Home canning tomatoes is a fantastic way to preserve the taste of summer and enjoy delicious, homemade goodness all year round. But, to ensure your canned tomatoes are safe to eat, understanding the importance of acidity and how much lemon juice to add is crucial. This guide will walk you through everything you need to know about acidifying your home-canned tomatoes using lemon juice, ensuring a safe and delicious final product.
Why is Lemon Juice Necessary When Canning Tomatoes?
Tomatoes are considered a borderline high-acid food, meaning their natural acidity is sometimes insufficient to prevent the growth of harmful bacteria, specifically *Clostridium botulinum*, which causes botulism. Over the years, tomato varieties have evolved, with many modern types exhibiting milder flavors and lower acidity than their predecessors. Testing has revealed that some current 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 threshold for preventing botulism.
Adding lemon juice (or citric acid) lowers the pH of all tested tomato varieties enough to allow for safe water bath canning. Acidifying all whole, crushed, or juiced tomatoes is now recommended because this ensures the safety of the canned product after processing in a water bath canner. This acidification step is necessary whether you’re using a water bath canner or a pressure canner.
How Much Lemon Juice Should You Add?
The general recommendation for acidifying tomatoes is to add bottled lemon juice or citric acid to each jar before processing. Here’s the breakdown:
- For quarts: Add 2 tablespoons of bottled lemon juice or ½ teaspoon of citric acid per quart of tomatoes.
- For pints: Use 1 tablespoon of bottled lemon juice or ¼ teaspoon of citric acid per pint of tomatoes.
You can add the bottled lemon juice directly to the jars before filling them with the tomato product or after filling. Just ensure you add the lemon juice to each jar and follow the recommended amounts precisely.
Important Considerations When Using Lemon Juice
- Use Bottled Lemon Juice: It is crucial to use bottled lemon juice rather than freshly squeezed lemon juice. Bottled lemon juice has a standardized acidity level, while fresh-squeezed juice has varying levels, making it unreliable for consistent acidification. Commercial lemon juice is required to have a certain pH, ensuring that your tomatoes are acidic enough.
- Don’t Reduce Acid: Although you may add sugar to offset an acidic taste after opening the jars, you cannot decrease the acid before canning. The acidity is crucial for safety and cannot be compromised.
- Mix it Up: When filling your jars, leave a 1/2-inch headspace. Then fill the jar half to three-fourths full with tomatoes, and gently press on the tomatoes to release the juice and fill all the space between the tomatoes. Continue filling and gently pressing until the contents of the jar are within 1/2 inch of the top rim.
Step-by-Step Guide to Canning Tomato Juice
Canning tomato juice is a simple process. Here’s a step-by-step guide to help you through it:
Equipment You’ll Need:
- Dishpan or containers
- Knife
- Large kettle
- Long spoon
- Ladle
- Food Mill, Victorio Strainer, or blender and strainer
- Wide Funnel
- Damp cloth
- Small pan
- Fork or lid wand
- Water bath canner
- Canning jars with lids and bands
- Jar lifter
- Old towels or rags
Ingredients:
- Fresh tomatoes (approximately 23 lb of tomatoes makes 7 quarts of juice)
- Salt (optional)
- Bottled lemon juice or citric acid
Instructions:
- Wash the Tomatoes: Thoroughly wash the tomatoes and cut out the stem and any blemishes. There is no need to peel the tomatoes.
- Cook the Tomatoes: Cut the tomatoes into chunks and put them into a large kettle. Squish a few tomatoes to create some juice so the tomatoes don’t stick to the bottom of the kettle. As the tomatoes cook, they will release more liquid. Cook on medium heat, stirring to ensure even cooking.
- Cook Until Soft: Cook the tomatoes until they are soft, about 10 minutes.
- Make the Tomato Juice: Use a food mill, Victorio Strainer, or a blender and strainer to turn the cooked tomatoes into juice.
- Canning the Tomato Juice: Follow safe canning practices to preserve your tomato juice. Add the correct amount of lemon juice (2 tablespoons per quart) to each jar.
What if You Forget the Lemon Juice?
Forgetting to add lemon juice happens. According to Food52, if you forget to add lemon juice, cook those tomatoes in a long-simmered sauce or braise. Doing so will ensure that any toxins that survived the water-bath process will be driven off. You can mark those jars for a long-cook time.
Additional Tips for Safe Tomato Canning
- Use Current, Research-Based Recipes: Always use current, research-based recipes when canning tomatoes or any other produce. Recommendations and preservation methods evolve, so using current methods is critical for a safely preserved product.
- Recommended Resources: Refer to trusted resources such as MSU Extension Michigan Fresh, the USDA Guide to Complete Home Canning, the National Center for Home Food Preservation, the So Easy to Preserve book, or a current Ball Blue Book.
By following these guidelines and understanding the importance of acidity, you can confidently can tomatoes at home, ensuring a safe and delicious supply of home-canned tomatoes to enjoy throughout the year.