We just planted our tomatoes, eggplants and tomatillos this weekend. In a couple of more weeks we’ll be planting peppers, squash, cucumbers, melons, beans and corn. In just a few months we’ll be busy harvesting and preserving our bounty through drying, freezing and canning.
Preserving has been gaining in popularity and I see some really great recipes out there on the interwebs. I also see some dangerous ones that kind of scare me. I’ve seen so many bad ones, in fact, that I’ve decided that I’m no longer going to judge canned goods at events anymore unless the recipe and canning process is included with the sample. You can’t simply shoot from the hip and make up recipes that “sound about right” and expect for them to store at room temperature for extended lengths of time. There’s a science behind canning to ensure safety that I can’t stress enough. So I figured that with canning season fast approaching we should discuss some guidelines to canning to help everyone stay safe.
1. Just because it’s on the internet does not automatically make it a safe recipe.
Be critical of every recipe you see on the internet. Check to make sure it has enough acid and is processed long enough if it’s not pressure canned and uses low acid ingredients (especially if it is raw packed). If it’s high acid make sure it is water bath canned long enough. The USDA has safe canning guidelines through their National Center for Home Food Preservation site that you can cross reference from. Also avoid recipes that have dairy, eggs, and pureed low acid food (such as lemon curd, pumpkin butter and pureed bananas) and don’t also say that it is to only be kept in the refrigerator for a limited amount of time (usually for a month) or to freeze the finished product.
2. Books are *usually* a safe bet.
I only say “usually” because I’ve seen some questionable and downright dangerous recipes even in published books. Check the book to make sure it says the recipes have been tested for safety. The most reliably safe books (though I can’t testify to the flavor of all the recipes in these books) are:
- Ball Complete Book of Home Preserving
- Canning for a New Generation: Bold, Fresh Flavors for the Modern Pantry
- Put ’em Up!
- Food in Jars: Preserving in Small Batches Year-Round
- Complete Guide to Home Canning and Preserving (2009 Revision)
3. If you find a safe recipe do not alter it, but if you do, know the guidelines.
Even adding a bit more onion to a recipe can alter the pH enough to make it unsafe. For water bath canned products you want the pH to be 4.6 or lower. However, unless you have a super deluxe Vitamix blender, chances are just blending and using a litmus strip isn’t going to give you an accurate reading of the acidity. The safest way to test is to send it to a food lab, but that can get expensive so just stick with a tested recipe. Always follow the basic safe guidelines if you do change the recipe. If you’re not sure, err on the side of caution and don’t alter it. The canning recipes I have on this blog always follow the safe guidelines and I almost always increase the acid when I don’t need to just to be on the safe side. I will not post low-acid recipes that require pressure canning. And recipes that don’t follow the safe guidelines, like our oven-baked heirloom tomato sauce, will always be for eating immediately of freezing (which is why we don’t include canning instructions with it).
4. Not all fruit is created equal.
While many fruits are high acid and relatively easy to can, some are either borderline or low acid and must have acid added. Figs, bananas, white peaches, Asian pears, watermelon, mangoes and tomatoes all fall into this category of not acidic enough to can on their own without added acid. Be sure to follow the USDA guidelines if canning these items. I have posted tomato canning guidelines that are based on USDA guidelines and the Ball Complete Book of Home Preserving.
5. If it’s a low acid food and you don’t add acid don’t even think of water bath canning it (same goes for recipes with meat in them even if you do add acid).
I’m serious here. Botulism will fucking kill you. Adding loads of salt or sugar won’t save you here.
6. If a recipe says to pack pint jars don’t pack quart jars and increase the time to what you think it should be.
Sometimes you’ll come across recipes that only give you the processing time for a specific jar size. Don’t pack into larger jars because you don’t know what the processing time is for them to be safe. Tomato paste is a good example of this. Due to it’s consistency it’s best to only can it in 8 oz jars. And never can using jars larger than a quart unless the recipe calls for them (tomato juice can be canned in 1.5L jars per the Ball Complete Book of Home Preserving).
7. Don’t create shortcuts.
- Cut fruits or vegetables into the indicated size as this ensures that the center reaches the correct temperature and acidity if using low acid foods.
- Don’t “eyeball” the amounts of your ingredients – think of this as a science experiment rather than an art project.
- Start your processing time after the water has come back up to boiling if using a water bath canner or after you reach pressure when pressure canning.
