I hate making yeast starters. I want to make 5 gallons of wort and fill up a bunch of mason jars, and use these mason jars to make my yeast starters in the future. I also want to store the mason jars at room temperature.

I was thinking of heating a solution of star san to 140F and filling the mason jars with this solution. I would cool down the wort to around 140F before filling the mason jars. The reason for this of course is to prevent the non-pyrex mason jars from breaking due to the extreme change in temperatures. I would cap the mason jars and store them at room temperature.

Question: will this procedure work? I am making several assumptions; for example: star san at 140F sanitizes properly, wort at 140F can't become contaminated, and the mason jar seal is air tight and won't result in an infection at room temperature.

  • 1
    This sounds like a botulism risk. Your wort is only fairly acidic and has lots of sugar so even a few cells of something like botulism will grow and can be deadly. Freezing is a common option if you don't have a pressure canner.
    – chris vdp
    May 12, 2016 at 17:58

4 Answers 4


Without pressure canning, unfermented wort doesn't have a low enough pH to be shelf stable.

From The Maltose Falcons website:

The process is almost identical to the one that you or your family may have used to preserve peaches, tomatoes, pickles, etc. The normal preservation method is hot water bath canning, but since wort is a low acid food you must use the more intense method of pressure canning (per the FDA). So to safely can your wort, you'll need DME (or wort), some yeast nutrient, a pressure cooker and a case or two of Quart (or pint) Mason Jars.

  • Would you please explain what you mean by shelf stable - what exactly would happen to unfermented wort that was not pressure canned? May 11, 2016 at 6:10
  • 3
    The term shelf stable is what you are asking for. It means a jar of put up food product will last on.the.shelf. (i.e. room temperature) Meaning microbial contamination does not lead to further growth of the microbe while on the shelf.
    – brewchez
    May 11, 2016 at 10:21

Sanitation is not sterilization. You might find a couple jars out of a batch last longer than others. But the only way to be sure is to buy a pressure canner. They are relatively cheap and can be used in the kitchen later for cooking as well. Mason jars make great containers, but lets not lose site of what they are really made for... sterile canning. In fact, one of your assumptions is the lid sealing properly. Simply screwing on the top of a two piece mason jar lid (the disk and the ring) does not make a "proper" seal as designed. Its the cooling effect post the high heat that creates a vacuum and sucks a loose lid down tight and makes the true seal.

That's the option here, unless you want to purchase a small countertop autoclave.

Wort that is not sterile may eventually start to grow stuff. Could be as simple as innocuous mold, yeast or bacteria. But you could also start growing something that would make you ill, like Clostridium botulinum. The spores can only be destroyed through high heat. Star-san doesn't touch it effectively. And it doesn't have to grow much. Even if it just gets started in a jar of unfermented wort, it will propagate more once you make your starter and you may not notice.


Yeah, unless you actually pressure seal those bad boys, I wouldn't risk it. My rule of thumb is to weigh out the possible benefits and down falls of taking a shortcut. The upside could be saving a few minutes of heating then an hour of two (where you don't have to be around or do anything) waiting for it to cool. The down side is very high - at best, you could open your first and find all those cans have spoiled, or perhaps you don't notice until you pitch the starter, then all of your hours and dollars you put in to brew the batch as well as the pilot starter batch is gone. Worst case, that happens and some one gets sick.

If you want to bottle a liter at a time and keep those in the fridge that would absolutely be the best solution, though you still will have to wait for it to warm up - much like waiting for it to cool. So, in the end, it's kinda a wash - with more factors and infection points added in on one end. I'd say flush the idea.

Now, if you want to do a hybrid where you precook and refridgerate half a liter to add to another half liter of starter you boil fresh to help bring the temp down faster and sanitize the pre cooked portion, have at. That or make a 2x concentrated starter that you half with boiling water to give a quick temp flash to kill anything in it and speed up the cooling as well. Both make sense to me.



It's much simpler to use 1/2 gallon or gallon plastic juice bottles. Freeze or refridgerate the boiled wort.

When using I bring my starter flask of wort to boil for a few minutes, chill and inoculate.

I get that mason jars at cellar temps would save fridge space, but if you use larger bottles keeping a couple gallons of wort in the back of the fridge/freezer isn't too bad.

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