You have died of dysentery. Or botulism.
August 5, 2016 11:16 AM   Subscribe

I'm a home canner with a glut of watermelon, a love of lemonade, and a strong desire to not die of a preventable poisoning. In theory, is it possible to pressure can a watermelon-lemonade/limeade concentrate without creating the perfect environment for botulism?

I understand that melons are a 'no-no' when it comes to traditional canning; they are a very low-acid food and their texture suffers from the time/temps required to kill botulism spores in a home pressure canner. Thus, there are no tested recipes for home canners. Dr. Google, PhD, only provides one dissertation from the 1940s examining the quality of commercially canned watermelon juice. There are a plethora of home-canned lemon juice recipes, however, and Oregon State University gives instructions for safely canning higher-acid fruit juices. There are numerous recipes for preserving low-acid jellies and vegetables, including watermelon jelly, which are made safe by the addition of a sufficient quantity of acid (lemon juice, vinegar, etc.) to reduce the pH of the recipe below 4.6, the level that botulism spores are no longer active. (Though I understand there was a series of botulism poisonings a few years ago from a commercially-sold watermelon jelly.)

So, quality and taste considerations aside... If one was to combine strained watermelon juice with enough lemon or lime juice to produce a concentrate with a pH of at least 4.5 (and ideally even lower to provide a safety buffer), carefully test/confirm that pH, and then process in a boiling water bath or pressure canner like similar low-acid fruit juice recipes, would the resulting jars be likely to encourage botulism spore growth? Or would the acid levels be high enough prevent development? Are there other factors or issues that have kept researchers from testing melon-based canning recipes?

I have a quarter-acre of very productive watermelon vines and I've already explored watermelon wine, dehydrated watermelon slices, frozen watermelon custard, frozen watermelon juice, watermelon jelly, watermelon pickles, and food pantry donations. Even my chickens are getting tired of them. The idea of being able to put up juice for future enjoyment (without having to buy a watermelon-dedicated deep freeze) really appeals to my family, but only if we aren't playing fast & loose with our health.
posted by muirne81 to Food & Drink (10 answers total) 2 users marked this as a favorite
 
Here's a how-to for canning juice concentrate from Southern Kitchen. I don't see why you couldn't adapt her technique for your watermelon! Strawberry-Lemonade Concentrate
posted by jhope71 at 11:29 AM on August 5, 2016 [1 favorite]


So, quality and taste considerations aside... If one was to combine strained watermelon juice with enough lemon or lime juice to produce a concentrate with a pH of at least 4.5 (and ideally even lower to provide a safety buffer), carefully test/confirm that pH, and then process in a boiling water bath or pressure canner like similar low-acid fruit juice recipes, would the resulting jars be likely to encourage botulism spore growth? Or would the acid levels be high enough prevent development? Are there other factors or issues that have kept researchers from testing melon-based canning recipes?

My understanding is that everything that you said in the preceding paragraph is correct. There is one other thing that is done when developing canning recipes, which is to measure pH over time in case there is some kind of reaction that occurs to raise the pH above safe levels. I don't have any intuition how this could occur in your case, though. Low-pH juice seems pretty safe to me.
posted by quaking fajita at 11:31 AM on August 5, 2016 [1 favorite]


I was thinking about watermelon simple syrup but I wonder if this recipe for long-cooked syrup (to put on pancakes, etc.) would be any safer? In any case, it reduces to 1/7th of its original volume, so it should use up a lot of fruit. The recipe also says you can "cook the sap all the way down to a cake that tastes even better than maple candy."
posted by beyond_pink at 11:34 AM on August 5, 2016 [2 favorites]


If you make the concentrate and freeze it in appropriate amounts, not only will you not have to worry about botulism, it'll already be cold when you want to make some.
posted by fiercecupcake at 12:28 PM on August 5, 2016 [9 favorites]


If you have the technology to pressure can, I don't even see why you would need to concern yourself with pH so much--as you seem to be aware, pressure canning is precisely the technique used to safely can all sorts of things that are not high acid. With enough sugar and acid to create watermelon lemonade concentrate, pressure canning is probably overkill, so to speak, but if you're worried about it being an untested recipe, that's certainly what I'd suggest.
posted by drlith at 2:08 PM on August 5, 2016 [3 favorites]


This is TOTALLY relevant to my interests!

Pressure canning is a totally different game from water bath canning, and what is impossible with water bath methods is suddenly possible with pressure, so you may need to not worry so much if you can find a tested pressure method for a melon product.

