Canning 101: Understanding Acid and pH in Boiling Water Bath Canning

September 19, 2013(updated on January 29, 2019)

pickles on a table

Today’s post is inspired by a rash of questions I’ve gotten recently in regard to my recipe for Honey-Sweetened Peach Vanilla Jam. A number of you are concerned because while that recipe contents lemon zest, it doesn’t contain any lemon juice. That jam is safe as written, but we need to dig a little deeper into canning science to understand why. Read on! 

If you’ve been canning for any length of time, you’ve probably heard mention of acid levels in relation to safe boiling water bath canning. Anything that is preserved in a boiling water bath must have a high acid content. The reason that high acid levels are important is that the presence of acid inhibits the germination of botulism spores into the botulism toxin. Botulism spores can only develop into the botulism toxin in low acid, oxygen-free environments.

When you preserve something in a boiling water bath canner, you heat the jars and their contents to the boiling point (that temperature varies depending on your elevation, but at sea level the boiling point is 212 degrees F). That heat is enough to kill off the micro-organisms that can cause spoilage, mold, or fermentation, but it’s not enough to kill botulism spores (they require far higher temperatures). The process of boiling the jars also helps to drive the oxygen out of the jars, creating a vacuum seal. For jars that have sufficient acid content, the result is a jar of food that is safely preserved and shelf stable.

The way food scientists (and home canners) determine whether something is high or low in acid is by pH. If something has a pH of 4.6 or below, it is deemed high in acid and is safe for boiling water bath canning. If the pH is 4.7 or above, it is considered low in acid. We’ll talk more about how to preserve those foods that are low in acid and have a pH of 4.7 or above another day, but to give you just a hint, that’s often where a pressure canner comes in.

If a food is close to the 4.6 pH point, you can often add enough acid to bring that product into the necessary safe zone. Fruits like tomatoes, figs, asian pears, melons, persimmons, papaya, white peaches and white nectarines, and bananas are often just a bit too low in acid in their natural state for safe canning. So in order to lower the pH to a safe level, we add either bottled lemon or lime juice, or powdered citric acid to products featuring those ingredients. Once the acid levels are high enough to inhibit the botulism spore’s ability to germinate into a deadly toxin, that product is safe for boiling water bath canning.

However, there are a world of foods out that naturally have a pH that is well within the zone for safe preservation in a boiling water bath canner. Here’s where we come around to the peach jam I mentioned in the introduction to this post. That recipe specifically calls for yellow peaches, which typically have a pH of 3.4 to 3.6. Charts like this one allow you to check on the general pH chart for various fruits and vegetables.

You could certainly add lemon juice to my jam in order to balance the flavor and add a little extra pectin (citrus fruit is naturally high in pectin), but it’s not necessary for safety.

Updated to add: One last thing! It’s important to remember the pH of the entire jar counts here. This is why it’s so vital to follow tested, reliable recipes for things like tomato sauce or salsa. Sure, you can add bottled lemon juice to your tomatoes to lower the pH, but if you’ve also added onions, garlic, and basil to your sauce, you’re not just balancing the acid of the tomatoes, you’re also taking the rest of the ingredients into account. That’s why salsa recipes designed for canning contain so much bottled lemon or lime juice, or vinegar.

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125 thoughts on "Canning 101: Understanding Acid and pH in Boiling Water Bath Canning"

  • Great information — and thanks for the FDA link. So, if you want to find out the acidity of a specific recipe do you use the chart and and lot of arithmetic (not my strong suit) or get some litmus paper (I don’t even play a chemist on TV) or ??? Realizing, of course, that if there is any doubt, don’t do it.

    I do like to can salsa, though. Most recipes measure cups instead of weight, so I’m always wondering if I’m chopping onion or peppers or cilantro to the right size and how densely the cups should be packed. The vinegar and lime juice certainly help, but I do wonder.

    I made some green tomato salsa last year that was pretty good, at least initially. Everything sealed properly and stayed sealed, but six months in when I opened a jar it tasted of mold. Yikes!! Of course I threw it out, and wondered if the mold had been there in some of the tomatoes early on (I picked them in late Oct. when it was clear they weren’t going to ripen on the vine. It had been one of those Oregon Summers). I know you can’t taste botulism, and the moldy taste didn’t disrupt my digestion, but kind of freaky none the less.

