Canning tomatoes is a fantastic way to preserve the summer’s bounty and enjoy garden-fresh flavor all year round. However, ensuring the safety of your canned tomatoes is paramount. A crucial step in the canning process is understanding how long to properly boil tomatoes, as this impacts both flavor and safety. Let’s delve into the details of boiling times for various canning methods, tomato preparations, and important safety considerations.
Understanding the Importance of Processing Time
Processing time, which includes boiling, is the duration for which jars of food are heated to a specific temperature to kill harmful microorganisms. Tomatoes, while acidic, often require added acidity to ensure their safety in canning due to variations in natural acidity levels. Insufficient processing can lead to spoilage or, more seriously, botulism poisoning, caused by the bacterium Clostridium botulinum. Botulism thrives in low-oxygen, low-acid environments like improperly canned goods.
The boiling time is influenced by several factors:
- The size of the jar used
- The density of the tomato product (whole, crushed, sauce)
- Whether the tomatoes are raw-packed or hot-packed
- Altitude
Ignoring these factors can compromise the safety of your canned tomatoes. It is crucial to follow established canning guidelines from reputable sources like the USDA or your local extension office.
Water Bath Canning vs. Pressure Canning: Which Method to Use?
There are two primary methods for home canning: water bath canning and pressure canning. The choice between these methods depends on the acidity of the food being canned.
Water bath canning is suitable for high-acid foods, meaning foods with a pH of 4.6 or lower. This includes most fruits, jams, jellies, pickles, and properly acidified tomatoes. In water bath canning, jars are fully submerged in boiling water for a specific period.
Pressure canning is necessary for low-acid foods, such as meats, poultry, seafood, and most vegetables. Pressure canning achieves higher temperatures than boiling water, which is essential for killing botulism spores in low-acid environments.
Since tomatoes are borderline in acidity, you might wonder which method is appropriate. Generally, tomatoes are canned using the water bath method, but with the addition of an acid (lemon juice, vinegar, or citric acid) to ensure safety. Always acidify your tomatoes when water bath canning. Pressure canning is also an option and is often recommended for larger batches or those seeking additional safety assurance.
Water Bath Canning Explained
Water bath canning involves immersing filled jars in a large pot of boiling water. The boiling water heats the contents of the jar, creating a vacuum seal as the jars cool. This process destroys spoilage organisms and prevents recontamination.
When using a water bath canner, make sure the jars are completely covered by at least 1-2 inches of water. Start timing the processing only when the water returns to a rolling boil after adding the jars.
Pressure Canning Explained
Pressure canning utilizes a specialized appliance that creates a pressurized environment. The increased pressure allows the water inside to reach higher temperatures than possible in a boiling water bath. This higher temperature is critical for safely canning low-acid foods.
Pressure canning requires careful adherence to manufacturer instructions and USDA guidelines. Specific pressure and processing times vary depending on the type of pressure canner (weighted gauge or dial gauge), the food being canned, and altitude.
Boiling Times for Water Bath Canning Tomatoes
The boiling times for water bath canning tomatoes vary based on several factors. Here is a general guideline, but always consult a current, reputable source like the USDA Complete Guide to Home Canning or your local extension office for the most accurate and up-to-date recommendations.
Important Note: These times are for adequately acidified tomatoes. Always add the appropriate amount of acid to each jar before filling with tomatoes.
Whole or Halved Tomatoes
-
Raw-Packed: This involves filling the jars with raw tomatoes and then covering them with hot tomato juice or water. This method may result in some shrinkage during processing.
- Pints: 85 minutes
- Quarts: 85 minutes
-
Hot-Packed: This involves pre-cooking the tomatoes before filling the jars. This helps to remove air and improves the vacuum seal.
