Home preservers often wonder why USDA preserving recipes calling for lemon juice specify that the juice should come from a bottle. In most grocery stores the only such product used to be ReaLemon, which is made from concentrate and preserved with sulfites. Today a few competing brands of lemon-juice-from-concentrate are available, with similar assortments of preservatives. To most discerning cooks, ReaLemon and its imitators don’t taste quite real, and to people allergic to sulfites these products may be a health hazard. Bottled fresh lemon juice, with juice from Sicily or Peru, is available at some fancy grocery stores, but it also contains sulfites. Why shouldn’t home preservers use fresh lemons, which are inexpensive and available year-round in every supermarket? Is ReaLemon really better than real lemon?
Extension agents explain that lemons vary in their acidity, and that bottled lemon juice does not. To make sure your jam or your salsa–or, especially, your lemon curd— reaches a safe level of acidity, you should always use the bottled stuff, say the home economists. I decided to find out whether they’re right.
I first researched laws regarding bottled lemon juice. The Code of Federal Regulations (Title 21, volume 2, revised April 1, 2010), includes this FDA rule: Lemon juice prepared from concentrate, like ReaLemon, must have “a titratable acidity content of not less than 4.5 percent, by weight, calculated as anhydrous citrus acid.” Citric acid is the main acid in lemons. Lemons also contain some malic acid, but it usually isn’t measured separately. The ascorbic acid, or vitamin C, for which lemons are justly valued is destroyed by heat and so ignored in discussions of food processing. For our purpose here, we can say simply that lemon juice made from concentrate must have an acid level of at least 4.5 percent, and that the law allows this acid level to vary.
Hmmm. Even if the law allows a variable acid level, a manufacturer would settle on a standard, right? In the opinion of my husband, a chemist, that standard would be 4.5 percent. After all, water is cheap! Why would ReaLemon use more lemons than necessary?
I asked the folks at ReaLemon whether they standardized the acidity of their lemon juice and, if so, what their standard was. Here is their reply: “ReaLemon meets or exceeds the FDA standard of identity for lemon juice, which is 4.5% w/w.” This reinforced my husband’s opinion: ReaLemon had a standard acid level, and it was 4.5 percent.
We decided to test this hypothesis. I bought a bottle of ReaLemon, and we titrated the juice (I’ll explain in another post how to do this). ReaLemon tested at 4.9 percent—the “natural strength” of lemon juice, according to the label. The company rose in our estimation. They were exceeding a minimum standard!
If lemon-juice-from-concentrate is at least 4.5 percent acid, and sometimes 4.9 percent acid, what is the natural range of acidity in lemons? I posed this question to David Karp, a fruit researcher at the University of California, Riverside, who also writes for the Los Angeles Times. David referred me to Walton Sinclair’s Biochemistry and Physiology of the Lemon (University of California, 1984), a four-inch-thick summary of all scientific research on Citrus limon.
According to the research, some lemon varieties are more acidic than others. Lemons of a single variety can vary in acidity depending on the local soil and climate, the rootstock on which the tree is growing, the amount of fertilizer applied, and the season in which the lemons were picked. Lemons and other citrus fruits grown in hotter places, for example, are generally less acidic than those grown in cooler places. Both potassium and nitrogen fertilizers tend to increase acidity levels. New Zealand lemons are less acidic than California lemons, and California lemons are less acidic than Sicilian lemons.
Even a single lemon can show variations in acidity, depending on when you do the testing and from what part of the fruit you take the juice. California lemons increase their acid levels almost 25 percent during curing–that is, in the weeks of storage after harvest. One study found that juice from the stem end of a lemon is slightly more acidic than juice from the blossom end, and another study found that juice from the core area is slightly more acidic than juice from the periphery.
If all these variables make you think the home economists are right, think again. Although lemons vary in acidity, they generally don’t vary much. The least acidic lemon found among all those tested in dozens of studies, an uncured Eureka from California, had an acid level of 4.53 percent. The most acidic uncured Eureka tested at 6.50 percent, and cured Eureka lemons ranged from 5.71 to 7.42 percent. Lisbon lemons from California varied less, from 4.79 to 4.86 percent acid before curing and 5.25 to 5.32 percent afterward.
Florida lemons vary no more in their acidity than California lemons. In one Florida study, samples ranged from 5.16 to 6.41, in another from 5.24 to 5.92.
