Tomatoes are the most popular food for canning at home. They are versatile, abundant, and easy to can. There is no doubt that tomato canning season is here as the number of “tomato canning” questions rise—floating, separation, loss of liquid, air bubbles. Do any of these problems affect the safety? AnswerLine is here to answer these questions.
Float
Floating tomatoes (tomatoes or tomato pieces at the top of the jar, liquid at the bottom) may be a visual disappointment but does not affect the safety of the product. Floating is more likely to happen with whole or quartered tomatoes and with a raw pack. The floating is caused by the natural air and water in the tomatoes which releases during processing. Raw food has a lot of air in it. The volume of food put in a jar before processing might actually only be ¾ food and ¼ air trapped inside the food. During processing, this air will escape from the food and rise to the top of the jar. Float can be minimized by choosing fresh, firm tomatoes, reducing the amount of liquid in the jar (replacing with product), packing the jar as firmly as possible without crushing the tomatoes, removing air bubbles, and using a regular mouth jar. Sometimes turning the jars upside down after they have cooled for 24 hours and letting them rest for a period of time will bring the liquid and solids back together. Canning crushed tomatoes and/or using a hot pack often eliminates the problem.
Separation
Sometimes crushed or puréed (juice) tomatoes will separate in the jar into tomato solids and liquid. Separation is another visually disappointing issue that does not affect safety. When tomatoes are cut or crushed before heating, exposure to the air activates a natural enzyme, Pectose (Pectinesterarse), found in high concentrations in tomatoes. The enzyme is activated when tomatoes are cut. This enzyme breaks down pectin which causes the liquids and solids to separate. Heating tomatoes immediately after they are cut or crushed to 180F (82C) inactivates this enzyme. This is the reason that many tested recipes direct one to cut small quantities of tomatoes and heat them in batches. Gently shaking the jars after the product has cooled for 24 hrs may bring the solids and liquid back together.
Loss of Liquid
Loss of liquid does not cause food to spoil, though the food above the liquid may darken. If, however, the loss is excessive (for example, if at least half of the liquid is lost), refrigerate the jar(s) and use within 2 to 3 days1. Jars with milder liquid loss should be used sooner rather than later so place them at the front of the shelf so they get used first. Penn State Extension advises on the three likely causes of liquid loss or siphoning from the jar during processing of tomatoes or other fruits and vegetables—raw pack, rapid fluctuation of temperature in the canner, and removing the jars too quickly after processing. In addition to the causes noted, improper headspace and loose bands are other sources of liquid loss. Food expands during processing and if a jar is overfilled there is insufficient room for the expansion. When this happens, water will push out to make room for expansion. If canning ring bands are too loose, liquid will escape and may also cause seal failure. And like floating and separation, removing air bubbles from the jar prior to lidding helps to lessen liquid loss.
Air Bubbles
Removing of air, also known as de-bubbling, prior to processing is an important step in canning. Air trapped in jars can interfere with the jar’s ability to drive out the extra air in the top causing too much headspace, floating, loss of liquid, and a poor or no seal. Additionally, too much air space results in canned product above the canning liquid which can lead to discoloration and the development of off-flavors. A bubble remover and headspace tool is designed for air removal; a plastic or silicone knife or spatula handle will do the same as long as the tool used is heat resistant to handle the heat of a hot pack. Do not use anything metal to remove air as it may cause hairline cracks in the jar. Simply run a bubble popper around the edges of the jar, gently shifting the food, so that trapped air is released as much as possible. After the air bubbles have been removed, more liquid may need to be added to the jar to ensure proper head space.
After processing, tiny air bubbles may be noticed in the product. If these bubbles are inactive, they are benign or harmless. If the bubbles are actively moving or fizzing up to the top of the jar when opened, the product may be fermenting or contaminated. Products with active air bubbles should not be used and properly discarded.
Despite one’s very best efforts to diminish floating, separation, loss of liquid, or air bubbles, it seems that there is one more non-scientific reason—the phase of the moon! Or that it just happens! As long as a tested recipe has been used and carefully followed, the jar seals securely, and there is at least half of the liquid in the jar, the tomatoes are safe inside the jar.
Source:
1FAQs. “Should liquid lost during processing be replaced?” National Center for Home Food Preservaton.
Thank you for so many helpful answers! I water bath can jellies and salsas, always from tested recipes, and adjusted for altitude. I live at 10,600 ft, so I usually process half pints or pints and add 5ish minutes to instructions for 8-10,000 ft. 2 questions: 1) have you seen any tested recommendations for elevations above 10,000 ft? 2) I am thinking about moving into canning tomatoes and am trying to decide if I should get a pressure canner if I do. What are the differences in the final product (taste, texture, etc) if you do tomatoes in a water bath vs. pressure canning? Thank you!
Maggie, great questions!!! And kudos for practicing home canning safely. If you move to a high elevation, check recipes and guidelines provided by Colorado State University (Food Smart Colorado), Utah State University, and New Mexico State University. It would also behoove you to check with the extension office in the county that you may potentially reside for recommendations. As for differences in the final product between water bath and pressure canned–not really all that much. Recipes are tested for optimal quality while still rendering a safe product. Thank you for reaching out to AnswerLine.
