would be hard to regulate when the right pressure is reached.) Start counting the processing time as soon as the force per unit area is reached.
  • For weighted-judge canners, let the canner estrus quickly at first then adjust the heat downward slightly until the weight begins to rock gently or "jiggle" two to three times per infinitesimal, depending on the type of canner you have. Start counting the processing time every bit shortly as the weight does either of these.
  • Adjust the heat nether the canner to maintain a steady force per unit area at, or slightly higher up, the correct approximate pressure level. If the force per unit area goes as well high, turn down the estrus under the canner. Do not lower the pressure by opening the vent or lifting the weight.
  • Loss of force per unit area at whatever fourth dimension tin can effect in nether processing or unsafe food. If at any time the pressure goes beneath the recommended amount, bring the canner dorsum to pressure and begin the timing of the procedure over, from the first (using the full original processing time).
  • When the processing is completed, carefully remove the canner from the rut. If the canner is likewise heavy, simply plough it off.
  • Permit the pressure in the canner drib to null. This volition take 30 to 45 minutes in a standard heavy-walled canner and nearly an hour for a larger 22-quart canner. Newer sparse-walled canners depressurize more than quickly. Do not blitz the cooling by setting the canner in water or by running cold water over the canner. Never lift the weight or open the vent to hasten the reduction in force per unit area. Forced cooling may outcome in food spoilage.
  • Older canners are depressurized when the gauge on a dial-gauge canner registers zero or when a gentle nudge to the weight on a weighted estimate canner does non produce steam or resistance. New canners are equipped with a prophylactic lock. These canners are depressurized when the prophylactic lock drops to normal position. When the canner is depressurized, open the vent or remove the weight. Await ten minutes and and so open the canner.
  • Sometimes condom locks that are located in the handle of a canner will stick. If a nudge to a canner weight shows that it is depressurized, remove the weight, wait 10 minutes and then run a knife blade betwixt the handles to release the lock.
  • Unfasten the lid, and tilt the far side up, so the steam escapes abroad from you. Do not leave the jars in the closed canner to absurd, or the food within could begin to spoil.
  • Use a jar lifter to carefully remove the jars from the canner. Place the hot jars on a cake cooling rack or dry towels, right side up to prevent the jars from breaking on contact with a cold surface. Exit at least i inch of infinite between the jars.
  • Do not tighten the lids. Let the jars to cool, untouched for 12 to 24 hours.

Safe Handling of Processed Jars

Test the Lid for a Proper Seal: Nearly two-piece lids will seal with a "popular" audio while they're cooling. When completely cool, test the lid. It should be curved downward and should not movement when pressed with a finger. If a jar is non sealed, refrigerate it and use the unspoiled food inside 2 to 3 days, reprocess within 24 hours, or freeze.

If liquid has been lost from sealed jars do not open them to supplant information technology, simply plan to apply these kickoff. The food may discolor, but if sealed, and the liquid is only a niggling lower than the food, the food is safe.

Label & Store Jars: Remove spiral bands from the sealed jars to forbid them from rusting on. Wash, dry and store screw bands for later use. Wash nutrient residue from the outside of the jars and rinse. Label, showing contents, engagement and lot number (if y'all canned more ane canner full that twenty-four hours).

Store in a clean, cool, night, dry place. The best temperature is between 50 and 70 °F. Avoid storing canned foods in a warm place near hot pipes, a range or a furnace, or in direct sunlight. They lose quality in a few weeks or months, depending on the temperature, and may even spoil. Continue canned goods dry out. Dampness may corrode metal lids and cause leakage so food will spoil. For best quality, apply canned foods within one year.

To Reprocess Food from Unsealed Jars

If you decide to reprocess food from jars that did not seal, do so within 24 hours. To do this, remove the chapeau and check the sealing surface on the jar for tiny nicks. Alter the jar if necessary, add together a new treated hat and reprocess using the same processing time. Label the jars of food that have been recanned and use these foods starting time. They volition be softer in texture and lower in nutritional value than food candy but once.

On Baby-sit Confronting Spoilage

Don't gustatory modality or use canned foods that show any sign of spoilage! Look closely at all jars before opening them. A bulging lid or leaking jar is a sign of spoilage. When you open up the jar, look for other signs such as spurting liquid and off-odor or mold. Spoiled canned foods should be discarded in a identify where they volition non exist eaten by humans or pets.

All suspect containers of spoiled, low-acid foods, including vegetables, meat, seafood and tomatoes, must be treated equally having produced botulinum toxin and handled carefully in 1 of two means:

  • If the jars or cans are still sealed, place them in a heavy garbage pocketbook. Shut and place the bag in a regular trash container or bury it in a nearby landfill.
  • If the jars or cans are unsealed, open or leaking, they should be detoxified earlier disposal.