    Maybe one day I’ll get brave enough to try pressure canning…

    1. The big problem with mold is that as it grows it raises the pH of the canned-good allowing growth of the C. botulinum bacteria (which cause botulism). Any sign of mold in a jar and definitely thrown it out.

      1. Mold can’t grow in a sealed container, so it’s more likely the mold was already there. The other possibility is that the seal was not set – but you didn’t mention this.

    2. Pressure canning is easy! Ball can sell you a really nice one with a ton of recipes for around 250 bucks. I hot water bath can my homemade barbecue sauces since they are tomato and vinegar based, but for my sauces made primarily with fresh peppers and fresh garlic pressure canning is the way to go and very easy. my canner simply has added weights and additional seals to add between 10-50 extra pounds of pressure to put your food over 250 degrees — the magic number for killing botulism spores!

    3. This conversation is very helpful, but I highly recommend people check out this other site for an excellent conversation on accurately testing the pH when canning. As a person who has done a lot of water bath canning over the years, with no testing, but use to work in a lab, I appreciate the detail they’ve gone into in explaining all of the ramifications.

  • If you have canned something and are curious as to whether its ph level was safe when canned, can you test the ph level when you *open* the jar later on? What I mean is, can you open it, use litmus paper to test it? Would the reading from the paper be enough to determine whether the ph when canned was enough?

    1. You can find some wonderful digital pH testers on eBay for very good prices. It’s re-useable and accurate. And you could certainly test the pH after you open it and yield a result.

    2. You COULD test it after opening…. but doesn’t that waste a lot of time, a lot of effort, and a lot of storage space? By testing it prior to canning, you can adjust pH levels NOW to ensure safe storage of your product. Digital pH readers only cost a few bucks, very easy to use, and will take any/all guess work out.

        1. My understanding is that the density of individual food pieces in a canned product must have the appropriate PH of 4.6 or lower to be safe for waterbath canning. When you use a ph meter, how do you test the product? If it is homogenous like jelly, that’s pretty easy but if it is chunky like say, spaghetti sauce do you just test the thin liquid or do you have a way of testing denser chunks of carrot or tomato? I am currently in talks with a lab in San Francisco in the hopes of getting a recipe tested. I have a recipe i love that I am pretty sure is not safe for waterbath canning and I really want to see if I can get it safe with a few tweaks. If I could do this with a PH meter instead of pay the lab, that would rock but it is big slices of peppers. Do I puree the peppers first and then test them with a PH meter? everything I have read from “official sources” has warned against using PH meters as there are too many variances such as food density.I really want a PH meter to be the answer but I am just not sure.

    1. My understanding is that bottled lemon juice is required to have a specific, consistent ph level, while fresh lemon juice can be inconsistent due to natural differences.

    2. Bottled lemon juice has a established ph level. Fresh lemon juice varies from lemon to lemon, therefore there is no way of knowing what the ph level is. So if you are adding lemon juice to increase your ph level, you need to use the bottle lemon juice. Hope that helps.

  • Thanks for this Marisa. It’s great to get a refresher course now and again. It helps me to hear it in simple terms that I can explain to others who are new to canning in a way that makes sense and keeps them safe.

  • The FDA list is nice, but doesn’t include white peaches or pears of any sort. Is there a better list somewhere, or do you test them yourself?

    1. There are other lists. If you search for “pH of common foods” you’ll find a number of them. I have done some pH testing in the past, but typically try to find information developed by others before resorting to that.

  • Thanks Marisa 🙂
    I’m new to canning and checked out your “Food In Jars” book from the library. I am flooded with cherry tomatoes this year and was thrilled to see you had recipes that didn’t require peeling and seeding. I plan on trying your basic tomato salsa and the roasted corn salsa. Being new to canning, I appreciate that your recipes are for smaller quantities … I was dreading having dozens of jars of something that I might not have liked.

  • Hey Marisa – did you mean higher the acidity? “Sure, you can add bottled lemon juice to your tomatoes to lower the acidity, “

    1. Maybe she meant “lower the ph?” I think raising the acidity lowers the ph – if I’m remembering my chemistry correctly.