If you live outside the United States, the lemons in your market may be more or less acidic. In New Zealand lemons averaged only 4.9 percent acid, and in Italy lemons tested as high as 8.1 percent acid. But you won’t find lemons from New Zealand or Italy in Safeway or Albertsons.
Note that I’m not counting Meyer lemons as lemons. A cross between a lemon and an orange, the Meyer is relatively low in acid. Meyer lemons sampled in July averaged 2.4 percent acid in one study; those sampled in February and May averaged 4.1 percent acid.
With all this information before me, I guessed that the juice of a lemon from one of my local grocery stores would test at somewhere around 6.0 percent acid. It would almost certainly be a Eureka or a Lisbon (the fruits of these two varieties are hard to tell apart) or a clonal selection of one or the other. If it were a Eureka, it might be a little more acidic than 6.0 percent; a Lisbon might measure only about 5.0 percent.
So I bought a lemon, and my husband and I titrated the juice. It tested at 6.2 percent acid. Eureka! (Probably.) We drank some of the juice, too, and compared the taste with that of ReaLemon. The natural lemon juice was much less bitter (ReaLemon, like other varieties of bottled lemon juice, contains oil from the peel) and noticeably more sour.
Provided you start with regular lemons rather than Meyers, then, substituting fresh lemon juice for bottled in canning should be entirely safe, although the finished product might end up a little more tart than it would with bottled lemon juice.
Are you adding lemon juice to jam or jelly? This is done not for safety, generally—nearly all fruits are acidic enough for safe canning—but to ensure that the jam or jelly will jell. You can add a little less lemon juice than a recipe specifies if your fruit is quite tart, or a little more if you want a stronger gel.
If you’re canning tomatoes, the acidity of your lemons shouldn’t be a concern. Nearly all tomatoes are acidic enough to can without added acid. If yours are unusually dull in flavor, follow the USDA recommendation: Add 1 tablespoon lemon juice per pint of whole, crushed, or juiced tomatoes. Or, if you like, add more.
Recipes for canned salsa call for quite a lot of lemon juice (or lime juice, or vinegar). If you’re using several fresh lemons, their acidity will average out, and the average will almost certainly be higher than 4.5 percent. By using fresh lemons you may risk making your salsa a little too tart, but you can minimize this risk by using low-acid, paste-type tomatoes, such as Roma, which provide the additional advantage of making salsa thicker.
A particular concern of many home preservers is the safety of fresh lemon juice in canned lemon curd, a tart, buttery custard that’s used as a dessert topping and filling and as a spread for toast, pancakes, waffles, and so on. It’s essential to have a high level of acid in a protein-rich food that’s processed in a boiling-water bath. Home economists say that canned lemon curd is safe only if the lemon juice comes bottled, but remember: American store-bought lemons—the regular kind, not Meyers—are at least as acidic as bottled lemon juice. Besides, you may prefer to use more lemon juice in your curd than called for in the USDA recipe, which, I notice, contains proportionally less lemon juice than does my recipe in The Joy of Jams. You can find the USDA recipe here.
Lemon curd doesn’t need canning, of course. If you put it in a jar in the refrigerator instead, it will keep well for several weeks. You can also freeze lemon curd, and thaw it in the refrigerator for a day before you plan to serve it. If you have a lot of lemons and want to juice them right away, you might freeze the juice so you can make lemon curd as you need it. Lemon juice keeps very well in the freezer.
If you want to give your lemon curd as gifts, though, you may be set on canning it. In this case, be sure to follow the USDA processing instructions. Heat the water to no more than 180 degrees F. before adding the jars, and boil them for 15 minutes, or longer if your altitude is over 1,000 feet.
When you give a friend a jar of your homemade lemon curd or another preserve, you can feel proud that you’ve used the tastiest, freshest ingredients, and confident that your gift won’t prompt an allergic reaction to sulfites.
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This is such a helpful and interesting post! Thank you so much for getting to the bottom of this. I always adhered to using bottled lemon juice (I use Santa Cruz bottled lemon juice, which I like, but is expensive), but always wondered why. Now I know!
Excellent! Thanks for an interesting, and informative, post. So happy my backyard Eurekas meet the standard. 😉
Wonderfully informative article Linda! This one will go in my canning info file for reference!
