Tomato home canning considerations: colour, variety, ripeness

When you are home canning with tomatoes, does the colour of the tomato matter? Can you use cherry tomatoes? Can heritage tomatoes that ripen to green be used in recipes that call for green (unripe) tomatoes? What about the less-juicy ‘paste’ tomatoes? And how much salt do you need to add to make a tomato product you canned safe.

This is an ‘advanced’ page, examining such questions.

Follow this link if you are just after actual tomato recipes right now.

Background: acidity levels in the tomato family

From lowest to highest

1. Ripe tomatoes of any colour (red, orange, yellow, purple, ripe green, etc);
2. Unripe green tomatoes;
3. Tomatillos

Tomatillos are close cousins to tomatoes.

The colour of ripened tomatoes doesn’t matter safety-wise

Ripe tomatoes are interchangeable in canning recipes in terms of safety, regardless of the colour.

Ripe tomatoes of whatever colour  are deemed equivalent in terms of acidity and are interchangeable in home canning in terms of safety: be they red, yellow, purple, orange, black, brown, striped, or varieties which ripen naturally to green (such as German Green or Zebra Striped).

Part of that being “deemed equivalent” is that they are all deemed to require the USDA’s acidification process, which will push them all into the safe, high acidity range for home canning.

Here’s what various experts in the field say on the matter of differently-coloured tomatoes being interchangeable in canning recipes.

Carol Ann Burtness at the University of Minnesota Extension Service says,

Tomato varieties and colors can mixed and matched for salsa but still need added acid to make sure the product will be safe.” ^[1]Burtness, Carol Ann. Canning Tomato-Based Salsa Safely. University of Minnesota Extension Service. 2014. Accessed June 2016 at https://www.extension.umn.edu/food/food-safety/preserving/tomatoes-salsa/canning-tomato-based-salsa-safely  

Penn State Extension says,

Canning Pink, Yellow, or Orange Tomatoes.

Q: Are yellow tomatoes, pink, or orange tomatoes canned the same way as red tomatoes?

A:  All tomatoes, no matter what the color, are canned by the same method as red tomatoes. Be sure to add the correct amount of lemon juice or citric acid as described at the website below. ^[2]Penn State Extension. Food Preservation Q & A. Canning Pink, Yellow, or Orange Tomatoes. Accessed June 2016 .

Penn State also says that if yellow tomatoes seem to taste less tart / acidic than other tomatoes, it doesn’t mean that they are actually: it’s because they have more sugars in them that mask the tartness (the same way sugar masks the tartness of rhubarb):

Other misconceptions are that yellow tomatoes are lower in acid than red tomatoes ….. Yellow tomatoes taste less acid because they contain more natural sugars.” ^[3] Penn State Extension. Acidify Tomatoes before Canning. 10 August 2012. Accessed June 2016.

Barb Ingham at the University of Wisconsin Extension concurs,

Even small-fruited cultivars and white, yellow and pink tomatoes are in the same acidity range as most standard red tomatoes. The difference in taste of these tomatoes — falsely called ‘‘low acid’’ in some seed catalogs — is due to their higher sugar content that masks tartness….Because of the potential variation in acidity, treat all tomatoes the same — whether they be yellow, red or pink.” ^[4] Ingham, Barb. Tomatoes Tart & Tasty. University of Wisconsin Extension. (B2605). R-5-2008.  2008. Page 2.

Julie Garden-Robinson says the same about the background acidity and tartness of yellow tomatoes being masked by the natural sugars in them,

Often the question comes up about good yellow-fruited slicing tomatoes, their quality, acidity and productivity. One of the best on the market is ‘Lemon Boy.’ It bears clear lemon-yellow fruit, inside and out, and has a sweet, mild flavor. The fruit matures in about 72 days and averages 7 ounces. This is an indeterminate variety so it would need staking and some pruning. It is commonly believed that yellow tomatoes are low-acid, but tests have shown that their acidity levels are about the same as red tomatoes — pH 4.6 — which is the dividing line between high- and low-acid foods.” ^[5]Garden-Robinson, Julie. From the Garden to the Table: Salsa! North Dakota State University Extension. Revised 2015. FN584. Accessed June 2016. 

Karma Metzgar at the University of Missouri Extension says,

How do you can yellow tomatoes? Yellow tomatoes are canned by the same method as red tomatoes. This holds true for pink, orange, and other rainbow colors of ripe tomatoes, so you can mix and match as you preserve salsa or canned tomato products.” ^[6]Metzgar, Karma. “Can I Can Yellow Tomatoes?” and Other Tomato Questions. University of Missouri Extension. 5 May 2009. Accessed June 2016. 