      My question is this – can one use litmus paper as a good test to decide if one could use water bath canning for something, or is this not reliable enough? I made the roasted tomatillo salsa from your recipe on this site, which was delicious, but I did not can it, per your caution. I then made another one designed for canning – it had a lot of vinegar and, while good, was not as delicious as the first one. I would have loved to have canned the first one. Seems to me a litmus test would be good enough – but maybe not?

      1. Thanks for catching that, folks. I did mean “lower the pH” and I’ve fixed my error.

        As far as using litmus paper to test pH, it can be done. I recommend checking out the book Putting Up. It’s got instructions on how to use litmus paper to test acidity.

  • Great information! Wish I would have read it last week. I canned some homemade chicken broth, after reading it looks like I should have used a pressure canner and strained thru a cheesecloth- neither of which I did. I took my fresh broth (fat and all) and canned it for 30 min in a boilng water bath. I am pretty new to canning as I have made and canned a few salsa’s and some relish but this is what I get for trying something new! LOL Any help would be great! Thanks

    1. I just wanted to mention here that the straight-walled canning jars have a fill line near the top so that you can safely freeze things like broth without shattering the jar. I use them for sauce and stock all the time and they’re nice and neat in the freezer compared to trying to freeze in ziplocs or other stackable containers that aren’t designed for the freezer. Sorry your broth was lost to the canning process this time!

  • Have you found a source for the pH of seasonings/spices etc?

    I want to make a batch of the tomato sauce from Animal, Vegetable, Miracle — I think you’ve mentioned making it here in the past — but the recipe calls for “2 TBSP GROUND LEMON PEEL” and I’d like to use orange peel instead, since I love the taste and I have a whole jar of orange peel on hand but no lemon peel. I can’t find a source on the pH of those to tell me if this is a safe substitution.

  • This is the second year I’ve canned tomatoes without adding lemon juice. It seemed fine last year, but should I re-can this year’s tomatoes with lemon juice?

  • In order for me to sell my jellies at the local farmer’s market, I have to keep record of the pH of every batch of jelly. A food-grade pH meter can give you the pH of anything you want to can in just a few seconds. I got mine for < $50. Considering the amount of canning I do, it was a great investment.

    1. Hi Marc, could you inform us which good grade pH meter you purchased at that great price? Would be a good investment for some of us, thank you

      1. Sure Sande. I use the “Checker by HANNA Instruments”. The model number on the Hanna Instruments website is 98103. It gives an accurate pH reading in a matter of seconds. One can search the internet for a source other than HANNA. I purchased mine through Amazon for $35. There is an extra cost for the calibration solutions and storage solution. One should calibrate the meter each time it is taken out of the box to use it. One word of caution; never submerge the bulb into boiling hot liquids. Measure the pH of the solution before it is heated or set aside a couple of tablespoons to cool to room temperature after ladeling the rest into jars. With proper care, a pH meter will last for a long time and is a great investment if doing a lot of canning.

        1. Reading about these ph meters is confusing. Is your Hanna one hard to calibrate? I just need it for canning. I assume that your food needs to be room temp?

  • I wanted to offer a little clarification about development of the Botulism spores. The spores are essentially a state of the Clostridium botulinum bacteria that exist as a sort of resting form where they may exist stably for years without growing. When the acidity is insufficient (pH is too high), the Botulism spores can activate and become reproducing C. botulinum bacteria. The growing bacteria produce the botulism toxin and cause the disease Botulism.

    1. Thank you, Hope, I had the shivers every time I read “spore germinates into the botulinum toxin”. You saved me from having to do the explanation myself. Great job.

  • Hi Marisa,
    wonderful site with info beyond what the extension office gives. I really appreciate it.

    I have a question for you about hot sauce. Currently we make it as a fresh product (ie, we bottle it but tell friends to keep it in fridge and consume fast). Our process is to sanitize all equipment & lids, boil the sauce, clean, sanitize, and heat the bottles in oven, then funnel fill the hot bottles with the hot sauce, cap it, turn upside down to heat the lid.