Improperly canned, low-acid foods can contain the toxin that causes botulism without showing signs of spoilage. Jars of foods that accept not been properly processed must also be discarded, or if they are unsealed, open or leaking they must be detoxified and discarded as directed to a higher place even if there are no signs of spoilage. Low-acid foods are considered improperly canned if any of the post-obit are true:

  • The nutrient was not processed in a pressure canner.
  • The gauge of the canner was inaccurate.
  • Upwards-to-date researched processing times and pressures were not used for the size of the jar, style of pack or kind of food processed.
  • Proportions of ingredients were changed from the original approved recipe.
  • The processing fourth dimension and pressure level were not correct for the altitude at which the food was canned.

How to Detoxify Canned, Depression-Acrid Foods

Contact with botulinum toxin can be fatal whether information technology is ingested or enters through the pare. Exist extremely careful not to splash or come in contact with the doubtable food or liquid. Wear disposable prophylactic or heavy plastic gloves. Wear clothes and aprons that can be bleached or thrown out if contaminated.

Step-past-Step Instructions for Detoxification:

  • Carefully place the jars, with their lids, on their sides in an 8-quart, or larger pot or canner.
  • Wash your gloved hands thoroughly.
  • Carefully, without splashing, add together enough hot water to the pot to completely comprehend the jars with at least ane inch of water above the containers.
  • Place a lid on the pot and heat the h2o to boiling.
  • Boil for 30 minutes to make sure the food and containers are detoxified.
  • Cool and discard the containers, their lids and food in the trash or dispose in a nearby landfill.

How to Clean Upwards Contaminated Surfaces:

  • Wear prophylactic or heavy plastic gloves to clean upward contaminated work surfaces and equipment, including can openers and clothing that may have come in contact with doubtable foods or liquids.
  • Use a fresh solution of 1 role unscented, liquid, household, chlorine bleach (5 to six% sodium hypochlorite) to 5 parts clean water.
  • Spray or moisture contaminated surfaces with the bleach solution and let stand for 30 minutes. Avoid inhaling bleach or contact with skin.
  • Wipe treated spills with paper towels and place paper towels in a plastic bag before putting them in the trash.
  • Use the bleach solution to all surfaces and equipment over again, and permit represent 30 minutes and rinse.
  • Wash all detoxified counters, containers, equipment, clothing, etc.
  • Discard gloves when cleaning process is complete.

For more than information on canning foods at home, see HGIC 3020, Home Canning Equipment or HGIC 3000, Preserving Foods.

Sources:

  1. Reynolds, Susan and Paulette Williams. So Like shooting fish in a barrel to Preserve. Cooperative Extension Service, Academy of Georgia. Revised 2006 by Elizabeth Andress and Judy Harrison.
  2. USDA. 2009 Consummate Guide to Abode Canning.
  3. Blakeslee, K. 2015. How-To Guide To H2o Bathroom Canning and Steam Canning. Bachelor from: https://www.bookstore.ksre.ksu.edu/pubs/mf3241.pdf. Accessed February 22, 2019.
  4. Centers for Disease Control and Prevention (CDC). 2018. Protect Yourself from Botulism. Atlanta, GA: Centers for Disease Command and Prevention. Available from: https://www.cdc.gov/botulism/consumer.html. Accessed February 22, 2019.
  5. Harris, L.J., and Soule, K.E. 2017. Guidelines for Safe Canning of Acid Foods in a Steam Canner. Available from: https://anrcatalog.ucanr.edu/pdf/8573.pdf. Accessed February 22, 2019.
  6. Ingham, B. 2015. Guidelines of Using an Atmospheric Steam Canner for Home Food Preservation. Available from: https://extension.oregonstate.edu/sites/default/files/documents/8836/sp501004guidelines-atmosphericsteamcanner.pdf. Accessed February 22, 2019.
  7. National Center for Abode Food Preservation (NCHFP). 2015. Called-for Issue: Using Atmospheric Steam Canners. Athens, GA: National Centre for Dwelling Food Preservation. Available from: https://nchfp.uga.edu/publications/nchfp/factsheets/steam_canners.html. Accessed Feb 22, 2019.
  8. Willmore, P., Etzel, M., Andress, Eastward., and Ingham, B. 2015. Home Processing of Acid Foods in Atmospheric Steam and Boiling Water Canners. Food Protection Trends. 35(3): 150-160.

Document concluding updated on 01/20 by Sydney McKay.

Originally published 07/99