Canning Soup? Watch Out for These Common Pitfalls – Lancaster Farming

The convenience of canned soup makes cooking and meal preparation easier on busy days. Ingredients and preparation techniques determine the safety of home-canned soup. Many food preservers would like to replicate soups found in the deli or supermarket. However, there are some commercially prepared foods that just cannot be reproduced safely by the home canner. Creamed soups are not suitable for home canning because their ingredients interfere with the proper transfer of heat during the processing step and can result in food-borne illness. Freezing soups with problem ingredients is a safer option.
Let’s look at some problem ingredients in home-canned soup. Flour and other thickening agents prevent heat from penetrating to the center of a jar and interfere with the destruction of bacterial spores that cause botulism. Never add thickening agents to a home-canned product before processing. Wait until you are ready to prepare the food for serving to add flour, cornstarch or other thickening agent. The only exception to this rule is when a scientifically research-tested recipe calls for Clear Jel, as in pie fillings or small amounts of thickener in a few relish recipes. So, the exception does not apply to soups.
Foods high in starch interfere with heat processing. That eliminates the use of noodles, alphabet noodles, spaghetti or other pasta, rice, barley, etc. in home-canned soups. Therefore, avoid canning chicken noodle soup, minestrone soup or beef barley soup. Add noodles or any type of pasta, rice or dumplings to canned soups or stews at serving time.
Butter, milk, cream cheese and other dairy products are low-acid foods that should never be added to home-canned soups before processing. Add butter and milk to soup just before serving.
We already eliminated condensed soups with thickeners and dairy products. But avoid canning a condensed vegetable or chicken corn soup. Only fill a jar half full of solids. Add broth or other hot liquid to fill jar, allowing 1-inch headspace. There needs to be space for the hot liquid to circulate between the particles of food.
Never can soup in half-gallon jars. The jars are too large for heat to be evenly distributed throughout the jar, and pressure canners are too shallow to accommodate the height of the jar. Also, there are no research-based protocols developed for using half-gallon jars for low-acid foods.
Thickened or cream of tomato soup should not be canned. Instead, can tomato juice, tomato vegetable juice blend or crushed tomatoes (without added vegetables). When you want to make the soup, open the jar of tomato product and add whatever seasoning vegetables and thickeners desired. A good cream of tomato soup is made by pouring the heated tomato mixture into a heated white sauce.
Other soups to avoid canning are pumpkin, winter squash, broccoli or cauliflower. These vegetables pack together and the soups contain ingredients that interfere with safe processing. There are not scientifically research-tested recipes for canning these soups. Instead, freeze them.
Vegetable soups in a broth base may be safely canned using the processing time for the ingredient that takes the longest process time as an individual ingredient. Sometimes a research-tested recipe will reduce this time. Most soups will take 60 to 90 minutes to process in a pressure canner depending upon jar size and ingredients.
Traditional vegetable soup can be safely canned. It is made with cut-up pieces or small vegetables in a broth base. Choose your favorite vegetables and prepare each as you would for a hot pack method if canned. Cooked meat or poultry without fat can also be added. If dried beans or peas are used, they must be rehydrated first. Combine the prepared vegetables, cooked meat, if desired, and enough hot water, broth, tomatoes or tomato juice to cover. Boil 5 minutes. Add salt to taste, if desired. Fill hot jars halfway with the solid (vegetable) mixture. Continue filling with hot liquid, leaving 1-inch of headspace. Remove air space. Wipe jar rims and adjust lids. Process pints for 60 minutes (or quarts for 75 minutes) in a dial-gauge pressure canner at 11 pounds pressure, or in a weighted-gauge pressure canner at 10 pounds pressure. If cooked seafood is added as part of the solid mixture, processing time must be 100 minutes. Adjust pressure for higher altitudes.
If you have food preservation questions, a home economist is available to answer questions on Wednesdays from 10 a.m. to 2 p.m., by calling 717-394-6851 or writing Penn State Extension, Lancaster County, 1383 Arcadia Rd., Room 140, Lancaster, PA 17601.
The Well Preserved news column is prepared by Penn State Extension.
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