    I’m fine with that process for a fresh product but I’d really like to have something with a long shelf life. But it’s very traditional to use woozy bottles for hot sauce. I think the lids are actually boil-able. Should we consider a hot water boil of the bottles? The “big boys” must be doing something like that or those bottles would not be shelf stable.

    1. Kathryn,
      First the caveat – I am not a commercial manufacturer or a food scientist and I speak only from my own years of experience.
      I make and bottle hot sauce at home – different varieties.
      I used different red chilies that I ferment and age myself with only salt. This can naturally produce a pH of as low as 3.2 (verified by my carefully calibrated pH meter).
      I combine all of my ingredients, bring the sauce to a boil and simmer for 2 minutes.
      I cool a couple of tablespoons and check the pH. I shoot for <4.0 to be very safely below the 4.6 recommended for canning.
      I bottle the sauce just like you do. Clean bottles, heated in the oven to 200F, and I funnel in the sauce (making sure the sauce is at least 180F).
      I leave about 1/2" of head space, and I cap the bottle with a reducer and the plastic cap. I also invert the bottles and allow them to cool this way. I do not refrigerate afterwards.
      I've given away hundreds of bottles that I packed this way with no issues.
      I make a few different varieties and some of them are super-hot with ghost peppers and scorpion peppers, so a little goes a long way. I have had open bottles in the kitchen cabinet (not the fridge) for a year and they still taste great. The color changes a bit from the original due to oxidation, but that is about it.
      I also have bottles that were unopened on the shelf for a year, and when I open them, they are as good as the day I bottled them.
      Again – this is just my experience. It is hard to find good solid info on this online, but not impossible.
      Good Luck!

  • Your website is so awesome! So, thanks for that. Being new to canning, this post got me thinking. I am a huge fan of ginger, and lots of it. I love making applesauce and pear sauce and throwing in a heap of it. But in reading your post, I’m wondering if that’s not such a good idea. All the recipes I’ve seen with ginger in them call pretty small amounts of fresh ginger, or ginger powder. If I go throwing in a couple of big chunks, will I be throwing off the PH? I did use a bunch of lemon juice as well, so I’m hoping it balances out?

    1. If you’re making fairly large batches of apple and pear sauce, it shouldn’t be a problem. Both apples and pears are quite high in acid, so it should be fine.

  • I’m trying to figure out how to make a chocolate sauce that I can safely can with the following ingredients: cocoa powder, rose water, rasperries. Any advice would be much appreciated!

  • Great article! I’ve been canning for a year or so and I’m beginning to sell to friends and family who can’t get enough! I want to create new recipes and need a pH tester. After checking out the FDA link, in theory if I only use high ph level foods without addition, based in treated recipes (for sugar amounts etc) would I even need t test these recipes?

  • Oh you may be able to help me Marisa! I’m new to canning fruit. Usually can and not waterbath. I had a great fig harvest this year. In short I didn’t follow the recipe, I got on another blog. Huge mistake, #1 but here’s my quandary… recipe called for 4 lbs of figs per 4 cups of unsweetened apple juice. I put 24 pounds! (Yes pounds) mistake # 2 in a huge pot and began simmering…but I only had 8 cups of Apple juice. I figured only about 4 more cups would fit anyway (no biggie-I think bad mistake #3) anyway balsamic vinegar, lemon juice, vanilla etc went in the right proportions but as it began bubbling I immediately noted a fermented smell.

    So… is this safe? It has sat in various places, inside on the counter, outside on a table, then back in the fridge. I know… just having a really difficult time throwing that many figs out! After sitting out all night then the next day, the taste has subsided. I refrigerated a small portion that I immediately got out and blended. It was my taste test batch that tasted horribly like a cheap wine. That batch has been in my fridge and now after 3 days, tastes almost normal with very little ferment taste. What and how is this? So what should I do. Please help and thanks in advance.

    1. Naomi, I just can’t tell you whether something is safe or not. You need to determine whether it’s going to be something you want to eat or not.

  • Thank you Marisa, for this blog. The best info i’ve found regarding this new kitchen world for me.

    You mention, “We’ll talk more about how to preserve those foods that are low in acid and have a pH of 4.7 or above another day,..”

    Any chance that day will come? Or has it come and gone without my noticing?