Couldn’t agree more about the grocery purchased item ReaLemon tasting less than desirable. Makes me want to tap into a bio-chemist friend and test lemons from my Meyer tree. Some have been hanging a while. I didn’t know curing them increases acidity.
Linda, this is an absolute coup. Thanks for all your hard work and for putting to rest the uncertainty around using fresh lemons versus bottled. Truly excellent stuff.
Wow, this is a phenomenally informative post! I learned so much about acid and lemons. I don’t do a lot of canning but had wondered why some recipes called for non-fresh lemon juice. Thank you!
Ten years ago I planted a Meyer and I have access to Eurekas. Yay for lemons! I have the juice of one every morning in warm water. Yum!
Thank you so much for this! I am going to can several jars of curd to give away and I had been waffling about the safety issues. I hate the taste of bottled lemon juice plus the waste it creates.
Thank you for researching this topic so thoroughly! I always cringed as I added bottled lemon juice to my otherwise fresh and delicious concoctions, no more.
I’m amazed you would do titration for a just because. I detest titrations.
Geeky, smart, thorough, useful and a fun read… kudos! And many thanks!!!
WOW! I am actually agast that the USDA would recommend something artifical when the natural is as acidic or BETTER! It just goes to show how much facts are dummied down for the general public.
Thank you a million times over for taking the time to test this! (I am actually sensitive to sulfites, so I am soooo glad to find this!)
Is the USDA more inclined to support domestic farmers or consumers? I think the name explains it – Dept of Agriculture.
What a wonderful article! Did you ever measure the acid content of lime juice? I assume it’s in the safe range, but it would be interesting to know.
I’ve finally gotten around to doing a little research on limes. Citrus latifolia Tanaka, the Bearss, Persian, or Tahiti lime, is about as acid as a lemon, with a titratable acidity of about 5 to 8 percent. Citrus aurantifolia Swingle, the Mexican, West Indian, Key, or bartenders’ lime, has a titratable acidity of about 7 to 8 percent. So substituting lime juice for lemon juice should always be safe.
Thank you so much for this, I have limes here in Mexico, and they do not sell bottled LEMON Juice, limes are called limones which is so confusing to begin with. Tomorrow I am going to can Orange Marmalade with the peel in it, and use the lime juice from my trees (the classic mexican lime with seeds and very acidic). So excited to know I can do this, whew…I was so worried!
It would be a pity not to use your own delicious fruit, wouldn’t it?
I did my orange marmalade with orange peel in it today, first time ever canning! Used the lime juice for the added acidity, the tattler lids are down locked, and looks like I was completely sucessful with my 6 8oz jars! I am so happy lime juice is ok, and it tastes amazing, you would never know there was lime juice in there! Thank you Linda!
You’re welcome, Laura! I’m glad your marmalade turned out well.
Wow. What wonderfully thorough coverage. I am especially glad you provided the info about Meyer lemons, as we have a Meyer lemon tree and I typically substitute that fruit wherever lemon juice is called for. Thanks for all the great info.
Fab. My suspicion was that, like boxed pectin, industry had their hand in the marketing of the Real Lemon through extension agencies and home economic program everywhere. Somewhere around the early 40’s you can see the plethora of products that came on the market to usurp common sense. Certainly food preservationist were not spared the onslaught. So bottled “Real Lemon” took the place of the real lemons if only as a way to increase sales. But that was a hunch and not a great researched body of work like your own. Thanks Linda. You made us proud.
Thanks for affirming what I have felt all along in spite of the advice from the canning police to use bottled lemon juice. I use fresh lemon juice whenever lemon juice is called for in canning recipes, but still suffer a few guilt twinges because I wasn’t following correct protocol. BTW, I have both Joy of Pickling and Joy of Jams and Jellies in my preserving library and love both books. I think fresh lemon juice rocks!
Thank you, Sandra, and everybody else who has commented on this post.
Love this article thank you I only use fresh lemons but I am blessed to have a few lemon trees…thank you i will be back
Excellent. You’re the best, Linda. I’ll pass along this information and likely won’t use bottled juice again. Another view on why Extension folks might recommend bottled juice is, of course, to promote values of economy and efficiency, both at odds with wealthier, more organically/sustainability-inclined preservationists. Not saying either view is better.
This is interesting, but I will be interested to learn how you tested the acidity of the lemon juices; it was my understanding there was no accurate way to do this at home?
You can test acidity at home just as you would do it in a laboratory.