Elizabeth Andress, head of the National Center for Home Food Preservation, says,

It is ….. currently accepted that orange or yellow tomatoes, based on limited testing of varieties being grown at this time, can be safely canned with these directions.”  ^[7] Andress, Elizabeth L. and Judy A. Harrison. Preserving Food: Canning Tomatoes and Tomato Products.  University of Georgia Cooperative Extension. FDNS-E-43-2 . Revised May 2015. Accessed June 2016.  

Lisa Barlage of Ohio State University Extension says,

Treat all ripe tomatoes (yellow, green, pink, orange, red, etc.) the same.” ^[8] Barlage, Lisa. Canning Tomato Products. Ohio State University Extension. Family and Consumer Sciences. HYG-5337. 28 May 2015. Accessed June 2016.

Even though all ripe tomatoes are interchangeable in terms of safety, as seen above, swapping them can change the flavour:

Green tomatoes, yellow tomatoes, orange tomatoes and tomatillos can be used in place of red tomatoes safely. These types of tomatoes may change the flavor.” ^[9] Balkeslee, Karen. Sensational Salsa. Kansas State University Research and Extension. April 2007.

Swapping them can also change the colour of the end product. This can be interesting in concoctions which are deliberating aiming for a different colour to delight the eyes of jaded palates — such as in salsas which are designed to be yellow.

Some people point out that a colour change may not always be desirable, though. A Washington Post writer feels that the tomato sauce made from yellow tomatoes would not be visually appealing:

Consider the color of the tomato when making these long-cooked products [Ed: tomato sauces boiled down before canning.] Yellow tomatoes or green (ripe) tomatoes do not cook down to an attractive color; try the dark ruby, carmine or purplish types for a gorgeous end product.” ^[10] Barrow, Cathy. Tomato canning q&a. Washington, DC: Washington Post. 14 August 2012. Accessed June 2016.  

The colour of a cooked tomato sauce made from yellow tomatoes, though, might be a personal preference.  The writer of a blog post for Fillmore Containers liked the colour of tomato sauce made with yellow tomatoes….

….not one of our batches turned out exactly like the previous. Some had more reds, and then the next one might have more of the yellow tomatoes – which resulted in a lovely warm sauce much lighter in color.” ^[11]Fillmore Containers Blog Posting, 12 September 2013. Accessed June 2016 at https://blog.fillmorecontainer.com/index.php/2013/09/12/roasted-tomato-sauce-for-freezing-or-canning/.  

Note that a recipe calling for yellow tomatoes may be counting on a bit of their sweetness, so if you use another colour of tomato instead, you may want to add a bit (or a bit extra) sweetener to the recipe.

Recipes for yellow tomatoes

Sweet Yellow Tomato Chutney. Ball. (link valid as of June 2016)

Yellow Tomato and Mango Salsa. (Canadian Living Test Kitchen: The Complete Book of Preserving. 2012. Page 206.)

Paste type tomatoes

When you are making tomato sauces, or tomato pastes, it can be better energy wise to start from the category of tomatoes called “paste tomatoes.” That’s cultivars such as Amish Paste, Roma, San Marzano, Torpedo, Torino, etc.

The reason is that those tomatoes are less watery (i.e. juicy) to start with, so far less boiling time (and therefore far less cooking fuel) is needed to drive off water to thicken the mixture down into a sauce. This can both save you money and reduce your carbon footprint. That being said, if someone hands you a few free bushels of tomatoes, you can’t look a gift horse in the mouth.)

The Ball / Bernardin Complete book says,

Both globe (round) and oblong (plum or paste) tomatoes are suitable for home canning. Although round tomatoes are noted for their juicy eating quality, they require extra cooking to reach the thicker consistencies home canners expect. Because plum tomatoes are meatier and less juicy, they create thicker sauces in less cooking time. Plum tomatoes contain elevated levels of sugar, acid and pectin, which also makes them preferable for home canning.” ^[12]Kingry, Judi and Lauren Devine. Ball / Bernardin Complete Book of Home Preserving. Toronto: Robert Rose. 2015. Page 352.

Cathy Barrow, writing for the New York Times, says

The more watery the tomato, the longer the cooking time.” ^[13] Barrow, Cathy. Tomato canning q&a. Washington, DC: Washington Post. 14 August 2012.

If you experience a lot of separation of water and solids with your crushed tomatoes, using less watery tomatoes (that is, paste tomatoes) can help.

Paste type tomatoes can also help you produce thicker, less runny salsas.

Carol Ann Burtness at the University of Minnesota Extension Service says,

Italian plum-style or paste tomatoes will produce thicker salsas than slicing tomatoes.” ^[14]Burtness, Carol Ann. Canning Tomato-Based Salsa Safely.

As a minor aside, paste type tomatoes are less acidic than standard, juicier “slicing tomatoes”:

Paste tomatoes consistently are lower in acid — higher in pH — than standard tomatoes.” ^[15] Ingham, Barb. Tomatoes Tart & Tasty. University of Wisconsin Extension. (B2605). R-5-2008.  2008. Page 2.