- Pints: 85 minutes
- Quarts: 85 minutes
Crushed Tomatoes
-
Raw-Packed:
- Pints: 35 minutes
- Quarts: 45 minutes
-
Hot-Packed:
- Pints: 35 minutes
- Quarts: 40 minutes
Tomato Juice
- Hot-Packed:
- Pints: 35 minutes
- Quarts: 40 minutes
Tomato Sauce
- Hot-Packed: Tomato sauce requires a longer processing time due to its density.
- Pints: 35 minutes
- Quarts: 40 minutes
Boiling Times for Pressure Canning Tomatoes
Pressure canning tomatoes offers an alternative to water bath canning, particularly for those concerned about acidity levels. Always follow the manufacturer’s instructions for your specific pressure canner model.
Remember to properly vent the canner before pressurizing, and maintain the correct pressure throughout the processing time. After processing, allow the canner to cool naturally until the pressure returns to zero before opening.
Whole or Halved Tomatoes
- Pints: 25 minutes at 11 lbs pressure (weighted gauge) or 10 lbs pressure (dial gauge)
- Quarts: 25 minutes at 11 lbs pressure (weighted gauge) or 10 lbs pressure (dial gauge)
Crushed Tomatoes
- Pints: 15 minutes at 11 lbs pressure (weighted gauge) or 10 lbs pressure (dial gauge)
- Quarts: 20 minutes at 11 lbs pressure (weighted gauge) or 10 lbs pressure (dial gauge)
Tomato Juice
- Pints: 15 minutes at 11 lbs pressure (weighted gauge) or 10 lbs pressure (dial gauge)
- Quarts: 20 minutes at 11 lbs pressure (weighted gauge) or 10 lbs pressure (dial gauge)
Tomato Sauce
- Pints: 15 minutes at 11 lbs pressure (weighted gauge) or 10 lbs pressure (dial gauge)
- Quarts: 20 minutes at 11 lbs pressure (weighted gauge) or 10 lbs pressure (dial gauge)
Altitude Adjustments for Canning Times
Altitude plays a significant role in canning, as water boils at lower temperatures at higher elevations. This means you need to increase processing times to compensate for the lower boiling point. Failing to adjust for altitude can result in under-processing and unsafe canned goods.
For water bath canning:
- 1,001 – 3,000 feet: Increase processing time by 5 minutes
- 3,001 – 6,000 feet: Increase processing time by 10 minutes
- 6,001 – 8,000 feet: Increase processing time by 15 minutes
- 8,001 – 10,000 feet: Increase processing time by 20 minutes
For pressure canning, you may need to increase the pressure instead of the time. Consult the USDA guidelines or your local extension office for specific altitude adjustments for pressure canning.
Preparing Tomatoes for Canning: A Step-by-Step Guide
Before you even start boiling, proper preparation is essential for safe and high-quality canned tomatoes.
- Select high-quality tomatoes: Choose ripe, firm tomatoes free from blemishes or disease. Avoid using tomatoes from diseased plants.
- Wash and core tomatoes: Thoroughly wash the tomatoes under cool, running water. Remove the core using a paring knife.
- Peel the tomatoes: There are several methods for peeling tomatoes. One common method is to blanch them in boiling water for 30-60 seconds, then transfer them to an ice bath. The skins should slip off easily. Another method involves roasting the tomatoes to loosen their skins.
- Prepare the tomatoes according to your recipe: Depending on whether you’re making whole tomatoes, crushed tomatoes, juice, or sauce, you’ll need to chop, crush, or puree the tomatoes accordingly.
- Add acid: For water bath canning, add the appropriate amount of acid to each jar. This is crucial for ensuring the safety of your canned tomatoes. The recommended amount is typically 1 tablespoon of bottled lemon juice or ¼ teaspoon of citric acid per pint jar, or 2 tablespoons of bottled lemon juice or ½ teaspoon of citric acid per quart jar. You can also use 4 tablespoons of 5% acidity vinegar per quart, although this may affect the flavor.