I love this. Thank you for expounding the confusing industry info & the geeky chemistry stuff that I most enjoy reading and then stashing away in my preservers arsenal!
THAT. was AWESOME! Thank you so much!
Linda, Thank you. I have always thought some of the USDA information was dubious. When I bought a pH meter to test recipes, I was told that this was dangerous for home canners. My thought is, the more science in the kitchen, the better. Now that you’ve resolved my long time lemon suspicions, I wish you’d take on some other canning issues.
I was told that I can’t use Clear Jel to make tomato sauce, because of viscosity. I have trouble following this line of logic, because the alternative is to keep cooking it until it’s thickened. This makes it lose much of it’s fresh flavor. I can’t figure out why it’s safe to can apples with Clear Jel, but not tomatoes. Apples are higher in pH, than tomatoes, and surely to make them into pie filling, they would be thicker than tomato sauce. But once I add the lemon juice to the tomatoes, there pH is raised to the safety level.
I very happy about the lemons. Let us know when you test the limes! Hooray, no more bottled juice.
I haven’t been inclined to use Clear Jel myself, but I’ll look into this question when I have a chance. In the meantime, maybe some other readers have thoughts about the safety of using Clear Jel with tomatoes?
“WOW! I am actually agast that the USDA would recommend something artifical when the natural is as acidic or BETTER!”
@Phoebe Adams – I’m not. Look up the “principle of substantial equivalence” on Google. While the USDA is a different Department from the FDA, there are rather corrupt people in both Departments. It is taking people like the author of this article who do REAL science to reveal the truth behind the lies.
I really enjoyed this post on acidity of lemons, I grew up with my grandma and mom canning massive quantities of food from the garden and not using any lemons or lemon juice at all. We must remember that canning was mostly traditionally used in countries where lemons don’t grow because it’s too cold (Poland, Sweden, Russia…) And people did just fine… I wonder how… (red currants?)
Currants, gooseberries, unripe grapes, cranberries and their relations–there are a lot of sour fruits in the world. Even in India, where lemons are native, people often use tamarind or green mango instead.
Minute Maid has a frozen lemon juice. It comes in a box in the freezer section. The yellow plastic bottle inside is supposed to be equal to the juice of 7 lemons. Any information on the acidity of a frozen lemon juice?
Thank you so much for this great posting. I really appreciate all the great info.
Thanks for this information, DeAnna. Since Minute Maid deals in juice concentrates, I’m guessing that Minute Maid frozen lemon juice is made from concentrate. If so, the juice should meet the titratable acidity requirement of 4.5 percent. Because this juice doesn’t have to be “shelf-stable,” however, it is probably free of sulfites. Can you check the label and let us know (1) whether the juice comes straight from lemons or from concentrate, and (2) whether any preservatives are added? The label should also tell you what country or countries the lemons come from, a concern of many shoppers (I hope).
Linda,
After reading your very informative article, I was thinking about asking you the same question about MM Frozen lemon juice. After picking up a couple of bottles, I can tell you this much:
1) The juice is reconstituted from concentrate
2) It says no preservatives were used in any stage (The ingredient list is purified water and lemon juice concentrate)
3) The concentrate comes from Argentina and is hydrated and packaged in the US
I hope this helps out. Thanks again!
(PS On a side note, 7.5oz is $2 in my neck of the woods, more expensive than ReaLemon, but worth it for me for the lack of chemical additives)
Thank you, TJ. Minute Maid sounds like another good alternative for people worried about sulfites.
We should all remember that we can freeze lemon juice ourselves, so we have some on hand even when the last lemon in the fruit basket has rotted. I sometimes freeze juice in ice-cube trays when lemons or limes are cheap and then store the cubes in a plastic bag in the freezer. Freezing fresh (unpasteurized, unconcentrated) juice preserves its vitamin C.
Remember the part about how heat destroys ascorbic acid? A good portion of the acidity of a fresh lemon comes from the ascorbic acid as well as the citric acid. I don’t pretend to know what the proportion of citric to ascorbic acid is in a fresh lemon, and I have no doubt that it varies with variety as well as growing conditions; but unless you have tested lemon juice AFTER it has been subjected to the type of heat processing that occurs during canning, I submit that you do not know how much acidity you have actually introduced to your canned goods.