Note that this is in conflict with what Ball / Bernardin said above about acidity: “Plum tomatoes contain elevated levels of …acid…” ^[16]Kingry, Judi and Lauren Devine. Ball / Bernardin Complete Book of Home Preserving. Toronto: Robert Rose. 2015. Page 352.

Regardless, the USDA’s acidification formula renders all types of ripe tomatoes equally safe for home canning in whatever tested recipe you are using.

Green unripe tomatoes

When a home canning recipe calls for green tomatoes, it means unripe tomatoes. It does not mean a heritage variety of tomato such as German Green which ripens to green. It means a tomato that is still green because it is unripe, and thus has a higher acidity range than ripe tomatoes. A recipe calling for green tomatoes will be looking for that acidity range for safety.

In terms of safety, you can swap out ripe tomatoes and swap in unripe green tomatoes in recipes. That’s because green tomatoes are more acidic, so if anything they will increase the safety level of a recipe (though of course a tested recipe doesn’t need that to happen.)

You can’t go the other way, though, swapping out green unripe tomatoes and swapping in ripe tomatoes — because you would be reducing the overall acidity (and thus safety levels) of the product.

So when a recipe calls for green tomatoes, use green, unripe tomatoes, and not ripe tomatoes. The only safe substitution that may be made for green tomatoes is swapping in tomatillos, as they also are very acidic, if not moreso. The USDA’s table of “Approximate pH of Foods and Food Products” assigns a pH value of 3.83 to tomatillos. ^[17] USDA. Center for Food Safety and Applied Nutrition. Acidified and Low-Acid Canned Foods. April 2007. Accessed March 2015. So you can’t downgrade to ripe tomatoes, but you can upgrade to tomatillos.

The University of Kentucky Extension Service notes though that using green, unripe tomatoes in a recipe for regular, ripe tomatoes — while completely safe — may change the flavour of your product:

Green tomatoes may be used in place of ripe tomatoes, but the flavour will be different.”  ^[18]Bastin, Sandra and Debbie Clouthier. Home Canning Salsa. University of Kentucky Extension Service. FCS3-581. Feb 2014. Page 1. Accessed June 2016. 

Spaghetti sauce made with green, unripe tomatoes might be a hard sell to a crowd of kids for an after-school supper.

Even though green tomatoes are more acidic than ripe tomatoes, if you were to can them on their own, say, as crushed tomatoes, the USDA still requires that you apply the regular tomato acidification process to them:

Green tomatoes can be canned safely with any of the following recommendations.” ^[19] Andress, Elizabeth L. and Judy A. Harrison. Preserving Food: Canning Tomatoes and Tomato Products.  University of Georgia Cooperative Extension. FDNS-E-43-2 . Revised May 2015. Accessed June 2016. 

Part of the reason for this may be that the pH on unripe tomatoes can vary wildly based on what particular stage of “unripe” an unripe tomato is at:

The acid content is lower in immature fruit and is highest at the stage when color starts to appear, with a rapid  decrease when the fruit ripens…. maximum acidity is at the pink stage of tomato fruits with subsequent fall.”  ^[20] K.M. Moneruzzaman, A.B.M.S. Hossain, W. Sani and M. Saifuddin. Effect of Stages of Maturity and Ripening Conditions on the Biochemical  Characteristics of Tomato. American Journal of Biochemistry and Biotechnology 4 (4): 336-344, 2008. Page 336.

All that being said, added acidity or not, the Ball / Bernardin Complete book isn’t crazy about you make a pure tomato product — such as tomato sauce — out of green tomatoes:

While green (unripe) tomatoes can be safely used as an ingredient in many home canning recipes, we don’t recommend preserving them as a stand-alone item. Green tomatoes contain a compound called solanine, which can be toxic if consumed in large amounts. Moreover, solanine — like other alkaloids, such as caffeine — contributes an astringent taste to foods that must be balance by sweet fruits, vegetables or sugar. The darker the green, the higher the tomato’s solanine content. The safest strategy is to use only pale green tomatoes or those tinged with red. If you have a supply of green tomatoes, you can ripen them considerably by placing them in a brown paper bag or between layers of newspaper until the intense green pales.” ^[21]Kingry, Judi and Lauren Devine. Ball / Bernardin Complete Book of Home Preserving. Toronto: Robert Rose. 2015. Page 352.

[Ed: Note that the Bernardin voice is often one of the more conservative voices in the home canning crowd, requiring acidification of apple sauce even, long before Ball did, and still wanting canning lids to be pre-simmered in 2016.]