- Pack hot food into hot jars that were slowly brought up to temperature, not cold jars (the sudden heat from the food will stress the glass causing breakage).
- Don’t reuse lids (Tattler lids are the exception). You can reuse rings though.
- Follow head space rules for a recipe – don’t over or under fill jars.
- Always make sure there is at least 1″ of water covering the jars when in the canner.
- Do not skip the water bath for acidic foods. The water bath heats up the food in the jar to kill microorganisms. The heated food increases in volume (why you need to follow rules for head space) pushing out air. The water covering the jars doesn’t allow air to reenter the jars. The air also is heated making it expand and escape the jar. Less oxygen means less oxidation and less spoilage (except for anaerobic microorganisms like Clostridium botulinum, many other microorganisms require oxygen). You’re much more likely to get mold if you don’t properly do a water bath. Mold changes the pH of the product making an acidic food more basic which opens it up to C. botulinum, which causes botulism.
- Remove air bubbles after packing hot jars. Sometimes the food can contain enough air in it to alter the head space. Plus extra air means extra oxygen and more chances for spoilage.
- Always wipe the rim with a clean cloth before putting the lid on. This will help ensure a good seal while also removing a vehicle for contamination to get inside the jar.
8. Take the rings off your jars after they seal.
The rings are really just designed to keep the lid on while canning and should be removed after they seal. This will help reduce corrosion and rust on your jars but more importantly removing the rings help you avoid a false seal. A failed seal would indicate spoilage but if the ring keeps the lid down you wouldn’t necessarily know the food has spoiled – smell, taste and looks can be deceiving for some types of spoilage. However, you can put the rings back on once you break the seal to avoid creating a mess.
9. Remember to adjust for altitude.
Find out your altitude and then adjust your canning time. Please note that the time difference may vary depending on the product you’re canning.
10. Use the right equipment.
Steam canners and oven canning are not recommended and cannot remove the risk of all types of spoilage. A stock pot that is deep enough for your jars plus 1″ of cover is fine for water bath canning. Make sure to use a rack on the bottom of your pot though. The rack helps keep water moving all the way around the jar and helps prevent the jars from breaking. Use a pressure canner, not a pressure cooker, when canning low acid foods and meat. Pressure cookers don’t have as reliable gauges if they have one at all. Also make sure that your pressure canner is in good condition. Old or poorly taken care of pressure cookers are dangerous and can explode. Your county extension can test your pressure canner for you or direct you to somewhere that can.
Canning isn’t something that should intimidate you by any means, you just have to follow some rules to make sure your finished product is safe. Properly canned foods are delicious and most times are much healthier than what you can purchase at the store. So get out there and start canning!
3 thoughts on “Canning Season is Almost Here – Stay Safe Out There”
Great post on an important topic. I spent a lot of time worrying about safe canning last year. My (French) neighbors can low acid foods like green beans by cooking them in a water bath for two hours. Two hours! And yet, they seem to have never heard of botulism, leaving me wondering if it’s just an American obsession. I decided not to test this idea but instead located resources to guide me. Among them, the new edition (75th anniversary edition) of The Joy of Cooking with it’s very good section on canning and strong emphasis on food safety. Also, I read on the USDA web site that boiling preserved foods for 10 minutes before eating them removes the toxins that cause botulism. That comforted me a bit, at least as far as tomato and tomato products were concerned. Finally, I have recently entered the wonderful world of fermentation preservation through the excellent book Wild Fermentations by Sandor Katz. Looking forward to some recipes from DIF.
Wow, great post! I became a certified Master Food Preserver because I wanted to learn to can the safe way and not fear that I was putting my family at risk. You covered every single point of canning safely and how important it is not to guess or ad lib. I also urge people to find their local Master Food Preserver group (through the UC Cooperative Extension) and attend the free public demonstrations on how to preserve safely.
Canning is rewarding and fun, but it’s important to follow the rules and only use safe, tested recipes from a trusted source. It’s not the same as cooking – where you can be as creative as you want!
Keep up the great work!
Hi Rachel, in addition to your comprehensive guide, I would suggest having a digital pH meter. We use one to test when canning things like salsa, especially when low acid ingredients have been added and you just want to make sure your recipe is safe. Here’s one example:
You need to also order the calibration solutions, then recalibrate before any critical (food) measurement. In addition to testing food, this tool lets you test pH of your soil, irrigation water, foliar fertilization sprays, etc.
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