Citric acid and home canning

Citric acid is a concentrated powder that raises the acidity level of a food or solution it is added to. It also may slightly help in better keeping qualities for flavour and colour.

Its use in home canning is endorsed by the USDA:

Citric Acid: A form of acid that can be added to canned foods. It increases the acidity of low-acid foods and may improve the flavor and color… The acidity level in foods can be increased by adding lemon juice, citric acid, or vinegar.”  ^[1] United States Department of Agriculture (USDA). 2015. Complete guide to home canning. Agriculture information bulletin No. 539. Page 1-8

In the USDA Guide, the use of citric acid is largely suggested with items such as tomatoes, just to give them a good shove into a very safe high acid / low pH range.

The molecular formula is C6H8O7; the E number is E 330.

How can citric acid be used for acidity in home canning?

The Putting Food By authors go into citric acid in some detail:

Citric acid. Pure crystalline citric acid, USP (meaning ‘United States Pharmacopoeia’ and therefore of uniform stability and quality), is the acid added in canning tomatoes when bottled lemon juice is not used. If you buy it as ‘sour salt’ or ‘lemon salt,’ that is, as coarse crystals, crush it to the consistency of finely granulated sugar before measuring. It is not expensive—especially when you consider that 4 ounces will do about 45 quarts, or slightly more than 90 pints of tomatoes. Citric acid is preferred for increasing acid-strength of foods because it does not contribute flavor of its own to food (unlike lemon juice and vinegars, which can alter flavor if used in large enough amounts). Fine citric acid may be substituted for a 5-percent acid solution (the average for store-bought vinegar or for the juice of most lemons) whenever the called-for measurements of the solutions are by the spoonful, in this general proportion: ¼ teaspoon citric-acid powder = a generous 1 tablespoon of 5-percent lemon juice/vinegar; ½ teaspoon citric-acid powder = a generous 2 tablespoons of the vinegar or lemon juice. (The equivalents actually are ¼ = 4 teaspoons, and ½ = 8 teaspoons, but 1 and 2 tablespoons are easier measurements to make in the usual household’s kitchen.) To reverse the coin and make a 5-percent solution of citric acid, use the rule of thumb for making salt brines: dissolve 1 part fine citric acid in 19 parts of boiled (and cooled) water. Translated into measurements used in the average kitchen, this means dissolving 2 tablespoons fine citric acid in 1 pint (2 cups) of boiled water; or, if you want to be metric, dissolving 30 mL of fine citric acid crystals in ½ liter (500 mL) of boiled water. Either translation will produce a solution around 6 percent instead of 5—but the result will serve the purpose we’re after.”  ^[2] Janet Greene, Ruth Hertzberg, Beatrice Vaughan. Putting Food By. New York: Penguin. 2010. Page 40.

Note a few things from the above excerpt:

• ¼ teaspoon citric acid = 1 tablespoon bottled lemon juice;
• “To… make a 5-percent solution of citric acid… [dissolve] 2 tablespoons fine citric acid in 1 pint (2 cups) of boiled water; or, if you want to be metric, dissolv[e] 30 ml of fine citric acid crystals in ½ litre (500 ml) of boiled water. Either translation will produce a solution around 6 percent instead of 5 — but the result will serve the purpose we’re after.”

Note that in terms of preventing fruit, etc, darkening, ascorbic acid is actually still better:

Volume for volume, [citric acid is] about one-third as effective as ascorbic acid for controlling oxidation (darkening), and therefore enough to achieve the same result could mask delicate flavors of some fruits.”  ^[3] Hertzberg, Ruth; Greene, Janet; Vaughan, Beatrice (2010-05-25). Putting Food By: Fifth Edition (p. 36). Penguin Publishing Group. Kindle Edition.

A little citric acid goes a long way. It works out cheaper to use than bottled lemon juice: when you buy bottled lemon juice, you are paying for a lot of water, not to mention the shipping costs and storage space for that weight.

Citric acid is sold under various brand names such as Ball, Mrs Wages, and many, many other brand names.

It’s good for those who don’t want the taste of either vinegar or lemon in their canned goods.

Citric acid lowers the pH without changing the tomato flavor like lemon juice.”  ^[4] Ball Citric Acid product description. Accessed March 2015 at https://www.freshpreserving.com/products/tomato.

Citric acid is actually more powerful than lemon juice

This table shows that citric acid is actually more effective at reducing the acidity of tomato products to be canned, than the standard 1 tablespoon of lemon juice. This is NOT to say that you should use citric acid instead of lemon juice: it’s just to show that yes, citric acid is as safe if not more so even than the lemon juice treatment.

Different forms, granular citric acid versus ground citric acid

Citric acid comes in a either a coarse granular crystal form, or a more finely ground crystalline powder form. When ready for home canning use, it looks like finely granulated sugar or table salt.