- Pack the jars: Fill the jars with the prepared tomatoes, leaving the recommended headspace (usually ½ inch). Remove any air bubbles by gently tapping the jars or using a non-metallic spatula.
- Wipe the jar rims: Use a clean, damp cloth to wipe the jar rims to ensure a good seal.
- Place lids and rings: Place the lids on the jars and screw on the rings finger-tight. Do not overtighten the rings, as this can prevent the jars from sealing properly.
Essential Canning Safety Tips
- Use only approved canning jars and lids: Avoid reusing jars from commercially processed foods, as they may not seal properly.
- Follow tested recipes: Do not deviate from established canning recipes, as this can affect the safety of your canned goods.
- Ensure proper headspace: Headspace is the space between the top of the food and the lid. Too little headspace can cause the jars to overflow during processing, while too much headspace can prevent a proper seal.
- Process for the correct time: Follow the recommended processing times for your specific recipe, altitude, and canning method.
- Cool jars properly: After processing, remove the jars from the canner and let them cool undisturbed for 12-24 hours.
- Check for a proper seal: After cooling, check the jars for a proper seal. The lid should be concave and not flex when pressed.
- Label and store jars properly: Label the jars with the date and contents and store them in a cool, dark, and dry place.
- Inspect jars before use: Before opening a jar of canned tomatoes, inspect it for signs of spoilage, such as bulging lids, leakage, or unusual odors. If you suspect spoilage, discard the jar without tasting the contents.
Raw Pack vs Hot Pack: Impact on Boiling Time
The choice between raw packing and hot packing affects the processing time and the final product.
Raw packing involves placing uncooked tomatoes directly into the jars. The advantage of raw packing is that it’s faster, but the tomatoes tend to shrink during processing, leaving more headspace and potentially floating. The boiling time is usually longer for raw-packed tomatoes because they need more time to heat thoroughly.
Hot packing involves pre-cooking the tomatoes before filling the jars. This helps to remove air, reduces shrinkage, and improves the vacuum seal. The boiling time can be shorter for hot-packed tomatoes because they are already partially heated.
Troubleshooting Common Canning Problems
Even with careful preparation, canning problems can arise. Here are some common issues and how to address them:
- Jars not sealing: This can be caused by improper headspace, damaged jar rims, or not tightening the rings properly.
- Siphoning (liquid loss): This can occur if the pressure fluctuates during processing or if the jars are cooled too quickly.
- Cloudy liquid: This can be caused by hard water or starch in the tomatoes.
- Food discoloration: This can be caused by over-processing or using old spices.
In conclusion
Canning tomatoes is a rewarding experience that allows you to enjoy the flavors of summer all year round. By understanding the importance of processing time, choosing the right canning method, adjusting for altitude, and following safe canning practices, you can ensure that your canned tomatoes are both delicious and safe to eat. Always consult reputable sources like the USDA Complete Guide to Home Canning for the most up-to-date information.
Why is boiling tomatoes before canning necessary?
Boiling tomatoes before canning is crucial for several reasons, primarily related to food safety and the quality of the final canned product. The high heat helps to eliminate bacteria, yeasts, and molds that can spoil the tomatoes and potentially cause serious illness, such as botulism. Properly boiled tomatoes also ensure a good vacuum seal during the canning process, which is essential for long-term storage.
In addition to safety, boiling tomatoes also softens the tomato flesh, making them easier to process and pack into jars. This helps to remove air pockets, further contributing to a stronger vacuum seal. Furthermore, heating the tomatoes releases their natural juices, which helps to create a consistent and flavorful liquid environment within the jar. This ensures even heat penetration during processing and improves the overall texture and taste of the canned tomatoes.
How long should I boil tomatoes before canning?
The ideal boiling time for tomatoes before canning depends largely on how you’re preparing them and the specific recipe you’re using. Generally, if you are simply blanching tomatoes to remove their skins, a brief dip in boiling water for 30-60 seconds is sufficient. For recipes like tomato sauce or salsa where the tomatoes will be further cooked during the canning process, boiling them for a longer period, such as 10-15 minutes, is recommended to soften them and release their juices.