Thanks for the helpful information!
One of the jars of halved tomatoes I canned a few days ago appears to have fermented. It pushed through the seal, and the product was about 1/4” above the mouth of the jar. The tomatoes had an unpleasant, fermented smell and I could see the fizzy bubbles in the jar. I destroyed the product but am left wondering how and why this jar became contaminated. I’m vigilantly and anxiously watching the other jars! Thanks for any information and advice.
Hi Amanda, I need to know how you processed your tomatoes to more fully answer your question. If you carefully followed a tested recipe, added bottled lemon juice to acidify, and processed the tomatoes for the correct amount of time for your altitude, this should not be happening. It is important to follow a tested recipe to eliminate bacterial growth through the correct processing time with peeling or acidifying. If the jar that is fermenting was processed with the jars that you are watching, I suspect that they may be trouble, too. Check out the National Center for Home Food Preservation for safe ways to can halved tomatoes.
Hi! I canned some chili sauce last night with my garden tomatoes. It became very late (2am) and even though I probably should have cooked longer to make thicker, I stopped and processed. Would I be able to open the jars back up and put back over heat to cook down further?
HI Sara, if you desire a thicker sauce, you may open and cook the sauce longer followed by reprocessing. However, when ready to use, you could cook it down at that time and save the reprocessing.
I forgot to remove the bubbles and, although my jars are sealed, they have about an inch of headspace. I did add the required lemon juice.
Also, I don’t think they were all visibly boiling inside the jar when they were removed from the water bath canner after 45 minutes.
Are these safe to store on a shelf? Eat now?
Someone told me to put the jars in the refrigerator and boil the tomatoes for 15 minutes before using them; is that necessary? Or should I throw them away and consider it a lesson learned?
Diane, If you used lemon juice, processed the tomatoes correctly (time and/or pressure if pressure canned) using USDA guidelines, and the jars sealed, the tomatoes are safe for shelf storage despite the fact the the headspace is 1″. Liquid loss can also happen due to siphoning. Use the tomatoes are you would normally. Thank you for reaching out to AnswerLine.
I’m looking for a recipe fir a meatless spaghetti sauce… do you have one?
Hi Jan, the recipe we would recommend comes from the National Center for Home Food Preservation, a safe site for canning and preserving. The recipe link is https://nchfp.uga.edu/how/can_03/spaghetti_sauce.html
Hello Marlene,
Thank you for this very useful information! I just canned some tomato puree and processed them in boiling water for 45 minutes. They are sealed. Most of them are fine, but some of the jars that contain more liquid have small, white bubbles that move when I tilt the jar. They are not active on their own but show up when I tilt the jars from side to side. they are very active when I move the jars.
I would appreciate any information you have on this.
Thank you very much for your time!
Hi Antonella, (love your name)
It sounds like the bubbles you are seeing are merely air bubbles which didn’t get removed before processing. As long as they are not active like you would see in a carbonated drink, the tomatoes are safe. However, be sure that your processing time is correct for your location. 45 minutes is correct for altitudes of 1000 ft or less.
Hi Marlene,
Thank you so much. You have no idea how relieved I am to hear this! The bubbles are definitely not active when the jar is resting, only when I move the sauce around. I was worried because the bubbles are white and bubbly, unlike the usual air pockets that will sometimes form in the sauce. Will the bubbles eventually find their way out?
Thank you again!
Antonella
Hello again,
I wish to share one more comment. Thank you for your time! Although they do not move when undisturbed, the bubbles are white, tiny, all clustered together and almost foamy. It is the foamy part that concerns me. Is there a reason for this appearance?
Again, thank you kindly for your time.
Antonella
Hi Antonella, without seeing your bubbles, it is hard to tell; we know that moving bubbles are a definite problem. I am unsure about the foamy bubbles. Take a look at the picture at this website: https://sanctuarygardener.wordpress.com/2014/07/11/tomato-canning-failure/ While this is not a research based website, it may help identify the bubble characteristics you describe. If your bubbles look something like this, then perhaps there is concern. I would suggest opening a jar and see if the bubbles move to the top. If they move like a carbonated beverage, there is definitely something wrong with the jars exhibiting this phenomenon. Whenever there are concerns/doubts about something that has been home canned, it is best to throw it out.
I use a pressure canner to process my tomato harvest. I fill pint and quart jars with roasted, pureed tomatoes leaving about a 1/2 inch at the top before sealing. I notice that after I cool and shelve the jars that an air gap appears at the top, sometimes as much as an inch or more and I wonder if the jars are still safe to store and eat.
I gather the sauce has just settled with time and perhaps some of the liquid separated out, but I am concerned about that air gap.
Are they safe or should I open the jars and store the contents some other way?
Many thanks.
