So, you’ve got a garden bursting with ripe, juicy tomatoes, and you’re itching to preserve that summer goodness for the colder months. That’s amazing! But then you stumble upon a question that leaves you scratching your head: Do you *really* have to use lemon juice when canning tomatoes?
Well, the short answer is a resounding yes!. But let’s dive deeper into why this seemingly simple step is so crucial for safe and delicious home-canned tomatoes.
Why Acidify Tomatoes When Canning?
Tomatoes are a borderline high-acid food, meaning their natural acidity might not be enough to prevent the growth of harmful bacteria during the canning process. Over time, tomato varieties have evolved, and many now have a milder flavor and lower acidity than their predecessors. Testing has revealed that some modern tomato varieties have pH values at or above 4.6, and some even reach pH 5 or higher. A pH of 4.6 is the danger zone. Above this level, nasty bacteria like *Clostridium botulinum* can thrive, producing a deadly toxin that causes botulism.
Adding lemon juice (or another acid) lowers the pH of all tested tomato varieties enough to allow for safe processing in a water bath canner. Acidifying all whole, crushed, or juiced tomatoes is recommended to ensure the safety of the canned product after processing. This applies whether you’re using a water bath canner or a pressure canner.
The Science Behind the Acidity
Acidity, measured by pH, is a critical factor in food preservation. Microorganisms have different pH ranges in which they can grow. By increasing the acidity, we create an environment where these harmful bugs can’t survive.
*Clostridium botulinum*, the culprit behind botulism, cannot grow in high-acid environments. So, by acidifying our tomatoes, we’re essentially creating a hostile environment for this dangerous bacterium.
How to Acidify Your Tomatoes
The acidification process is straightforward. Here’s what you need to know:
- What to use: Bottled lemon juice or citric acid.
- How much to use: For quarts, add 2 tablespoons of bottled lemon juice or ½ teaspoon of citric acid. For pints, use 1 tablespoon of bottled lemon juice or ¼ teaspoon of citric acid.
- When to add: You can add the lemon juice directly to the jars before filling them with the tomato product, or you can add it after filling. Just ensure the correct amount goes into each jar.
Why Bottled Lemon Juice?
It’s crucial to use bottled lemon juice rather than freshly squeezed. Bottled lemon juice has a standardized acidity level, while the acidity of fresh-squeezed juice can vary, making it unreliable for canning. Lakewood Organic Pure Lemon Juice is a great option because it has a consistent 5% acidity.
Citric Acid: The Flavor-Neutral Alternative
If you’re not a fan of the lemon flavor, citric acid is an excellent alternative. It’s a flavorless powder that increases acidity without altering the taste of your tomatoes. You can find it in the spice aisle of most grocery stores or online.
Can You Use Vinegar Instead of Lemon Juice?
While some older recipes may call for vinegar, bottled lemon juice or citric acid are better choices. Vinegar has a stronger flavor that can sometimes overpower the taste of the tomatoes. If you do opt for vinegar, make sure to use a 5% acidity vinegar and follow a tested recipe.
Debunking Common Myths
- Myth #1: “My grandmother never used lemon juice, and her tomatoes were fine.” Canning recommendations have evolved. Older methods may not meet today’s safety standards. It’s always best to follow current, research-based recipes.
- Myth #2: “I only use low-acid tomatoes, so I don’t need to add lemon juice.” Even low-acid tomatoes need to be acidified to ensure safety. The natural sweetness of these varieties can mask their acidity, so it’s essential to follow the same acidification directions as you would for regular tomatoes.
- Myth #3: “If the jar seals, it’s safe.” A sealed jar indicates a vacuum, but it doesn’t guarantee the absence of harmful bacteria. Adequate processing time and proper acidification are crucial for eliminating these microorganisms.
The Right Way to Can Tomatoes
- Choose high-quality tomatoes: Avoid tomatoes from dead or frost-killed vines, as they may be lower in acidity and more likely to harbor bacteria.
- Wash and prepare your tomatoes: Wash the tomatoes thoroughly and remove any blemishes or bruises.
- Follow a tested recipe: Use a current, research-based recipe from a reliable source, such as the USDA Complete Guide to Home Canning, the Ball Blue Book, or a local extension office.
- Acidify: Add the correct amount of bottled lemon juice or citric acid to each jar.
- Process: Process the jars in a boiling water bath canner for the recommended time, adjusting for your altitude.
- Cool and check seals: Let the jars cool completely and check that they’ve sealed properly. The lids should be concave and not flex when pressed.
What If You Forget the Lemon Juice?
If you realize you forgot to add lemon juice after processing your tomatoes, it’s best to err on the side of caution. The safest option is to discard the jars. While it’s heartbreaking to waste your hard work, it’s not worth risking your health.
If you’ve only just started processing and realize your mistake, you can stop the process, add the lemon juice, and reprocess the jars for the full recommended time.
Adding Sugar: Balancing the Flavor
While you can add sugar to offset an acidic taste, don’t reduce the amount of acid prior to canning. Sugar is added after opening the jars that have been processed and sealed, if desired.
Don’t rely on the open-kettle method
Do not can using the open kettle method. Heating the tomatoes or tomato product and pouring the hot product into the jars, adding the lids, and waiting for the lids to “pop” without any further processing is unsafe. Even though the jars may seal, the contents inside the jars have not been heated adequately to destroy harmful spoilage organisms.
Final Thoughts
Canning tomatoes is a rewarding way to preserve the flavors of summer. By understanding the importance of acidification and following tested recipes, you can enjoy safe, delicious, home-canned tomatoes all year round. So go ahead, grab those tomatoes, and get canning.