  • Thank you again for explaining science behind the process!!

    I’ve thus far avoided peach jam because I don’t feel like peeling a boatload of peaches. **shrugs** I know you have a “Lazy Peach Jam” so maybe I ought to give it a try anyway with peels on :).

    I bought 2.5 pounds of yellow nectarines yesterday, planning to make a small batch of stonefruit jam that does NOT require peeling! As long as I follow a trusted source’s recipe for peach or apricot jam, ensuring I add some bottled lemon (lime) juice along the way, it sounds like I’m safe. But I’m really really curious — how come I can’t seem to find any trustworthy nectarine jam recipes out there? Strangely, the National Center for Home Food Preservation only lists a preserve (whole fruit + syrup), no jam. I forgot to look it up in my Ball Blue Book — but I’ve yet to follow a recipe from there because it always calls for TOO MUCH SUGAR.

    Side note: My grandma used to can the peach peelings separately and then make handpies with them. They were probably my favorite preserved fruit of hers. Something about the peachy flavor and the texture — I have never had anything since that even came close. Okay, they were a strange brownish color (oxidation I presume), but amazing.

  • My husband added chicken bouillon to the tomato sauce I was going to can in a water bath.
    Is that acceptable?

  • The rules have changed! If you do high acid canning, the FDA has new rules for testing ph. I just had my inspection today. I sell canned goods and now anything with a 4.0 ph has to be batch tested at least 4 times per year with ph test papers or a ph meter. Anything above 4.0 to 4.6 needs to be per batch tested with a ph meter. Mind you, this is after initial testing at a certified lab. You must have standardized recipes and have HACCP plans for your recipes. Oh, and you need to have a log book, your canned goods must be labeled, and have batch codes (I am a home processor.)

  • Getting ready to test the Ph on this sauce to see if it can be canned: 1/3c honey, 3 TB minced chipotle chiles in adobo, 3 TB balsamic vinegar, 2 TB dijon mustard, 1/2 c fresh lime juice, 1 1/2 TB minced garlic, 1 tsp allspice, 1/4 c chopped cilantro, 1 tsp kosher salt, black pepper…if the levels are ok for the ph, I was going to pressure can this but was unsure of the pressure and times. Using half pint jars at 4700′ elevation. Any thoughts?

    1. Karen, I really can’t advise on developing pressure canning times for an untested sauce. If the pH is below 4.6, you should actually be able to process it in a boiling water bath canner.

  • Hi. I have a question for you in the use of honey as a sweetener. I’ve been canning for a few years. (only high acid foods, really. I have a pressure canner, but it still freaks me out.)

    I recently realized that I had no idea how canning with honey as a substitute sweetner was ok. I know botulism spores can be present in honey. Is it ok because the pH of the food prevents it from reproducing? And if that is the case, why isn’t it possible for a small amount of honey to be sitting on the top of the canned food, near the headspace and not be inhibited by the pH?

    Am I overthinking this?

    Thanks to anyone who can answer.

    1. It is possible for the botulism spores to be present in honey. However, like you said, as long as the pH of the total product is below 4.6, it is not possible for those spores to germinate into the toxic form. And once you’ve boiled honey into a preserve, there’s no practical way for it to separate out of the finished preserve. So on the whole, it’s really not something to worry about.

  • Hello Marisa, I have your book preserving by the pint. Today i followed you recipe for Blender Salsa. I canned 3 pints but forgot to put in the 2 tablespoons of bottled lime juice. I’m kind of new to this and i was wondering if this small batch will be okay. I used the water bath method.

    1. The lime juice in that recipe is vital for safety. You need either open the jars, add the lime juice, and recan or store that salsa in the fridge.

  • Hello, I have a question. When trying to acidify foods, how do you know how much acid to put in? If I wanted to use a powdered citric acid or lemon juice how do you determine how much is enough? Thanks Marisa love your blog!

    1. It depends on what you’re trying to acidify. If you’re working with tomatoes or fruit with a similar pH (they tend to be between 4.3 and 5.0, but we always treat them as if their pH is higher than 4.6), you use 1 tablespoon lemon juice or 1/4 teaspoon citric acid for every pint of product. Unfortunately, there’s no reliable formula for anything with a higher pH. Beyond that, you need to be testing pH or pressure canning.