Also you are incorrect in your statement that tomatoes should be “safe” because they are acidic enough on their own – many modern varieties of tomato are bred to be sweeter (hence less acidic) and they are not safe for non-pressure canning processes anymore. I’ve seen charts purporting to show that tomatoes are (barely) in the “safe” range of acidity, but again, these chart makers ignore the effect of heat processing on natural acidity due to the breakdown of various substances contributing to overall acidity.
I’ve been canning for nearly 50 years. When I was a child, we routinely canned tomatoes via boiling water bath, but I wouldn’t dream of doing that with modern tomatoes, or even heirloom varieties. There are some things I would still do, if my health were still up to canning, but many more I wouldn’t. For instance, jelly with paraffin toppers is safe if you have the right jelly glasses (smooth, slanted just ever so slightly flaring up from the bottom so air bubbles aren’t trapped) and you know what you’re doing; I believe this fell out of favor because doing it right took some skill and extra caution, whereas pressure canning really doesn’t. But boiling water bath canning tomatoes is one thing I wouldn’t do anymore.
I can’t speak to canning lemon curd; I’ve always made that fresh. But I wouldn’t ignore FDA warnings about the use of bottled lemon juice only during canning (things other than preserves and jelly) without evidence that acidity remains stable throughout the canning process.
Barbarian,
Although I don’t have figures handy, I can assure you that only a very small fraction of the acid in lemons is ascorbic acid.
When I describe a tomato as acidic, I don’t mean it isn’t sweet. Some tomatoes–the best ones, to my palate–are both very sweet–i.e., high in sugars–and very acidic. Only tomatoes very low in acid need added acid in canning. Adding acid to these bland-tasting tomatoes is most important when they’re canned with little prior cooking, because tomatoes get more acidic as you boil them down into sauce or ketchup.
The USDA approves the home processing of tomatoes in a boiling-water canner. And nobody is fussier about safety in home canning than the USDA.
Thanks for the information about sealing jars with paraffin. I’d never heard that this worked better in flared glasses. (Do others have opinions about this?)
Thanks for addressing one of my favorite topics…fear based cooking methods touted by governmental agencies. I do not want to be afraid of eating, cooking or preserving real food I grow or buy. Whenever I hear “you should never can this or that food” I am drawn to it like a moth to a flame.
I’ve always wondered about the lemon controversy. I pressure can a lot of stuff so never worry about acid levels with that method. But water bath canning needs to have some of this acidity stuff cleared up. When in doubt I have used granulated citric acid (in water) for acid in jams and jellies. (not my favorite method but I always have it on hand)
The other canning issue I’d love to see someone tackle is canning thick stuff like pumpkin, quince paste and fig paste. I would love to do that, but I do understand why so there may be no solution to getting and maintaining the internal temperature of the jar. I always wonder what the companies who sell pumpkin in cans or other thick purees do to make it safe.
Laura, what the factories have are high-pressure steam retorts that turn the cans continuously during processing.
Thanks for tackling one of my favorite topics…fear based cooking methods from governmental agencies. I don’t want to be afraid of using real food I grow or buy in canning. Whenever I hear “you can’t can this or that because it isn’t safe” I’m drawn to it like a moth to a flame.
I’ve always wondered about the lemon controversy. I pressure can a lot of things so don’t have to worry about acidity, but acid in water bath canning needs to be cleared up. I sometimes use granulated citric acid in a pinch since it’s always on hand in my cupboard.
One thing I am always searching for is a way to can thick purees like pumpkin, quince paste and fig preparations. There may be no solution to making sure the internal temperature of the puree is getting hot enough during canning but I can’t help but wonder how manufactures of these products can and jar them safely.
According to the National Center for Home Food Preservation website, the USDA recommends against canning pureed pumpkin because the agency hasn’t conducted studies to determine safe processing times. I’ve just written the NCHFP folks to ask when they might conduct such studies and share the results with the public. I’ll let you know if I get an answer. In the meantime, keep in mind that pureed pumpkin freezes really well.
It should be safe to can pumpkin butter in a boiling-water bath provided that the butter is sufficiently acidified. On this topic NCHFP writes, “Pumpkin butters produced by home canners and small commercial processors in Missouri have had pH values as high as 5.4. In fact, the pH values seemed to be extremely variable between batches made by the same formulation (Holt, 1995). The Holt reference refers to a personal email message; apparently Mr. or Ms. Holt tested a few batches but did not conduct a formal study of this subject. I would guess that the amount of lemon juice called for in the recipe was too low to cover variations in the acidity of the ingredients and the measuring skills of the canners. If you want to can your pumpkin butter, I suggest checking the pH.
