Many home preservers often wonder why tested and USDA approved canning recipes call for bottled lemon juice. This is especially true when it involves tomatoes and making jams. Why not fresh squeezed lemon juice?
A USDA RECOMMENDATION
It is a USDA recommendation that bottled lemon juice be used. And consistent with the recommendation, reputable canning sources will agree that the best source of lemon juice for canning is commercially bottled lemon juice, as opposed to the juice of a fresh lemon. The reason for the recommendation is that bottled lemon juice has been uniformly acidified or standardized per FDA regulations: “lemon juice prepared from concentrate must have a titratable acidity content of not less than 4.5 percent, by weight, calculated as anhydrous citrus acid.” With a guaranteed pH (5 percent2), there is a consistent and known acid level which is essential for the critical safety margin in canning low-acid foods and for making jams gel properly.
Acid strength is measured on the pH scale. The scale starts with strongest acid at 1 and declines in strength as the number increases to 14, the strongest alkali. The lower its value, the more acid in the food. The neutral point is 7, neither acid nor alkaline. The amount of acid in canned food is critical to deter the growth of micro-organisms and insure that the food is safe. Foods with a pH less than or equal to 4.6 are labeled “high-acid” foods. Those with a pH greater than 4.6 are “low- acid.” This distinction is very important because only high-acid foods can be processed safely in a boiling water bath. Low-acid foods must always be processed in a pressure canner; if not, they can support the growth of the potentially harmful bacterium, Clostridium botulinum.
The pH of fresh lemon juice is inconsistent due to variety, maturity, weather conditions during growth, soil, fertilizer, rootstock, and storage conditions. There are even variations in acidity within a single variety. Lemons grown in hot climates tend to be less acidic than those grown in cooler climates. Lemon juice contains both ascorbic and citric acid; since ascorbic acid is destroyed by heat, only citric acid is measured. The average acid level of fresh lemon juice is about 5 percent, thus the “natural strength” labeling on the lemon juice bottle.
While acid consistency is the reason for using bottle lemon juice, bottled lemon juice is made from concentrate and preserved with sulfites. For people allergic to sulfites, bottle lemon juice may be a health hazard. If you or family members have a sulfite sensitivity or allergy, substitutes for bottled lemon juice include bottled lime juice (not Meyer or key lime) or frozen lemon juice (not lemonade) in equal amounts as bottled lemon juice or citric acid in appropriate ratios. Citric acid, sold as a white crystalline powder and not the same as ascorbic acid, is available where canning supplies are sold. It can safely be used to acidify foods if used correctly. Vinegar should not be used to replace bottled lemon juice unless a tested recipe allows it because white vinegar is weaker in acid strength. Equal amounts of bottled lemon juice can be used to replace white vinegar in recipes calling for vinegar, but not the reverse. When vinegar is an acceptable substitute, it will affect the flavor of the food. Never change the amount of acid, dilute with water, or substitute acid sources unless the recipe specifically allows you to do so. Aspirin should not be used as a substitute in canning. It cannot be relied on to lower pH or prevent spoilage .
ACIDIFYING TOMATOES FOR SAFE CANNING
When canning products with an unknown pH as acid foods, they must be acidified to a pH of below 4.6 with lemon juice or citric acid. Tomatoes, usually considered an acid food, and figs are two examples where the pH values hover near or above 4.6. When acidified with lemon juice or citric acid, they may be processed as acid foods  making them safe for boiling water bath or atmospheric steam processing. Directions from the National Center for Home Food Preservation  for acidification of tomato products to insure safe acidity in whole, crushed, or juiced tomatoes state: Use 2 tablespoons of bottled lemon juice or 1/2 teaspoon of citric acid per quart of tomatoes. For pints, use 1 tablespoon bottled lemon juice or 1/4 teaspoon citric acid. Acid can be added directly to the jars before filling with product. Sugar may be used to offset the acid taste, if desired. 4 tablespoons of a 5 percent acidity vinegar per quart may be used instead of lemon juice or citric acid. However, vinegar will likely cause undesirable flavor changes. Tomato salsas must also be acidified. To get an idea of how much difference bottle lemon juice makes, see Table 1 in the publication Why Add Lemon Juice to Tomatoes and Salsas Before Canning? by North Dakota State University.
pH MATTERS WITH JAMS
While many factors are involved in getting jams to “set” or gelatinize, pH plays a key role. When fruit is cut and heated with sugar, pectin strands are released from the fruit cells. The freed pectin strands repel each other because they carry a negative electric charge. Lemon juice lowers the pH of the jam mixture and neutralizes the negative charges on the strands of pectin allowing them to move together into a network to “set” the jam. The optimal pH for gelatinization is between 2.8 and 3.5. The best way to achieve this level of acidity is to use commercially bottled lemon juice. A second reason for using bottled lemon juice in jam recipes is to prevent the growth of bacteria and insure safe canning. With a lower pH, jams can be processed in a boiling water bath for a small amount of time dependent on altitude.