It’s important to consult a tested and approved canning recipe for precise boiling times. These recipes are carefully developed to ensure adequate heat penetration and acidity levels for safe canning. Always follow the recipe’s instructions regarding boiling time, jar size, and processing method (water bath or pressure canning) to prevent spoilage and ensure the safety of your canned tomatoes.
Can I skip boiling tomatoes and can them raw?
While it is technically possible to can raw-packed tomatoes, it’s generally not recommended for safety reasons, especially for whole or halved tomatoes. Raw-packed tomatoes require longer processing times to achieve the same level of heat penetration as pre-cooked tomatoes. This extended processing can result in a softer, less flavorful product, and increases the risk of spoilage due to uneven heating.
More importantly, raw-packed tomatoes may not reach a high enough temperature to eliminate botulism spores, a serious foodborne illness risk. Cooking the tomatoes beforehand reduces their volume and helps to drive out air, allowing for better heat penetration during processing. Always prioritize safety by following tested canning recipes that involve some level of pre-cooking or boiling the tomatoes.
What’s the difference between water bath canning and pressure canning when processing tomatoes?
Water bath canning is suitable for high-acid foods like jams, jellies, and certain tomato products that have been acidified with lemon juice or vinegar. This method involves immersing filled jars in boiling water for a specified amount of time, allowing the heat to kill spoilage organisms. The high acidity of the food helps to inhibit the growth of botulism spores.
Pressure canning, on the other hand, is necessary for low-acid foods like vegetables, meats, and some tomato products that haven’t been sufficiently acidified. A pressure canner creates a superheated environment that reaches higher temperatures than boiling water, effectively killing botulism spores and other harmful bacteria. Since tomatoes are borderline in terms of acidity, adding lemon juice or vinegar is often recommended, especially when using water bath canning, to ensure safety.
How do I peel tomatoes easily after boiling?
The blanching process of briefly boiling tomatoes before canning makes peeling them incredibly easy. Simply score an “X” on the bottom of each tomato before dropping them into boiling water for 30-60 seconds. This scoring allows the skin to contract and loosen during the boiling process.
After blanching, immediately transfer the tomatoes to a bowl of ice water to stop the cooking process. This rapid cooling will further loosen the skin. You should then be able to easily peel the skin off with your fingers, starting at the scored “X” mark. The skins will slip right off, leaving you with perfectly peeled tomatoes for canning.
What if my canned tomatoes don’t seal properly?
If your canned tomatoes don’t seal properly after processing, it’s important to address the issue immediately to prevent spoilage. If the jars have cooled within 12-24 hours and haven’t sealed, you have a couple of options. You can reprocess the tomatoes using new lids and following the original processing time.
Alternatively, you can store the unsealed jars in the refrigerator and use the tomatoes within a few days. It’s crucial not to consume unsealed canned goods that have been stored at room temperature for longer than a couple of hours, as they may be contaminated with harmful bacteria. To ensure proper sealing in future canning sessions, always inspect the jar rims for chips or cracks, use new lids each time, and follow the recommended headspace and processing times in your chosen recipe.
Can I use frozen tomatoes for canning, and does that affect the boiling time?
Yes, you can use frozen tomatoes for canning, and in many cases, it’s a convenient way to preserve your harvest. Thawing frozen tomatoes is not necessary before using them in canning recipes. In fact, adding them frozen can sometimes help to retain more of their texture and flavor.
Using frozen tomatoes may slightly affect the boiling time, as the tomatoes will release more water as they thaw during the heating process. Follow a tested canning recipe and adjust the cooking time as needed to achieve the desired consistency for your tomato product. Ensure that the tomato mixture reaches a rolling boil before filling the jars for canning, and always follow the recommended processing time for the specific canning method you are using.