10 Foods You Should Avoid Canning

Published in Food and Wine on Monday, July 28th 2025 at 11:07 GMT by Chowhound
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While canning at home can be a great hobby to take up, there are some foods you should definitely avoid canning yourself so you don't get sick or hurt.

The Perils of Home Canning: 10 Foods You Should Never Attempt to Preserve in Jars

Home canning has surged in popularity in recent years, offering a satisfying way to preserve seasonal bounty, reduce food waste, and create homemade gifts. From tangy pickles to sweet jams, the process allows us to capture the essence of fresh produce for months on end. However, not all foods are suitable for this time-honored preservation method. Canning involves sealing food in airtight jars and heating them to destroy harmful microorganisms, but certain items pose significant risks due to their composition, pH levels, or how they interact with the canning environment. Botulism, a potentially deadly form of food poisoning caused by the Clostridium botulinum bacterium, is a primary concern, thriving in low-oxygen, low-acid conditions that canning can inadvertently create if not done correctly.

The key to safe canning lies in understanding acidity and processing methods. High-acid foods like fruits and tomatoes can often be water-bath canned, while low-acid items require pressure canning to reach temperatures high enough to kill spores. But even with the right equipment, some foods simply don't belong in jars. Drawing from expert guidelines from sources like the USDA and food safety organizations, this article explores 10 foods you should avoid canning at home. We'll delve into why each is problematic, the potential dangers, and safer alternatives to satisfy your preservation urges.

1. Dairy Products: A Recipe for Spoilage and Safety Hazards

Dairy items such as milk, cheese, butter, and cream are among the top foods to steer clear of when canning. These products are highly perishable and don't respond well to the heat processing required for safe preservation. Milk, for instance, can separate and curdle during heating, leading to an unappetizing texture. More critically, dairy's low acidity makes it a breeding ground for bacteria, including those that produce botulism toxins. Attempting to can butter or cheese spreads can result in rancidity or uneven heating, where pockets of the product remain underprocessed.

Instead of canning, consider freezing dairy for longer storage. Milk can be frozen in portions, and butter keeps well in the freezer for up to a year. For cheese, vacuum-sealing and refrigerating is often sufficient. If you're keen on preserved dairy flavors, explore fermented options like yogurt-making, which doesn't involve the risks of canning.

2. Eggs: Fragile Proteins That Don't Preserve Well

Eggs in any form—whole, pickled, or as part of a recipe—should never be home-canned. The proteins in eggs denature and become rubbery under high heat, ruining the texture. Safety-wise, eggs are low-acid and can harbor salmonella or other pathogens that aren't reliably eliminated without commercial-grade equipment. Canned eggs have been linked to outbreaks of foodborne illness in the past, prompting strict warnings from health authorities.

A better approach is pickling eggs in vinegar-based brines and storing them in the refrigerator, where they'll last for weeks. For long-term preservation, dehydration or freezing scrambled eggs works, but always prioritize food safety testing if experimenting.

3. Pureed or Mashed Foods: Density Issues Lead to Uneven Heating

Foods like pumpkin butter, mashed potatoes, or pureed soups are notoriously difficult to can safely. Their thick consistency prevents heat from penetrating evenly, creating "cold spots" where bacteria can survive. The USDA explicitly advises against canning pureed pumpkin due to its density and low acidity, which heightens botulism risks. Similarly, mashed vegetables can change in viscosity during processing, making it hard to ensure sterilization.

Opt for freezing these items instead. Pureed fruits and veggies freeze beautifully in ice cube trays for easy portioning. If you love spreads, make small batches of fruit butters and refrigerate them for short-term use.

4. Oils and Fats: Separation and Rancidity Risks

Pure oils, infused oils, or high-fat items like lard shouldn't be canned. Oils don't mix well with water-based canning liquids and can separate, leading to improper sealing or spoilage. Fats can also turn rancid over time, and their presence interferes with the vacuum seal necessary for safety. Infused oils, popular for gourmet gifts, are particularly risky as botulism spores can grow in the anaerobic environment.

Store oils in cool, dark pantries or refrigerate them. For flavored options, create small batches of herb-infused vinegars, which are safer to can due to their acidity.

5. Low-Acid Vegetables Without Pressure Canning: A Botulism Hotbed

While many vegetables can be canned, low-acid ones like green beans, carrots, and corn require pressure canning to be safe. Attempting to water-bath can them is a grave mistake, as it doesn't reach the 240°F needed to kill botulism spores. Even with pressure canning, overpacking jars or improper venting can lead to failures.

Always follow tested recipes from reliable sources. If pressure canning isn't an option, pickle these veggies in acidic brines or freeze them for preservation.

6. Meats and Poultry: High Stakes for Protein Preservation

Home canning meats like beef, chicken, or fish demands precise pressure canning to avoid contamination. Without it, these low-acid proteins can foster bacterial growth. Texture degradation is another issue—canned meats often become mushy or dry. Commercial canning uses additives and strict controls that home setups can't replicate.

For safer meat preservation, try smoking, dehydrating (for jerky), or freezing. Cured meats like bacon can be refrigerated or frozen effectively.

7. Pasta and Rice: Starch Expansion and Safety Concerns

Canning cooked pasta or rice is ill-advised because starches absorb liquid and expand, potentially causing jars to break or seals to fail. These grains are also low-acid and can create an environment conducive to bacterial proliferation if not heated thoroughly.

Prepare pasta and rice fresh, or dry them for long-term storage. Freezing cooked versions in meal-sized portions is a practical alternative.

8. Thickened Soups and Stews: Viscosity and Heat Penetration Problems

Soups thickened with flour, cornstarch, or other agents shouldn't be canned, as thickeners prevent even heat distribution. This can lead to underprocessed areas prone to spoilage. The USDA recommends canning clear broths and adding thickeners later.

Freeze soups in containers, or can base ingredients separately and combine them when reheating.

9. Certain Fruits and Berries: Texture and Quality Degradation

While many fruits are ideal for canning, delicate ones like bananas, avocados, or overripe berries can turn to mush or discolor. Bananas, for example, have enzymes that cause browning and aren't acidic enough for safe water-bath canning without additives.

Dehydrate or freeze these fruits. Banana chips or frozen berry purees maintain quality better.

10. Recipes with Flour or Cornstarch: Binding Agents That Bind Trouble

Any recipe incorporating flour or cornstarch as a thickener, such as gravies or pie fillings, is unsafe for canning. These ingredients alter the food's density, impeding heat transfer and increasing botulism risks.

Use clear jel, a modified cornstarch approved for canning, or avoid thickening altogether until serving time.

In conclusion, while home canning is a rewarding skill, it's crucial to prioritize safety over experimentation. Always use up-to-date guidelines from the National Center for Home Food Preservation or similar authorities, invest in quality equipment like pressure canners, and test your seals rigorously. If in doubt, err on the side of caution—freezing, dehydrating, or refrigerating are often simpler, safer methods for preserving tricky foods. By avoiding these 10 problematic items, you can enjoy the fruits of your labor without the shadow of foodborne illness. Remember, the goal of preservation is not just longevity but also edibility and health. Happy (and safe) preserving!

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