      1. Marissa, when you say add 1 tablespoon of lemon juice per every pint of product. Do you put the lemon juice in recipe? or directly into jar? I put mine in the recipe. Is my salsa okay? I used a boiling water canner bath. Thank you.

        1. Typically in batches of salsa, the lemon juice is added to the recipe. When you’re packing plain tomatoes, it is added to the individual jars.

  • I have no idea if you’re still checking the comments on this, but in case you are… I’ve never canned before (I’m 22), but I have some blood oranges and Meyer lemons that I’d like to make marmalade out of. The recipe I’m planning on using, which is for blood orange marmalade, calls for 1 pound of blood oranges and 2.5 cups sugar, and I’m just planning on substituting a couple lemons for a couple of the oranges. Botulism is a bit terrifying to me (understandably, I think), so I was wondering – should I get something to test the pH before canning, or am I safe canning citrus using a water bath? I’m not planning to put anything else in the marmalade other than the oranges/lemons and sugar. Thanks!

    1. You are totally safe changing that recipe because citrus is uniformly acidic enough to prevent any kind of botulism.

  • I’ve been dreaming of a beet jam, made in the slow cooker like your fruit butters, acidified with lemon juice and balsamic vinegar, sweetened with honey, and water bath canned. Around what percentage of it should be lemon juice and vinegar for safety, do you think? I know that beets are not very acidic according to the PH chart.

    1. There’s a recipe in my new book, Naturally Sweet Food in Jars, that has a recipe for beet ketchup that you might be able to use as a starting point. It’s pretty acidic, though.

  • Hi there. Very much enjoying reading all of your information.

    I have a tomato recipe that I’ve made for decades. My grandmother made it for decades before me. (Its basically 5 quarts tomatoes soaked overnight in white vinegar, drained in the morning, two cups of vinegar re-added along with 6 cups of sugar with a spice bag (allspice, cayenne, cinnamon) and then boiled down over about two hours or until thick.) Think tomato jam.

    I have always used paraffin because my grandmother did, but know that it is not recommended and I do understand why. This is the only recipe that I’ve used the paraffin with, nevertheless, I am nervous about doing it without the wax. Am I correct in assuming that if I can add enough extra vinegar, or lemon juice, or combination of those so that I can get the ph down to 4 that I can go ahead and process it the canner?

    I checked with a food scientist and they seemed to feel that in this case the texture would be destroyed in a pressure canner.

    My grandmother lived to be 107 and this recipe is a bit of an heirloom which I’m hoping can be maintained. We are oddly and emotionally attached to it, as strange as that may sound.

    Any information would be very greatly appreciated.

    1. With that much vinegar, I am certain it will do just fine in a boiling water bath canner without any alternations. However, if you’re at all nervous, the protocol for acidifying tomatoes is to add 1/4 teaspoon per pint of product to each individual jar prior to canning.

      1. Marisa, I just wanted to drop back in and thank you for all the wonderful advice you have on your site. You were entirely correct about the amount of vinegar in my recipe. I actually purchased a ph meter and tested the batch I made two weeks ago, as well as a jar from last year. I’m embarrassed to admit that while digging around in my pantry I happened upon a stray jar that was dated 2011! No worries, I don’t keep things that long! (Every jar is marked with the date and a batch number and discarded as needed but somehow this one jar got left behind). If nothing else, that added a bit of interest to my science experiment! All three jars tested with a ph of below 3.94! So looks like I’ll be back to the chili sauce making with jars to give away at Christmas as always (only this time with the canner boiling and without that terrible paraffin). Once again, many thanks!

          1. Okay…I lied…I’m back. Marisa, correct me if I’m wrong but I think you have two different tomato jam recipes on your site? One you had left 1/4 inch headspace and the other 1/2 inch. I’m not sure which would be best in my recipe. It is quite thick….more a jam texture than a salsa texture. Thoughts? Thanks again!

  • Love your blog and recently purchased your book “Preserving by the Pint: Quick Seasonal Canning for Small Spaces.” I hope this thread is still actively monitored, as I have a question regarding acetic acid.