This post was just shared with a canning forum i am on and I think its excellent.
However i suggest you add somewhere in bold a statement that one cannot use percent acid when comparing 2 different types of acid solutions (like lemon juice and vinegar). I think this is a common confusion and that someone may see the info about lemon juice having a percent acid of 4.5% and then conclude that vinegar with a percent acid of 5% is more acidic when in fact that is not the case since citric acid is a stronger acid than vinegar and thus more easily releases its acidic hydrogens into solution. Percent acid is absolutely the right way to compare solutions of the same acid but when comparing solutions of different acids and making conclusions about how acidic something is pH is the proper measurement
Also when doing the titration you are in fact measuring all the acids present – the sodium hydroxide will react with every type of acid in the solution. But since citric acid is by far the predominant acid when the percent acid is reported its assumed all that acid is citric acid. That is what the statement “calculated as anhydrous citrus acid” means. The only way to measure a specific acid is to separate out the components of the solution using a separation technique such as chromatography. Luckily someone has done that in a study looking at citric acid content as a way to treat people whose do not have enough citric acid in their body and they came to the same conclusion you did. More citric acid in fresh than bottled from concentrate. They did not use % acid w/w but rather g/L but the units are not important only the further support for the conclusion that fresh have more citric acid than bottled.
this is the paper that examines just citric acid – http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2637791/
Becky, thanks for making the point that we can compare the strength of different kinds of acid by pH but not by percent acid. Thanks also for the link to the article for which citric acid was measured using ion chromatography. Although the study was performed in the interests of people prone to kidney stones, I recommend that anyone doubtful about canning with fresh lemon juice have a look at tables 1 and 2, at least. The results do indeed confirm my findings.
Hallelujah! Thank you so much for mentioning one can check the PH of their pumpkin butter for safety. Every site I’ve visited (that addresses the issue) castigates anyone who even suggests testing at home. Usually it’s a master canner or some such, who says litmus paper and ph meters are unreliable. If that were the case, wouldn’t small, commercial concerns that can in their own kitchens be out of business?
I’ve been trying to reproduce some of my great-grandmothers old recipes. I use the ph meter and presume that is sufficient to determine acidity. Then I water bath and the next day check the acidity again (in leftover bits) after having made a slurry. Does this work or is there a better way to come up with our own recipes?
If you’re making pickles with at least one part 5% vinegar to each part water, they should be acidic enough. If you’re canning fruit, it should be acidic enough even in plain water, unless the fruit is figs or Asian pears. Testing with a pH meter is a good idea if you’re selling your canned goods or if you think you may have measured wrong.
Thank you so much for this information. I’m planning on making canned peach salsa (no tomatoes) tonight in the boiling water canner. The recipe calls for vinegar, but I’m now confident that I can substitute it with an equivalent amount of fresh lime juice. Vinegar in peach salsa doesn’t sound too appetizing.
“Real Lemon versus ReaLemon | A Gardener’s Table” was in fact a really awesome post, . Keep publishing and I’ll
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Thanks for clarifying this issue for all of us canners who have fresh lemons and limes on hand. I’m just about to make a batch of tomato salsa and all the recipes demanded bottled juice. I’ll have to look for your titration article next. Love the practical science.
Thank you for this great information! I will use real lemon juice from now on when canning salsa. I appreciate you having done the research 🙂
I just wanted to know if the plastic lemon is less nutritional? Which would be better for me to eat not use for canning ect. I want to eat better but I don’t do the grocery shopping. I was going to make a dressing out of it instead of using a canola oil, sugar, juice, preservative mix dressing. Use the bottled lemon, olive oil, salt pepper. Or would squeezing an actual lemon into it be better for me?
Kayla, the juice in the plastic lemon is no different than the juice in the tall bottle. This juice contains little or no vitamin C. A fresh lemon is always a better buy.
Would meyer lemons be safe if you tinkered around and added citric acid to the recipe?
Yes, Julie, you could certainly use a combination of Meyer lemon juice and citric acid in place of true lemon juice.
This question is what led me to your very informative post! I have a ton of meyer lemons and would like to make curd with them, but how much citric acid do I need to add to make it acidic enough? I have a very simple ph test paper that shows Ph levels from 3.8 – 5.4, I’m going to give this a try.