Preserving watermelons and melons in general:
According to this extension office, there is no safe watermelon preservation outside of drying or pickling. (Pickled watermelon rind is DELICIOUS, though.) This PDF describes a water-bath recipe for cantaloupe-peach preserves which they've tested for safety, but they indicate that no pressure-canning testing has been done on melons because of texture problems with a finished product, and they say that dehydrating is not advised. I guess preserving melons is poorly researched. This PDF is a no-sugar added, tested by an Extension Office, cantaloupe pickle recipe. Cantaloupes are actually a little higher pH than watermelons, so if you search for cantaloupe preservation, that might help broaden the search.

Preserving a syrup made of watermelons:
You could also look into cooking it down into a fruit syrup and preserving the syrup. This PDF and this PDF describe a water-bath canning method for fruit syrups, but they are both suggesting berries or grapes as the fruit, which are both high in acid. This PDF tells how to hot-pack maple syrup (which has the same or higher pH as watermelon), but I am giving it to you without a lot of trust because despite being an Extension Office, they're suggesting an inversion method, which is known to be less safe as a method in general. This Clemson Extension link and this National Center for Food Preservation link about preserving fruit syrups is pretty promising, but those are all pretty acidic fruits. And of course, I can't find anything about pressure-canning fruit syrup (I guess people figure that if water-bath is good enough, they don't want to deal with pressure, so they don't research it.) Obviously there is a way to long-term preserve maple syrup, simple syrup, grenadine, etc. since I've bought them commercially-- and I'm assuming it's a pressure method, potentially with chemical preservatives. But I don't know how you'd do that at home.

Strawberries are much more acidic than watermelons, so the recipe posted for strawberry-lemonade concentrate above might not be safe as a direct substitute with watermelon. I would think that a one-to-one mix with bottled commercial lemon juice would be OK, but I might also be wrong. In this instance I would make that long-cooked syrup and use it as a sweetener in a lemonade concentrate recipe that uses maple syrup or another sugar syrup. I'd also consider looking into pressure-canning times and ratios for melons and melon juices, if any exist, or any low-acid juice processing, of which I can't find any. I think a pressure-canning recipe for a low-acid juice that is sourced from an Extension Office is your gold standard for safety here, and I don't know if that's a thing.

You could also call your local Extension Office. If yours is not helpful, try calling a couple counties over.
posted by blnkfrnk at 2:26 PM on August 5, 2016 [3 favorites]


What about a watermelon margarita mix? OMG.

Ditto posters above. With enough sugar and acid, anything is safe.
posted by domo at 2:27 PM on August 5, 2016 [1 favorite]


Master Food Preserver here, I made an account just to answer this question. I'm making cantaloupe jam RIGHT NOW and it's delicious. If you're worried about it being grainy or the texture suffering, you can always run it through a strainer. That's what I do anyway. I wouldn't make juice. I have gone through my multitude of books and haven't found a recipe. Watermelon is WAY closer to neutral than tomatoes. Testing the pH sounds good, but unfortunately over time pH can change as it's sitting on the shelf. As for pressure canning, I wouldn't do that either. Even if you're free of botulism, the jam can still go off (ask me how I know!). There are lots of other foodborne illnesses. Without being tested in a lab, you just can't know for sure. If you like the idea of drinking the juice, maybe make a jam and add sparkling water. I'm sorry I couldn't give you better news. Ball has some great melon recipes in their books though, so I'm sure you can find something to make you happy. Good luck! Too much watermelon is a great problem to have.
posted by Bistyfrass at 4:04 PM on August 5, 2016 [9 favorites]


I am terribly sorry that I have no actual solution to your problem except for you to have a MeFite watermelon party. I promise that I could single-handedly put a big dent in your watermelon supply, and I bet I'm not the only one. Good luck!
posted by Bella Donna at 5:01 PM on August 5, 2016 [4 favorites]


Thanks for the wonderful answers & comprehensive research assistance, MeFites!

After taking in all of your advice & asking the local university ag/chem folks as well, we're going to forge ahead with the watermelon-lime/lemon juices & syrups -- making sure to test the pH pre-canning and pre-consumption. (We do have a very accurate pH meter, which helps.) We're also researching indy testing services to see if we could confirm safety after, say, 6 months of shelf storage. Yay for microbiology!

A few of you commented about freezing -- as much as we'd like to be able to just freeze the juice and be done with it, we have already filled two extra-large deep freezes and a stand-alone fridge with various foodstuff from the farm... It's getting a little ridiculous around here. (A barn cooler is at the top of my Christmas list!) But necessity is the mother of invention, as they say - if/when we get results back I'll check in for all of you fellow watermelon fans. Perhaps I need to write a melon-only cookbook!

Thanks again, virtual watermelons for everyone!
posted by muirne81 at 1:52 PM on August 8, 2016 [3 favorites]


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