    If I have a canning recipe (water bath) that would normally call for vinegar, may I substitute an acetic acid solution that is equal in acidity to the vinegar? An article on Pomona’s site indicates I can create a 5% acetic solution by combining 2 tablespoons of fine acetic acid powder with 2 cups of boiled, cooled water. If I used this solution to can some peppers, would they taste less “vinegary” than if I canned them in vinegar? Would that vinegar flavor profile still be there with the acetic acid?

    What I am trying to do is can roasted peppers that don’t taste pickled without using a pressure canner.

    Thanks for any direction.

    1. Nancy, I am so sorry, but this question is a little bit outside my comfort zone. I really can’t advice you here. My apologies.

  • I canned two different sauses. The recipes called for vinegar in both. I boiled half pint jars for 15 min. After reading about tomatoes, I wonder if it’s ok? Your in put would be much appreciated. Thanks

  • Hi there! Wondering if you could send me the link to the FDA list of produce with ph levels? The link above is broken and I’m having a hard time finding it on their website. Thanks!

  • Marisa, I made your peach salsa with nectarines and Shiro plums in place of peaches and with twice the number of jalapeños. Delicious, and I’d like to make some more, but now I wonder if I might have altered the pH too much.

    1. That’s shouldn’t cause too much issue with the pH, unless the jalapenos were quite enormous. Next time you make such an adjustment, consider upping the acid a little, just to be safe.

  • A very complicated question from an obvious amateur without the proper equipment :
    Given (if true): My understanding of C. Botulinum is that the destruction of the spores can cause a release of the toxin. So, if there are the conditions where the active bacteria multiplies and then they are “under-cooked”, so that they turn to spores (as a defensive measure) – if they are cooked again resulting in the destruction of the spore but not the denaturing of the toxin (i.e. boiled, but not under pressure) this could result in higher risk of botulism.
    Scenario: I have baked pumpkin shells (low acid) at 350 deg for and hour – mashed and then refrigerated (not necessarily below 40 deg as it took hours to cool). 4 days later (around the room temp incubation threshold) I reheated (slowly) added lime juice (most likely not enough to lower pH) then did a boiling bath method – then returned to refrigerator (not shelf).
    The Question – if, within the next month, I use this in baked goods cooked at roughly 350 for an hour… would this be safe?

    1. Keep the canned pumpkin in the fridge is probably what’s keeping it safe. In order to germinate, botulism spores need an environment that is low in acid, oxygen-free, and at room temperature in order to germinate. You created all three of these conditions when you processed the pumpkin in a boiling water bath canner. Even with the pumpkin in the fridge, there is a risk. I would discard this pumpkin, and in the future it would be better to skip the boiling water bath process and simply freeze the finished puree.

      1. Thank You. That’s kind of what I was suspecting. I just didn’t know, considering all the half-measures (the sugar, salt, lime juice and boiling it before the waterbath and refrigeration immediately after) – if it was able to be salvaged considering the time and ingredients… I just did the bath and refrigeration yesterday – do you think that it would be safe if I cooked with it by this weekend? And does baking it afterward achieve the needed denaturing of the toxin?

  • FOLLOW UP to complicated newbie question… I also added coconut oil (not sure if this is an inhibitor as it is with other things), sugar (probably not enough for inhibition in and of itself), salt (same) and spices to the blend. I understand what SHOULD be done. I do not have pressure cooker and/or canner, I have a pumpkin patch, and I do not plan on storing anything at any temperature above that of a common refrigerator – even as such, not for longer than a month.

  • Hello, I made salsa yesterday using a mix from the canning section that has been tested (it states). It called for 10 cups cut up tomatoes. My tomatoes only yielded 6cups, so I added 2 cups of fresh peaches to the mix along with apple cider vinegar and lemon juice as it called for. Then after cooking for time stated,I added some pear relish I had made day before (canned). Then Ladeled it in Jars and did hot water bath for 20 minutes. Did I make a mistake by adding Different than recipe called for(fresh peaches and pear relish).

    1. I really can’t speak to the safety of this recipe since you’ve made so many changes to it. Adding the peaches would probably have been okay, but also adding the pear relish brings too many variables into the mix.