What a good question, Kelly. I think you could simply stir enough citric acid into your Meyer lemon juice until the pH has fallen to 2. Obviously, though, your pH paper, with its range of 3.8 to 5.4, won’t do for this test. It would be best to use an electronic pH tester.
I’ll let you know if I can get a better answer from my science advisor.
Thanks for your reply, Linda! I don’t think I’ll be investing in a Ph meter and I quickly determined that my Ph papers weren’t going to cut it. I might juice my meyer’s for now and wait to hear if you have any success 🙂
My science guy liked my suggestion. Maybe one day we’ll come up with recipe for lemon curd acidified with Meyer lemon juice and citric acid. In the meantime, you might be interested in this blog post about somebody’s experiments in neutralizing his alkaline well water with citric acid: https://mattgadient.com/2015/12/21/my-attempts-at-adjusting-ph-for-plants-with-vinegar-and-citric-acid/. His figures make it clear that you’d need very little citric acid to adequately acidify your juice. Unfortunately, I can’t say exactly how much you’d need.
Thanks for the link! I am bottling tomatoes today and it occurred to me that I could use a similar amount of citric acid to add to my lemon curd as I am adding to the tomatoes, ie 1/2 tsp per quart of tomatoes. I think I will make up a batch of curd with acid added, leaving one jar without as a control and see how that goes.
Question on canning tomatoes. You state that they’re acid enough to just can (and I agree!), but every single “official” set of instructions I can find says tomatoes should have additional acid added, even the pressure canning instructions! Do you know why by any chance? Is it concerns over the natural variations in the tomatoes? Other than picking up a titer setup like you describe is there a way to check the acidity of my tomatoes here at home?
You’re correct, Ruth: The reason the USDA recommends adding lemon juice or citric acid is that certain varieties of tomato are low in acid, with a pH higher than 4.6. Since the acid in a tomato is in the juice, low-acid tomatoes tend to be the meatier varieties, with small seed cavities. Although low-acid tomatoes are preferred by some people with stomach problems, these tomatoes taste bland to me. They are usually good for sauce and paste, however, because in boiling down the tomatoes you concentrate the acid.
You can measure the pH of your tomatoes by pureeing them and then using a pH meter to test the pH of the puree. This is a much easier process than titration. Or you can decide to trust your own taste buds.
Thanks! Doing a quick search it doesn’t look like a PH meter is horribly expensive. I’ve been freezing the tomato sauce from this year’s crop because I didn’t want to add any acid, but in the future it’d be nice to be able to save that freezer space…..
Thanks so much for all of your hard work. I love The Joy of Pickling and use it often. I can’t believe I just found your blog! I wish I had read this post yesterday. I just finished processing 5 quarts of San Marzano tomato sauce and am now regretting adding citric acid to them. Is there a pH meter that you recommend? I use one at work but it’s about $400 and requires fresh buffers to calibrate with each use.
I’ve had my pH meter for many years, and I don’t know how much it cost, though I would guess well under $100. It came from Cole-Palmer, a scientific supply company. The product is called a pH Testr [sic].
You might read some of the reviews of inexpensive pH meters on Amazon.com.
Thank you, nice timing, too. I have been using grocery store bought frozen lemon juice for many years but it’s getting hard to find. I now keep whole lemons in the freezer to be zested or juiced when I need one. Thanks for the very interesting post.
Thank you very much for your research. I have been sifting through articles on canning tomato soup and salsa, hoping to find an answer in regard to the acid level. What I don’t understand is why the professionals all insist on using “bottled” juice when there is no less acid in the freshly squeezed lemons. Most of us who can prefer to stay away from all the excess preservatives in the first place.
BTW, any idea if lime juice is as good as lemon for canning ratios? I’m assuming that freshly squeezed lime juice also measures up to the bottled variety.
JP, you can safely substitute fresh lime juice for lemon juice in canning.
I suspect that USDA recipe developers always use bottled lemon juice so that they get more consistent results, even though the main ingredients of their recipes–fresh fruits and vegetables–are liable to vary quite a lot from batch to batch. What I can’t understand is why Extension imposes the rule of bottled lemon juice on home canners–that is, on people who typically care more about good taste and healthfulness than about uniform results.
Agreed!
