Can Cream of Mushroom Soup? A Comprehensive Guide
Yes, cream of mushroom soup can be canned, but it requires specific procedures using a pressure canner to ensure safety. Water bath canning is not recommended due to the low acidity of the ingredients.
Understanding the Risks: Low-Acid Foods and Botulism
Canning is a fantastic way to preserve food and enjoy homemade goodness year-round. However, it’s crucial to understand the science behind it, especially when dealing with low-acid foods like cream of mushroom soup. The primary concern is Clostridium botulinum, the bacteria that produces the deadly botulism toxin. This bacteria thrives in low-oxygen, low-acid environments, exactly the conditions found in improperly canned foods. Therefore, cream of mushroom soup, containing mushrooms and potentially dairy (even if powdered), falls squarely into the low-acid category.
Why Pressure Canning is Essential
Water bath canning, ideal for high-acid foods like jams and pickles, doesn’t reach a high enough temperature to kill Clostridium botulinum spores. Pressure canning, on the other hand, uses steam under pressure to achieve temperatures of 240°F (116°C) or higher, which is sufficient to eliminate these spores. This makes pressure canning the only safe method for preserving cream of mushroom soup at home.
The Canning Process: Step-by-Step
While recipes vary, the general process for canning cream of mushroom soup involves these steps:
- Prepare Jars: Sterilize canning jars and lids according to manufacturer instructions. This typically involves boiling them in water.
- Sauté Aromatics: Sauté finely chopped onions and garlic in butter or oil.
- Cook Mushrooms: Add sliced or chopped mushrooms and cook until softened.
- Create a Roux: Melt butter in a separate saucepan and whisk in flour to form a roux. Cook for a minute or two to remove the raw flour taste.
- Add Broth and Milk (or powdered milk): Gradually whisk in chicken or vegetable broth, ensuring no lumps form. If using powdered milk, whisk it in with the flour when making the roux. Add fresh milk later, at serving time after re-heating.
- Combine and Simmer: Add the mushroom mixture to the broth mixture and simmer until slightly thickened, stirring frequently. Season with salt, pepper, and other desired spices.
- Fill Jars: Ladle the hot soup into sterilized jars, leaving the recommended headspace (usually 1 inch).
- Remove Air Bubbles: Run a non-metallic spatula or bubble remover tool along the inside of the jar to release any trapped air bubbles.
- Wipe Rims: Clean the jar rims with a damp cloth to ensure a proper seal.
- Apply Lids and Rings: Place sterilized lids on the jars and screw on the rings fingertip-tight.
- Process in Pressure Canner: Follow the specific pressure canning instructions for your canner and altitude, typically for 75 minutes (pints) or 90 minutes (quarts) at 10 pounds of pressure. Always consult your canner’s manual.
- Cool and Check Seals: Allow the jars to cool completely. Check for proper seals by pressing down on the center of each lid. A properly sealed lid will be concave and won’t flex.
Important Considerations and Safety Tips
- Acidity: Be aware that some commercially canned soups contain added acids (like citric acid) to make them safe for water bath canning. Homemade soup lacks this safeguard.
- Dairy: Using powdered milk during the canning process is generally considered safer than using fresh milk. Add fresh milk after opening and reheating the soup. If you choose to use any fresh dairy in your soup during the canning process, be sure to consult a trusted canning guide (such as the USDA Complete Guide to Home Canning).
- Headspace: Leaving the correct amount of headspace is critical for proper sealing. Too little headspace can cause the soup to boil over during processing, while too much can prevent a vacuum from forming.
- Altitude Adjustment: Adjust processing time or pressure based on your altitude. Higher altitudes require longer processing times or higher pressure because water boils at a lower temperature.
- Storage: Store canned soup in a cool, dark, and dry place. Properly canned soup can last for a year or longer.
- Inspect Before Use: Before opening a jar, inspect the lid for any signs of bulging, rust, or damage. If the lid is bulging or there’s any sign of spoilage, discard the soup without tasting it.
Common Mistakes to Avoid
- Under-Processing: Insufficient processing time or pressure can lead to botulism poisoning.
- Overfilling Jars: Leaving too little headspace can cause jars to explode during processing or prevent proper sealing.
- Using Unreliable Recipes: Always use tested and approved recipes from reputable sources like the USDA or university extension services. Avoid using outdated or unverified recipes.
- Not Adjusting for Altitude: Failing to adjust processing time or pressure for altitude can result in under-processing.
- Using Damaged Jars or Lids: Always inspect jars and lids for cracks, chips, or damage before use.
Frequently Asked Questions (FAQs)
Is it safe to can cream of mushroom soup with fresh milk or cream?
It’s generally not recommended to use fresh milk or cream directly in cream of mushroom soup when canning. While some sources suggest using powdered milk added during the canning process, fresh dairy can compromise the safety and quality of the canned product. Add the fresh milk or cream after opening and reheating the soup.
Can I can cream of mushroom soup in a water bath canner?
No, absolutely not. Due to the low acidity of the soup’s ingredients, water bath canning is not a safe method for preserving cream of mushroom soup. Pressure canning is the only safe option.
What happens if I don’t have a pressure canner?
If you don’t have a pressure canner, you should freeze the soup instead of canning it. Alternatively, consider making smaller batches to consume immediately or within a few days.
What kind of mushrooms are best for canning?
Button mushrooms, cremini mushrooms, or a blend of wild mushrooms can be used. Ensure they are fresh and of good quality. Avoid using mushrooms that are bruised or starting to spoil.
How long does canned cream of mushroom soup last?
Properly canned cream of mushroom soup can last for a year or longer when stored in a cool, dark, and dry place. However, it’s always best to use it within a year for optimal flavor and quality.
How do I know if my canned soup has spoiled?
Look for signs of spoilage such as a bulging lid, leaks, off odors, or unusual colors. If you notice any of these signs, discard the soup immediately without tasting it. Remember, botulism toxin is odorless and tasteless.
Can I adjust the seasoning in the recipe?
Yes, you can adjust the seasoning to your taste. However, be cautious about adding ingredients that may affect the soup’s acidity or density. It’s best to stick to safe and tested recipes.
What if I can’t find a tested recipe for cream of mushroom soup?
If you can’t find a specific tested recipe, adapt a tested recipe for a similar vegetable soup and modify it to include mushrooms. You can find tested recipes at your local extension office, or on the websites of trusted sources, like the USDA. Never improvise canning recipes without proper knowledge.
Do I need to sterilize the jars and lids?
Yes, it’s essential to sterilize the jars and lids to kill any bacteria that might be present. Follow the manufacturer’s instructions for sterilizing jars and lids. This usually involves boiling them in water.
What’s the correct headspace for canning cream of mushroom soup?
Generally, a headspace of 1 inch is recommended for canning cream of mushroom soup. Refer to your canning recipe and canner’s manual for specific instructions.
How do I adjust the processing time for altitude?
Altitude adjustments are crucial for safe canning. Consult your pressure canner’s manual or the USDA Complete Guide to Home Canning for specific altitude adjustment guidelines. These resources will tell you how to increase the pressure or the processing time.
What should I do if a jar doesn’t seal properly?
If a jar doesn’t seal within 24 hours, you have a few options: you can either reprocess the soup using a new lid within the recommended processing time, or you can refrigerate the soup and consume it within a few days. Freezing the soup is also an option. Do not store a unsealed jar at room temperature.