  • I’m concerned about the safety of a recipe I just made. I know bananas are low acid, but they are mixed with pineapple and lemon juice in the recipe. Does that raise the acid level enough to make this recipe safe to water bath?

    1. I can’t determine whether a recipe is safe or not based on a short list of ingredients. If you doubt the safety, you can refrigerate the jars rather than keep them on the shelf.

  • Can you test the ph of salsa when you open a jar to use it? If it is added to a chili recipe and cooked/boiled for at least 10-15 minutes will that kill botulism if present?

    1. It is thought that a 20 minute hard boil will kill any botulism spores present. But it’s still not a good idea to can untested salsa recipes.

  • I’ve canned for years. But have never attempted meats. I do have a pressure canner. I recently made a small batch 2.5 cups of jalapeno onion bacon jam. It has .25 cup of balsamic in it. Bacon cured then fried..any reason this couldn’t be hit bathed?

    1. I don’t know of any bacon jam recipes that are safe for processing, in either a water bath or a pressure canner.

  • I’ve been looking at a corn cob jelly recipe and wondering if it’s safe to can with a water bath. Even though corn is slightly acidic, I can’t see it being acid enough even though everywhere I’ve seen it, they say it’s fine. I’m thinking of adding lemon, but how do I calculate how much is enough?

  • How many tablespoons of vinegar would I need to add to a pint of bean and spinach soup so I can can in a water bath?

    1. There is no way to safely do what you are suggesting. The only safe way to can soup is in a pressure canner.

  • I have a recipe for caning zucchini in pineapple juice, it calls for 3 cups added sugar, I’m wondering if it’s okay to eliminate all of it or what if I exchanged it with monk fruit?
    There are also several recipes to make apple pie filling with zucchini, and I’d like to use a sugar substitute and am wondering if that’s safe?

  • Hi! Sue here! Just read all of this post. Great! But I’m canning drilled green tomatoes, using just a pot & rack. My question is, the other one I read said just 1-2” of water in the canning pot, yours says filled to the top without exposing. Is yours filled over the top just for jams or can I follow your instructions for this pot for filled items as opposed to jelly’s or jams. Thanks! Hope you see this before tomorrow! LOL!

    1. Any time you process something in a boiling water bath canner, the jars need to be fully submerged and have enough water over the top that the jars won’t boil to exposure during the processing time.

  • I am very new to canning and have received conflicted advice concerning pickled beets. Keeping all ingredients the same: beets, sugar, vinegar most sources say 40 minutes in a water bath canner (at 3,100 ft). However a long time friend says they only need 10 minutes because of the high acidity – if it were low acid in a pressure canner it would require 40 minutes, according to her. Can you bring any clarification to this issue? Does the amount of acidity change the time required?

    1. Pickled beet processing time recommendations have changed a bit over the last few years. The National Center for Home Food Preservation now recommends 40 minutes of processing in a boiling water bath canner at your elevation. If you were to do them without acid, you would need a pressure canner and the processing time would be 30 minutes for pints and 35 minutes for quarts, at 15 pounds of pressure at your elevation.

  • Greetings! I am interested in making a mulberry jam that can be stored long term. I do not want to add any sugar and was thinking of using a little cornstarch as a thickener. I make pancake syrup this way with the mulberries and it preserves the natural taste of the berries the best way. But with the cornstarch, can I still water bath or should I use a pressure canner? I am concerned the corn starch may change the way the temperature of the water penetrates the jars. Could I just boil them longer? say 10 or 15 minutes? I found plenty of recipes using corn starch to thicken, but only for use within a few weeks and not canning for long term storage. Can find no information other than that the corn starch will change things, but no information on what to actually DO to keep it safe. Any help or suggestions?

    1. I don’t recommend doing what you’ve suggested. Cornstarch is not a shelf stable thickener and so the mulberries might end up runny again over time. It also causes density issues, like you suggested. If you want a sugar-free mulberry preserve, I recommend you cook and can the berries without any thickener and then thicken with a little cornstarch once you open the jars.

  • Have a question if when you open a jar of home canned tomatoes canned in their own juice if you test the ph and it is 4.5 or lower does that mean that the jar is safe from botulism growth?