Canning Vegetables

Preserving food at home can be a rewarding experience that provides year-round access to seasonal produce. Using tested recipes, following preparation instructions, making necessary high elevation processing adjustments, and maintaining equipment are all important for insuring the safety and quality of home preserved foods. 

With renewed interest in locally-grown foods, home gardening, and food preservation, it’s important to protect yourself and your family by following safe canning methods.

• Home canned vegetables, which are low-acid foods, must be processed in a pressure canner to supply sufficient heat (240° F) to destroy botulism-causing bacteria. Failure to properly process low-acid foods in a pressure canner can allow the survival of Clostridium botulinum spores and subsequently toxin that can cause severe illness or death. 
• Always use tested recipes/instructions and process at the number of pounds and specified time for your elevation. Do not take short cuts in recommended preparation or processing procedures! 
• Use CSU Extension’s free Preserve Smart website for 24/7 access to tested home food preservation recipes and instructions for over 55 fruits and vegetables! 

Figure 1: Canning jars and lids

A. Narrow metal screw band.  

B. Metal lid with sealing compound.  

C. Canning jar seal area. 

Equipment and Jars

• Pressure canner. Make sure your pressure canner has a tight-fitting cover, a removable rack, clean exhaust vent (or petcock) and safety valve, and an accurate pressure gauge. Replace a cracked or worn gasket to prevent water leakage and pressure loss. 
• The intense heat of pressure canning can cause the gasket to shrink over time, allowing air and steam to escape under the lid. 
• Use a pressure canner that holds at least 4 quart jars. 
• Electric multi-cookers and smaller stovetop pressure cookers should NOT be used for home food preservation because they cannot ensure adequate temperature and heat penetration within the jars. 

Pressure canners can have one of two types of gauges: 

• Weighted gauge – an instrument that is used to both indicate and regulate pressure. The weight should ‘jiggle’ several times a minute and/or keep rocking gently to maintain the desired processing pressure. 
  • Weighted gauges should be cleaned before each use. 

• Dial gauge – an instrument designed to indicate the pressure within the canner. 
  • Dial gauges should be checked annually for accuracy which is best done in advance of canning season each year. Contact your local Extension office for more information about dial gauge testing. 

Canning Jars. Discard any jars with cracks or chips since defects can prevent an airtight seal. 

• Use jars designed specifically for home canning. 
  • Do not use jars that are cracked or have any sort of damage (i.e. chipped) on the top edge. 

• When canning vegetables, use only pint and quart jars, and then only the size recommended within the tested recipe. 
  • Do not use commercial food jars (mayonnaise, pasta sauce, etc.) as they are not heat-tempered and can break easily and/or not seal properly when pressure canned. 
• Wash jars in hot, soapy water and rinse well before using. Keep the jars hot until they are filled and placed in the canner to help prevent jar breakage. 

Lids and Screw Bands (two-piece set). Discard any screw bands with dents or rust, since defects can prevent an airtight seal. 

• Prepare new/unused flat metal lids as directed by the manufacturer. 
  • Lids are designed for single-use, and should NOT be used for home canning more than once! 
• Screw bands can be cleaned and used multiple times. Store carefully to prevent rusting or denting. 

NOTE: One-piece home canning lids have not been researched for safe home food preservation, and are therefore not recommended. 

Other Useful Canning Tools: 

• Air bubble remover, plastic knife, or non-metallic spatula- used to release air bubbles from within the jar 
• Canning funnel- funnel made from metal or food-grade plastic with wide, short neck for filling jars 
• Headspace ruler- special graduated utensil or plastic ruler for measuring required space at the top of a filled jar 
• Jar lifter- used to safely move jars to and from hot water during the canning process 
• Magnetic lid wand- helps transfer metal lids to top of jars and prevent contamination 
• Timer- necessary for critical timed steps throughout the canning process 

Prepare Vegetables

• Select fresh, ripe vegetables for canning. The sooner from harvest to jar, the better. 
• Handle produce gently to avoid bruising. 
• Wash all vegetables thoroughly. 
• Avoid soaking vegetables as it may cause loss of flavor and nutrients. 
• Prepare as specified in a tested recipe (size of pieces, peeled, etc.). See individual directions in Table 1. 

Fill Jars

There are two approved packing methods available for safely canning vegetables. Depending on the method used, both the vegetable preparation and the approved jar size for that method need to be noted before beginning the canning process. (For example, some vegetables cannot be safely canned in quart jars.) 

• The hot-pack method is preferred for all low-acid foods, including vegetables. 
  • Heat prepared vegetables in water or steam as directed by recipe before packing. 
  • Loosely pack jars with prepared vegetables and cover with the boiling cooking liquid or water. 

• Some vegetables can be safely processed using the raw-pack method if indicated by a tested recipe. (See individual vegetable canning directions in Table 1 to determine which method to use.) 
  • Add prepared, raw vegetables to jars and cover with boiling water. 
    • Firmly pack most raw vegetables (except starchy ones) into the jars. 
    • Loosely pack starchy vegetables, such as corn, peas, and lima beans, because they expand during processing. 

For both hot- and raw-pack: 

• Salt may be added to each jar, if desired. Salt is added only for seasoning and does not help preserve the food. If salt is used, canning salt is recommended to prevent the liquid from turning cloudy. Use 1/2 tsp salt per pint/1 tsp per quart jar. 
• Remove trapped air bubbles by inserting a plastic knife or non-metallic bubble remover between the food and the jar. Slowly turn the jar and move the tool up and down to allow air bubbles to escape. 
• Read the directions for each vegetable for the amount of space to leave between the top of the food and the top of the jar (headspace). 
  • This headspace is important to obtain a good seal and allow for expansion of the jar contents. 
  • Measure headspace and add or remove liquid, as necessary. 
• Wipe the jar rim with a clean damp paper towel to remove any food particles. 
• Place prepared lid on the jar. Screw on the band until fingertip tight. Avoid over-tightening! 
  • It is necessary for air inside the jars to be forced out from under the lids during the canning process, creating a vacuum and a proper seal.