Unboiled wort question

This past Sunday was a brewday for me. I ended up with a little less than 1 gallon of 2nd runnings from my sparge leftover.

I decided to save it for making starters. I have not tested gravity on it yet so I have a couple questions.

First, how long will it keep in the fridge?

Should I have boiled it then saved?

If the SG is say less than 1.030, how to I calc the amount of dme to bring it up to say 1.035 or 1.040?


Boil it down to 1.035 (boil for at least 15 minutes) and use immediately for the starter, then save the yeast cake if you can’t use it now. Or pressure cook the wort for long-term storage.

Or freeze it and boil before using.

You need to boil it to preserve. Otherwise it will begin to spontaneously ferment within a couple of days.

Don’t worry about the specific gravity. It will be fine for a yeast starter. But you do want to boil it right away so it doesn’t ferment via wild bugs. I’ve done this before. If boiled for a few minutes and placed into a well sanitized jug and kept in the refrigerator or freezer, it can keep for as long as a couple of months, although you do still want to keep an eye on it, as the wild bugs will still eventually find it and ferment it, even at ~33 F. Then when you are ready to use it, it is a good idea to boil it again for a few minutes to ensure any wild beasts are gone.

Unless he freezes it, right? Not doubting you Dave, but I want to know if I’m correct.

You are correct, of course. Freeze and then boil is a good alternative. Ain’t much that can grow below 32 F as far as I know, and if it’s boiled later…

Thanks for the confirmation!

There are a few nasties, albiet extremely rare in beer, that can survive below 32F. I know that E. coli and L. monocytogenes can survive in wort conditions (pH) and below freezing for up to 30 days. I seem to remember a study sometime in the last few years that proved that L. monocytogenes can’t thrive in the presence of hops, but the lower the temperature of storage the more prolonged the pathogen life.

For a food product to be certified as pathogen free, it has to be frozen for 20 days or 30 days at 5F, depending on the thickness.


If boiled, it should store in the fridge the same as any food product. I don’t think I would use if if older than 5-6 days.

Frozen, going out a month or so.

Thanks all!

to be on the safe side, I’ll dump this stuff since it sat open on my counter for a couple hours before I remembered I hadnt put it in the fridge…and I wont be brewing this weekend.

All this learning stuff is hard to remember!!!

I have had success going up to two weeks going straight from final runnings to quart jars in the fridge. The wort is usually less than 1.035 so I boil and add a little DME to get to the proper gravity. And I boil for 15 minutes or so as an extra precaution.

I have only had one quart show signs of anything strange growing, so I pitched it. I always smell before using to see if anything seems off.

With a 15 minute boil, what are my risks? I am only making a starter…