Whether using bottle lemon juice to acidify tomatoes or getting jam to “set,” bottled lemon juice has a ‘best used by’ date. Keeping the product in the fridge may extend its date but it is best to use a fresh bottle when canning or making jam to insure that the juice is at its best.
The verdict is in. The best way to insure a safe or desired pH for canning low-acid foods or jam gelatinization is to go with a commercially bottled lemon juice. Bottled juice is controlled and standardized with the acid content assured and more reliable than fresh lemons. Fresh lemons, however, make excellent lemonade!
1 Code of Federal Regulations (Title 21, volume 2, revised April 1, 2010)
2 Green, Janet; Hertzberg, Ruth; Vaughan, Beatrice (June 2010). Putting Food By, Fifth Edition (p. 119). Penguin Books Ltd.
21 thoughts on “The Case for Bottled Lemon Juice in Canning”
I have a peach tree that is half yellow a half white. Presently have abundance of white peaches. I made jam last year with no problem. Now reading about possible botulism in canning. Can I add enough lemon juice to make this patch safe
Hi Eva, There is NO SAFE way to preserve white peaches except by freezing. White-fleshed peaches have a natural pH above 4.6, which makes them a low-acid food; therefore, water bath or atmospheric steam canning will not destroy harmful bacteria in white peaches. Also, at this time there is no low-acid pressure canning process available for white-flesh peaches nor a researched acidification procedure for safe boiling water canning of white peaches so please don’t try adding lemon juice thinking it will make your jams or anything other shelf-method safe. Freezing is the only recommended method of preservation for white peaches at this time.
Do you have to add lemon juice to pressure canned tomato sauce?
It is critical when home canning tomatoes, whether they are whole, crushed, juiced, salsa, or sauced to acidify them during the canning process. Adding the recommended amount of lemon juice (or citric acid) lowers the pH of all tested varieties enough to allow for safe boiling water bath canning.
Thanks so much for the information, Marlene! I have two questions. Can you use fresh lemon juice if you test the juice with litmus paper prior to determine the pH? I realize this is different from titratable acidity, but maybe there is a back calculation.
Second question, I’m new to canning, but if you do wish to use fresh lemon juice, say in a salsa recipe, can you choose to pressure can instead of using the hot water bath method?
Hi Sandi, If you can be sure that the lemon juice has an acidity of 2.0-2-6, it may be okay to use. This level of acidity is likely not accurately determined with litmus paper. To find the specific pH of a sample, you will need a pH test paper or pH meter. One should ALWAYS follow a canning recipe exactly as it is written and process accordingly. Tested recipes have been duly tested for pH and temperature needed to kill bacteria for the density of the product. When there is alteration in ingredients and one simply changes canning methods, one is on a very uncharted/unknown path. We would not recommend as there is no conversion chart for such.
Hello, I screwed up and added the lemon juice to my sauce instead of the individual jars. Do I still need to add the 2Tbl of lemon juice to the jars? Help!
My son is allergic to citric acid. According to the article I can substitute with frozen lemon juice. Is this found in concentrated form or something else? Thank you for the clarification of this.
Hi Sara, Frozen lemon juice found in the freezer case can be used but you need to make sure that it is concentrated or a pH of 2-3. If it is just frozen fresh lemon juice, the pH may not be low enough.
My question is about bottled lemon juice. I used Pomona Pectin and I made blackberry and blueberry jam. The recipe called for lemon juice. On the instructions it just said it is best to use bottled lemon or lime juice for the acidity content. My question is I used Santa Cruz organic 100% lemon juice NOT from concentrate. Will that be okay or do I need to throw away my jam? I actually made the jam back in August and just ran across an article which stated about using concentrated lemon juice and jam making:(. Thank you.
Hi Suzanne, Thank you for your question. Lemon juice is not used for food safety in jams and jellies; rather it is used to help the jam or jelly gel. I do hope that your jam gelled but even if it didn’t, the jam would be safe if you used a tested recipe and followed the directions including water bathing for the appropriate times for your altitude. I could not find the pH of Santa Cruz organic 100% lemon juice so I can not verify that it would be safe to use with foods that must be acidified for food safety. If you can tomatoes, for example, I suggest that you use Real Lemon/Lime or similar as the pH for these products is known.
Thank you Marlene. I also had emailed Pomona Pectin and they responded really quickly! They said that Santa Cruz is their choice of lemon juice. I did not realize that lemon juice in jam recipes was just for gelling, and yes they did gel. Thank you again for your response.
Thank you, Suzanne, for the reply and letting us know that Pomona Pectin chooses Santa Cruz as their lemon juice of choice. Good to know.
Should lemon/lime juice be added to the jars of salsa prior to the salsa being added or can it be added to the salsa during preparation?
Hi John, that you for trusting AnswerLine with your question. The lemon or lime juice should be added to the jar before adding the salsa; it should not be added to the salsa during preparing. It is very important that the right concentration of acid be present in each jar to assure that the tomato product is unqestionably safe assuming that a tested recipe and procedure has been followed.