Great post! I’ve learned so much, thank you for that!
hey i am from Guyana i am looking for a lime market and wonder if you are interested in buying some or could help me in a market? please reply to my email!
thank you!
Nandinie, I can’t buy your limes or refer you to a buyer, but maybe someone reading this blog can help you.
Answered all my questions! Thank you for being so helpful!
I still did not get an answer to my question. I have a recipe that asks for a real lemon plus lemon extract. I want to know what the difference is and can i use just a real lemon
The lemon extract, made with alcohol, must be in the recipe for extra flavor, not for acidity. You should be able to safely leave out the extract.
Thank you!!! I don’t want to use bottled juice and was getting quite irritated with all the hype about using fresh juice in salsa. I appreciate your research and taking the time to post it.
Thank you so much for this helpful information. Do you have any information about the acidity, or pH, of ripe (yellow) limes that are sometime sold as sweet limes?
The Bearss lime and, especially, the Key lime will turn yellow with age, but the sweet lime is something else–something that I’ve personally never encountered. Here’s a link to the Wikipedia entry about this fruit: https://en.wikipedia.org/wiki/Citrus_limetta. According to the article, the fruit is called sweet because it is low in acid.
Where are the references to these studies (particularly the Florida lemon acidity)
Jenn, you’ll find all the references in Walton Sinclair’s Biochemistry and Physiology of the Lemon (University of California, 1984).
Very Interesting! Thanks for posting.
Wow! Great educational article!
Thanks for all the research. I make my own salsa for canning and have been trying to research all the acidity aspects because there doesn’t seem to be that many variations in the recipes. It is kind of like labs developed 10 recipes and then all they do is verify them at different universities. One thing I read is that to do a good ph reading on salsa you have to wait a day or to for all the ingredients to stabilize. Have you ever done that, even waiting until they are opened months down the road. The other issue I just can’t find info on is boiling down tomatoes. I think the acidity would increase since water is boiled off but that would be a good thing to measure.
Ralph, if you want to take a pH measurement quickly of something chunky like salsa you can purée a bit in the blender. Also, yes–I have measured the acidity of tomato sauce before and after boiling it down, and the acidity certainly does increase.
I used Nellie & Joe’s Key West lemon juice and my Lemon Meringue Pie was a little too tart….more so if I use fresh lemon juice. Is that unusual and should I just cut back on the amount of lemon juice in my pies?
Dianne, I think this is a matter of personal taste. In the several recipes I’ve looked at, the quantity of lemon juice for a 9-inch pie varies from 1/3 to 1/2 cup. So, if your pies are too tart, you should feel free to use less lemon juice. To avoid changing the balance of liquids to solids in the filling, you might replace the juice you’re leaving out with an equal volume of water. (By the way, this is not a food-safety question, since lemon meringue pie is meant to be stored in the fridge and eaten soon.)
What a great article! Thank you for your hard work. 🙂 Can I use similar techniques to test the pH of key limes and other citrus?
Yes, Sarabeth, you can use the same process, but keep in mind you will be measuring titratable acidity, not pH. Measuring pH is easier, and pH meters can be quite inexpensive.
Great article! Thank you for doing all that investigation and testing and sharing it!
Thank you so much for doing all of this investigative work and then publicly making the information accessible for anyone interested in knowing “the facts”. I will never buy that RealLemon stuff ever again.
Yes….. an unbearable one. I have a lemon tree in my front yard that is filled with lemons just begging to be put to use. I am sooooo glad that all I have to do is harvest them and let them sit for about a week. I will be using them in my canning from now on….. no more bottled junk!
You are so lucky, Kelly!
Bravo! After hours of trying to find a logical, scientific answer to the question why in the world is lemon juice in a plastic bottle better than a glorious fresh squeezed lemon I found a legitimate answer! I will be using what God gave us from here on out with confidence.
A simple precise solution would be to measure your lemon juice with a ph strip or device. However, all data within this page and USDA provided mentioned percentage acidity. If I knew what pH my lemon juice needs to be it would be easy to measure that. Anyone have any advice on this?
That’s a good question, Greg. Lemon juice has a pH of 2 to 3. If you have some bottled lemon juice on hand, you might check its pH. My article concerns titratable acidity because that’s the measurement that the FDA requires on bottles of lemon juice and vinegar. But in general titratable acidity is used more as an indicator of taste, and pH more as an indicator of stability and safety.