Confused about home canning?

Dec 16, 2023

Canning is an excellent way to preserve home grown fruits and vegetables. If you are confused about whether you should to raw pack or hot pack your garden produce to safely preserve it for later this year, the Nebraska Extension has compiled the following information to provide clarity on which method is the best for preserving the fruits of your labor.

Raw pack

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 air in and around the food may cause discoloration within two to three months of storage. Raw packing is more suitable for vegetables processed in a pressure canner.

Hot pack

Hot packing is the practice of heating freshly prepared food to boiling, simmering it for 2 to 5 minutes and promptly filling jars loosely with the boiled food. This practice helps remove air from food tissues, shrinks food, helps keep the food from floating in the jars, increases vacuum in sealed jars and improves shelf life. Preshrinking food permits filling more food into each jar. Hot packing is the preferred method for foods processed in a boiling water canner.

At first, the color of hot packed foods may appear no better than that of raw packed foods, but within a short storage period, both color and flavor of hot packed foods will be superior.

Whether food has been hot packed or raw packed, the juice, syrup or water to be added to the foods should be heated to boiling before adding it to the jars.

Headspace

The unfilled space above the food in a jar and below the lid is termed headspace. This space is needed for expansion of food as jars are processed, and for forming a vacuum in cooled jars. The extent of expansion is determined by the air content in the food and by the processing temperature. Air will expand more than food will when heated to high temperatures. The higher the temperature, the greater the expansion. Pressure canned foods require a larger headspace than foods heated in a boiling water canner, because pressure canned foods are heated to a higher temperature.

For correct headspace for the food you are processing, use an up to date, research tested recipe or check the Nebraska Extension food website. Fill jars with food and add liquid to cover food, leaving appropriate headspace. Release air bubbles by inserting a flat plastic (not metal) spatula between the food and the jar. Slowly turn the jar and move the spatula up and down to allow air bubbles to escape. Add additional liquid, if needed, to obtain the proper headspace. Clean the jar rim with a dampened paper towel. Place the lid, gasket down, onto the cleaned jar rim and fit the metal screw band over the flat lid. An uncleaned jar rim may cause seal failure. Follow the manufacturer’s guidelines for tightening the jar lids properly. Overtightened lids may buckle or cause the lid not to seal properly. Process as directed in an up to date, research tested recipe for your specific food or check the Extension food website.

After processing

Do not retighten lid ring bands or push down on the center of the flat metal lid after processing jars. As jars cool, the contents contract, pulling the self-sealing lid firmly against the jar to form a high vacuum seal. Cool the jars at room temperature for 12 to 24 hours. Jars may be cooled on racks or towels. The food level and liquid volume of raw packed jars will be noticeably lower after cooling. Air is exhausted during processing and food shrinks. If a jar loses excessive liquid during processing, do not open it to add more liquid. After jars have cooled, check for sealed lids by following one of these three methods:

Press the middle of the lid with a finger or thumb. If the lid springs up when you release your finger, the lid is not sealed.

Tap the lid with the bottom of a teaspoon. If it makes a dull sound, the lid is not sealed. If food is in contact with the underside of the lid, it will also cause a dull sound. If the jar is sealed correctly, it will make a ringing, high pitched sound.

Hold the jar at eye level and look across the lid. The lid should be concave (curved slightly down in the center). If the center of the lid is either flat or bulging, it may not be sealed.

Screw bands should be removed after jars are cooled. Wash, dry and store screw bands for future use. If left on stored jars, screw bands may become difficult to remove, often rust and may not be reusable. Before storing jars, wipe them with a clean, damp cloth. To remove mineral deposits, use a cloth that has been dipped in a solution containing 1 cup vinegar per gallon of water.

For more information food preservation questions, go to food.unl.edu.

Most white and cider vinegars used for making pickles and salsa are 5% acidity, but not all. An acidity level below 5% is not recommended as it is not adequate to control microbial growth and may result in spoilage.

The two most common vinegars are apple cider vinegar and distilled white vinegar.

Cider vinegar is derived from apples and is light golden in color with a tart fruit flavor. It has a milder flavor than distilled white vinegar. Because of its color, it may darken light colored fruits and vegetables.

Distilled white vinegar is a clear, colorless liquid derived from grain alcohol that has a sharp, pungent flavor. White vinegar is preferred when a light color is desired for making fruit or cauliflower pickles. It does not compete with the distinctive flavors of herbs and spices in brine. Because it is clear, it does not change the color of light colored fruits and vegetables.

If your research-tested recipe does not specify a particular type of vinegar, you may safely use either white or cider vinegar if it is labeled as 5% acidity.

Specialty vinegars include red or white wine vinegar, malt vinegar, balsamic and other flavored vinegars. Use these only when specified in a research-tested recipe.

The standard vinegar used in home canning must have 5% acidity, and when pickling it’s important to use a vinegar with 5% acidity. Anything less than 5% is not safe to use, as it may not be strong enough to ensure the safety of canned products. It’s recommended that you always check the vinegar label for its acidity level.

If you have used vinegar with lower acidity (less than 5%) in your canned food products and you followed a research-tested recipe, the National Center for Home Food Preservation recommend considering the following:

If your canned food has been preserved for less than 24 hours using 4% vinegar, it is advisable to store the jars in the refrigerator to maintain the safety and quality of the product.

If your canned food has been preserved for more than 24 hours using 4% vinegar, it is advised to discard the product.

Here are some other canning tips:

Do not dilute the vinegar with water unless it specifically says so in a research-tested recipe.

Do not reuse leftover pickle juice in which vegetables or fruit have been cooked before being packed into jars. It is safe to use leftover pickle brine that has not contained any food product.

Do not use homemade vinegar when pickling. The acidity of homemade vinegar is not consistent.

Some balsamic or sherry vinegars are 6%-7% acidity. Stay in the range of 5%-7% acidity for home food preservation.

Do not use cleaning vinegars or horticultural vinegars. These are extremely high in acid (11%-30%), one is 75% acidity. These are not intended for food preservation.

Remember that ensuring the safety of your home-canned products is of utmost importance. Following tested and approved recipes, including the use of recommended vinegar acidity, is crucial for maintaining the safety and integrity of the preserved foods.

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