Interestingly, you are allowed to use green tomatoes instead of tomatillos in approved salsa recipes, according to the University of Wisconsin extension service:

You may safely substitute green tomatoes for tomatillos in an approved salsa recipe (try Green Tomato Salsa!), and you may also safely substitute green tomatoes or tomatillos for ripe tomatoes in any approved salsa recipe.” ^[22]Ingham, Barb. What to do with green tomatoes? University of Wisconsin Extension. Blog entry 19 September 2013.

It’s important to note of course that good quality canning recipes aren’t just all about safety — they are also about good tasting products that people want to eat, or they’d be safe all right: no one would eat them in the first place.

So, bear in mind that recipes calling for green tomatoes do so not just for safety, but often because their tart, sour taste, and / or their drier, coarser, firmer texture when chopped plays an important role in the taste and consistency of the end product.

Green tomato canning recipes

Here’s the link for green tomato canning recipes that Healthy Canning has tried from reputable sources.

Cherry or grape tomatoes

The question of home canning cherry (and grape) tomato is not addressed broadly by many of the reputable sources out there. Given that we are directed to peel tomatoes before canning to reduce bacterial load going into the canner, one immediate challenge comes to mind when thinking of these tomatoes and their size, that there wouldn’t be much left another peeling them, never mind that it would take days to do so.

Besides the “peeling for safety” factor, because cherry tomatoes are just so much skin relative to flesh, there might just be way too much tough, stringy skin in an unpeeled cherry tomato mixture even for those who say they can normally overlook tomato skin.

Here’s what Angela Fraser of North Carolina State University says on the topic:

Can cherry tomatoes be canned like other tomatoes? Cherry tomatoes may be canned just like any other tomatoes. Since peeling them may be a tedious task, using them for juice may be the best use for them. If they are canned unpeeled, the peeling will probably separate during canning and give a less than desirable product.” ^[23] Angela M. Fraser, Ph.D., Associate Professor/Food Safety Specialist, and Carolyn J. Lackey, Ph.D., R.D., L.D.N., Professor/Food and Nutrition Specialist, North Carolina State University (August 2004). Can cherry tomatoes be canned like other tomatoes? Accessed June 2016 at http://www.foodsafetysite.com/consumers/faq/?m_knowledgebase_article=424

Utah Extension suggests considering cherry tomatoes for drying:

Small cherry tomatoes or tomatoes with a high solid content, such as Romas, work best for drying. Dried tomatoes are good in soups, stews, sauces, and salads ” ^[24] Williams, Pauline and Charlotte Brennand. Preserve the harvest: Tomatoes. UtahState University Cooperative Extension. Reviewed March 2010. Page 8.

If you have a food mill to make the work easy for you, cherry tomatoes can be used for home-canned tomato juice.

Home canning recipes for cherry or grape tomatoes

As of 2016, we are aware of two tested recipes for pickled cherry tomatoes, and have them both.

Tomatillos

See dedicated page on home canning tomatillos.

The role of salt in home canning tomatoes

The safety of home canned tomato products depends completely on either:

• (A) acidification, for products that are water-bathed (or steam canned), which prevents botulism spores from “blooming” PLUS normal heat temperature to kill off salmonella, listeria, mould spores, etc, which don’t mind acidity, or
• (B) extreme heat, for products that are pressure canned, which actually kills botulism spores off, plus all the other nasties as well.

Salt plays 0 — zero, as in zippity doo dah — role in the safety of those products.

Barb Ingham at the University of Wisconsin Extension says,

You may safely reduce or eliminate salt in all home canned tomato recipes.” ^[25]Ingham, Barbara. Home Canning: Can I Make Substitutions Safely? University of Wisconsin Extension. 23 June 2015. Accessed June 2016 at https://bayfield.uwex.edu/2015/06/23/play-it-safe-changes-and-substitutions-to-home-food-processing-recipes.

Home canned tomato product yields

Expect two to three pounds of raw tomatoes to convert to one quart of crushed tomatoes [Ed: 1 kg per 1 litre]. For tomato sauce, plan on four to five pounds per quart [Ed: 2 kg per litre]. For jam, chutney, ketchup and other long-cooking, thick preparations, it will take about eight pounds to make a quart. [Ed: 3 kg per litre]” ^[26]Barrow, Cathy. Tomato canning q&a. Washington, DC: Washington Post. 14 August 2012. Accessed June 2016. 

Further reading

Burtness, Carol Ann. Canning Tomato-Based Salsa Safely. University of Minnesota Extension Service. Reviewed 2018.  [/ref]

Browse site on all tomato canning topics

Home-canning tomatoes: how to

Acidifying tomatoes for safe home canning

Peeling tomatoes

Canning crushed tomatoes

Chili Sauce

Ketchup

Minnesota Mix

Spaghetti Sauce

Strawberry Tomato Jam

Tomato Sauce

More information on Green Tomatoes