The Putting Food By authors say,

Except at drugstores, where it is often finely granulated, it comes as coarse crystals. The large crystals are easily pulverized between the nested bowls of two spoons or with a mortar and pestle….”  ^[5] Hertzberg, Ruth; Greene, Janet; Vaughan, Beatrice (2010-05-25). Putting Food By: Fifth Edition (p. 36). Penguin Publishing Group. Kindle Edition.

and

If you buy it as ‘sour salt’ or ‘lemon salt,’ that is, as coarse crystals, crush it to the consistency of finely granulated sugar before measuring.”  ^[6] Janet Greene, Ruth Hertzberg, Beatrice Vaughan. Putting Food By. New York: Penguin. 2010. Page 40.

Some master food preservers also advise people that it’s this ground up, granular form that you want to be using and measuring.  ^[7] “Linda Lou” Master Food Preservers Program Assistant. Washington State University Extension. In Garden Web discussion forum. October 2011. Accessed March 2015

The USDA doesn’t specify how fine a grind to use, so people assume that either form is valid even though their volume would measure out slightly differently. Nor does the USDA give the citric acid measurement in weight, even though they almost certainly, some people say, work in weight in grams in their labs.

What recipes call for citric acid?

Even though a little citric acid produces a lot of acidity, and it’s easy to use, and approved, it’s surprisingly actually not drawn on much.

Tomatoes and tomato mixtures are one of the few instances where the USDA draws on citric acid. For tomatoes and tomato mixtures, the standard acidification is:

• Per half-litre (US pint) tomatoes either ¼ tsp citric acid OR 1 tbsp lemon juice;
• Per 1 litre (US quart) tomatoes either ½ tsp citric acid OR 2 tbsp lemon juice.

The same ratio is drawn on by Minnesota for their now-famous “Minnesota mixture.”  ^[8] Burtness, Carol Ann. Tomato Mixture – Minnesota Style. University of Minnesota Extension. 2014. Accessed January 2019.

The USDA Guide (2015) draws on the use of citric acid in only two other places.

1. Figs

Add 2 tablespoons bottled lemon juice per quart or 1 tablespoon per pint to the jars; or add ½ teaspoon citric acid per quart or ¼ teaspoon per pint to the jars.”  ^[9] United States Department of Agriculture (USDA). 2015. Complete guide to home canning. Agriculture information bulletin No. 539. Page 2-14.

Note: this applies to whole figs, not puréed figs. They specifically say a few lines down, “FRUIT PUREES: Important: These recommendations should not be used with figs… .There are no home canning recommendations available for purees of these products.”

2.  King and Dungeness Crab Meat

Add ½ teaspoon of citric acid or 2 tablespoons of lemon juice to each half-pint jar, or 1 teaspoon of citric acid or 4 tablespoons of lemon juice per pint jar…. “Crab meat canned according to the following procedure may have a distinctly acidic flavor.”  ^[10] United States Department of Agriculture (USDA). 2015. Complete guide to home canning. Agriculture information bulletin No. 539. Page 5-9

To be clear, in this recommendation the citric acid is not there for safety. The safety comes from the crab meat being pressure canned. Instead, the acidification is there to help prevent too much discoloration of the crab meat, and citric acid is preferred over lemon juice for that acidification to help reduce the chance of changing the delicate flavour of the crab meat.

Dr Sonja Konkel from the University of Alaska Extension explains,

The problem is that the crab meat will discolor without the addition of some acid. Generally, the meat will take on a grayish hue. Adding citric acid or lemon juice prevents the meat from discoloration….” ^[11]Konkel, Sonja. Health, Home & Family Development Program for the Cooperative Extension Service UAF Juneau District. In Capital City Weekly. Juneau, Alaska. 5 August 2009. https://www.capitalcityweekly.com/stories/080509/hea_477905748.shtml

Note that the crab meat may still turn tan instead of white. But, it won’t turn the brown or dark grey that it would have without the citric acid. And, note that some people still think the taste is too acidic. For that reason, many Extension people suggest that freezing crab meat may be the better option for a lot of people.

Citric acid is not a magic bullet

Note that adding citric acid to something does not “permit any fiddling with canning methods.” The Putting Food By authors have anticipated that thought and headed us off at the pass on that one:

Acid is … added only to the foods…before canning them by the methods specified and for the specified processing time. The added acid does not allow any shortcut for any step in safe canning procedure….”  ^[12] Janet Greene, Ruth Hertzberg, Beatrice Vaughan. Putting Food By. New York: Penguin. 2010. Page 39.

What is the shelf life of citric acid?

Shelf life estimates vary. We’re sorry there is no clear answer here. You will have to review the following make your own mind up.