Hi Sheila, it seems you have loss some liquid during processing. If you used a tested recipe, acidified the tomatoes, and processed them correctly (time and pressure for altitude), the loss of some liquid does not make them unsafe. Jars with more than 1/2 inch of headspace should be used first. If the loss of liquid is severe, those jars should be refrigerated and used within 2-3 days.
Hello Marlene, thank you so much for taking the time to research my air bubble issue further. The link you sent me was very helpful in identifying the foamy white bubbles in my tomatoes. The picture of the bubbles on the website is exactly what is happening with mine. I lost half of my tomatoes to these white foamy bubbles. The other half of my tomatoes seem just fine. Thank you again for your time and assistance with my canning issue!
I forgot to water bath my tomato sauce after filling the jars. I made it 13 days ago. Can I water bath them now or is the entire batch a loss?
Hi Christina, reprocessing can only be done in the first 24 hours. I am sorry to say that your tomato sauce should not be used as it is not safe. Please discard it. Oregon State has a wonderful canning app that reminds you of the steps necessary to prepare a safe product. It is usable on both android and IOS systems. https://catalog.extension.oregonstate.edu/pnw689
Hello Marlene. Thank you for your helpful information. I have some questions I can’t seem to find answers for anywhere.
1. If I’m supposed to can at 10 lbs pressure but only have a 15 lbs weight, can I use the 15 lbs weight at the 10 lbs time?
2. Can I can over ripe tomatoes? I would pressure can these.
3. I’ve read that you should not use your own sauce and salsa recipes but are my recipes safe if I pressure can them based on the longest time required for any included ingredients?
Thank you in advance!
Hi Geneva,
Great questions –
1) Yes, the only disadvantage of added weight is over processing so product may be softer; over processing is always better than under processing.
2) Using overripe tomatoes in home canning is discouraged due to concerns related to acidity, spoilage risks, and the overall quality of the canned product. Pressure canning does not change any of the risks. The best preservation method for these tomatoes is to freeze them. Source: https://extension.umn.edu/preserving-and-preparing/canning-tomato-products-safety-guidelines
3) Salsas are a combination of acid and high-acid ingredients. PH is an important factor in salsas regardless of how it is processed; presently there are no tested recipes for pressure canning salsa. Check out “It’s Salsa Time” (https://blogs.extension.iastate.edu/answerline/2023/08/22/its-salsa-time/) for more information on salsas, the need to use a tested recipe, allowed substitutions, and what to avoid.
Hi again Marlene. Thank you for your help. Has pressure canning salsas been shown to be unsafe or is it that it’s simply never been tested? I’m just needing some clarification.
Geneva
I froze tomatoes this year (very busy at harvest) with intention of canning later…now beginning November. I plan to can this week. After canning, when is earliest that I can use the canned tomatoes? I can’t find anything about any length of time (if any) that a canned product (canned per safe recipe) one should wait before opening for use.
Thank you!
Hi Nancy, there are no rules/recommendations about when to open and use a safely canned product with the exception of some pickles which need time to absorb flavors and jams and jellies which continue to set after processing. If extended time is needed, the recipe usually indicates such. Happy Canning!
@Nancy Brown
As already said canned products can be used immediately or anytime forward. With tomato sauces especially where herbs spices have been added the flavor can need sometime to fully develop. I find a month is plenty. But in terms of safety as has already been said there is no min time period.A maximum period is more about nutriention and flavor quality than safety.
I just opened a three jars of halved, skinless tomatoes canned in September, and in each, the tomatoes floated to the top and are somewhat dry. They all smell fresh and divine. Jar 1 has a spotless lid. Jar 2 has streaks of dried tomato and seeds across the top, and Jar 3 has similar streaks in addition to a few black spots. Which jars are the keepers?
HI Chris, thank you for reaching out to AnswerLine. If you canned the tomatoes using a tested recipe (National Center for Home Food Preservation, USDA, or extension publication) and followed the directions completely, all three jars should be safe. If done otherwise, I cannot say the same. It is not uncommon for tomatoes to float (particularly if a raw pack was used) and when they come above the juice, they will appear dry. The floating is caused by the natural water and air in the tomatoes which gets released in processing and as they cool. Float can be minimized by choosing fresh, firm tomatoes, reducing the amount of liquid in the jar or packing the jar as firmly as possible without crushing the tomatoes, and removing air bubbles. Canning crushed tomatoes and/or using a hot pack often eliminates the problem
I canned some tomatoes using the recipe in the “Ball Book of Canning and Preserving”. They were raw packed into the jars pressing down until the tomatoes and their natural juice came to within a half inch from the top. After they cooled the tomatoes and their juice dropped from an inch to an inch and a half below the top. Are these tomatoes safe to eat or should I discard them?
Hi David, Thanks for reaching out to AnswerLine. It is not uncommon for there to be some liquid loss with raw pack tomatoes. If you followed the recipe precisely and processed the tomatoes correctly, the tomatoes are safe to eat. I would advise that you use them sooner rather than later. The tomatoes at the top of the jars may darken over time; this does not make then unsafe.