The Cargill Company in Iowa is a manufacturer of it; they sell in quantities of 25 kg up to 1 ton. Likely some retailers buy from them and repackage it in more consumer-friendly sizes. They say that after 5 years, “re-evaluate the product”:

Cargill Citric Acid is available as translucent white crystals…. Shelf Life and Storage: We recommend that product held for more than 5 years be reevaluated for fitness of use. Anhydrous [Ed: meaning without water] Citric Acid is slightly hydroscopic and should be stored under conditions of low temperature and low humidity in airtight containers to prevent caking.” ^[13]Citric Acid Anhydrous Product Information. Cargill. Updated 30 November 2010. Accessed August 2017 at https://www.cargill.com/doc/1432075932601/citric-acid-technical-data-sheet.pdf

Murphy and Son Co. in England imports theirs from China, reselling it in bulk, and estimates that “the shelf life at the recommended storage temperature is at least 1 year from the date of manufacture.” ^[14]CITRIC ACID ANHYDROUS (E330) Technical Information Sheet. Accessed August 2017 at
https://www.murphyandson.co.uk/Datasheets/CITRIC%20ACID%20ANHYDROUS.pdf

The European Food Safety Authority says four years:

The proposed shelf life of citric acid is four years when stored in a well-ventilated space under dry and cool (25 °C) conditions, protected from sources of heat or direct sunlight.  This recommendation is supported by analyses carried out on three commercial batches of anhydrous citric acid (C1), stored for four years at < 30 °C and < 70 % relative humidity (RH), in absence of light and in the original packaging (25 kg multi-layer paper bags with polyethylene (PE) coating). No degradation of the acid was shown over the proposed shelf life of the additive (100.0 vs. 99.9 % w/w). The Panel considers that the stability of the monohydrate would probably be similar to the anhydrous form. In another experiment with three batches of citric acid anhydrous (C2), virtually no degradation of the acid (99.9 to 100.0 % w/w) was seen after two years of storage at 25 °C and 60 % RH in a simulated selling package. ^[15]Scientific Opinion on the safety and efficacy of citric acid when used as a
technological additive (preservative) for all animal species. EFSA Journal 2015;13(2):4009. Accessed August 2017 at https://onlinelibrary.wiley.com/doi/10.2903/j.efsa.2015.4009/pdf

Many other manufacturers, such as ChemChed of Wisconsin, and The Chemical Company of Rhode Island give no date limit in their technical specifications sheets. ^[16] Citric Acid Anhydrous Spec TCC. Accessed August 2017 at https://thechemco.com/chemical/citric-acid/ and https://www.chemceed.com/wp-content/uploads/2015/11/Citric-Acid-Anhydrous-USP-Sales-Specs-00.pdf

At least one Master Food Preserver, the moderator of the Houzz Harvest Forum, says he treats the shelf life as indefinite:

There is no expiration date for citric acid IF it has been stored well and kept dry. If it has clumped or solidified toss it. If it is still in its normal dry powdered form it is fine to use. Proper storing is defined as in an air tight dark container (not glass or plastic), kept dry and not exposed to heat.” ^[17]User digdirt2. Moderator of Harvest Forum, Houzz. 22 July 2013. Accessed August 2017 at https://forums.gardenweb.com/discussions/1947375/how-long-will-citric-acid-last

When you buy yours, it will have been repackaged from the huge bulk shipping packages down into smaller consumer sizes by various retailers and resellers. Those people may or may not stamp a best-before date on it. As in all things with best-before dates, how they determine the date is up to them, and there may not necessarily be any rhyme or reason to it. Some resellers (such as the one shown in the lead photo on this page) don’t put a best before date on it.

[Note there are also liquid forms of citric acid which are used by large food processors, but we are referring to the solid crystalline powder form (“anhydrous”) here.]

Other uses for citric acid

The King Arthur Flour Company suggests:

• Just ⅛ to ¼ teaspoon per loaf will give your sourdough a wonderfully assertive tang.
• Add a tablespoon to your dishwasher to clean and delime it; also works for coffee makers. ^[18]Accessed August 2017 at https://www.kingarthurflour.com/shop/items/citric-acid-sour-salt

Where to buy citric acid

Like most things, citric acid can get cheaper the larger the quantity you buy. There are many different brands. Here are some Amazon links to help you get a feel for what’s out there. As with anything on Amazon, do compare prices because some vendors ask bizarrely high prices for a product that a vendor on the next page will be selling for a tenth of the price.

Also note that some brands may be packaged in facilities that also process eggs, dairy, peanuts, soy, tree nuts, and wheat. If this is a concern to you (for instance, if you are planning to market your home-canned product), be sure to grill the vendor first before purchasing.