Last sunday we brewed a couple of black porter batches with my buddies and we used a generous amount of roasted barley with pilsen malt. We put it into the frigde as soon as we finished mashing, as we did the brewday before.

I have arranged with a local bakery to give them my spent grain for them to bake over a few days. The problem is that last time our spent grain smelled nice all the time (Amber with caramel malt, pilsen and a bit of brown malt) but now it has a funky smell all over it (brown, chocolate malt, roasted barley and pilsen). Today, when I opened the bag to inspect it, it smelled alright but when you pry it arount the funky smell comes up.

I made some malt cake a cuple days ago and it was alright. I'm afraid to deliver this spent grain now because of the smell. I tested a little sample in the oven and I kindof hint the smell comes from some natural compound in the roasted barley, but that's just a hunch.

I will test it tomorrow morning by baking malt cake again and see if it tastes good, or whatever.

Any idea why it smells weird this time?

  • Whats the time gap between the mashing and the usage of the spent grain? Even in a fridge, I don't think spent grain would be good for anything other than whole-grain sourdough dog biscuits after a day or two. There's just too much microbial activity going on. I've seen grain piles left outside turn nasty within a matter of hours.
    – GHP
    Oct 4, 2013 at 13:49
  • I used a bit of the spent grain to make my cake test and it came out just fine, I think some of the smell character in the roasted barley makes it smell kinda weird. I then went to the bakery and asked them about the batch I dropped a month earlier and they told me it was still going just fine, no funky smells or anything and indeed they had spent it all during those 4 weeks in experiemnts and tests that worked just perfectly. SO I'm not in fear anymore. Oct 5, 2013 at 19:19
  • We first used it experimentally, applying spent grains from our new local brewery to Municipal flower beds. Wow! Okay, we didn't really know what we were doing. The idea seemed to make sense and have merit. We should have dug it deep into the beds, not laid it on top, in July heat. Worst of all, some of the beds were at the Police Station in the middle of downtown! Nothing smells better when it comes fresh from the tanks, but by the next day. Yeah, BAD! So bad in fact, we had to talk our way out of a citation for fouling the air. Major lesson learned. We made a special area for the grain to co
    – Fran Rohm
    Jan 11, 2023 at 22:26

1 Answer 1


Spent grain goes bad fast, and when it goes bad, it's bad. And not a little bad. bad.

not even bad in fact.


I've used spent grains in compost for a long time and if you don't mix it in while it's still hot (or if you're unlucky enough to leave it sitting for a few hours or - god forbid - days) you will face a soul-crushing, stomach-lurching, ramped-up-bile-producing foulness the likes of which you'll never hope to encounter again.

That said, it's great for making bread with :p However you need to follow some basic protocols. here's a good guide. The most important thing is squeezing out the liquid, and if possible, spreading it out on a clean tarp or something so it dries/cools quickly before you throw it in the freezer (freezer, NOT fridge). Think about it - hot, wet, full of pre-processed sugar...what better environment could there be for bacteria? If you're brewing on a large scale (or just have a lot of grain), dip out a few scoops to save for making bread with (alternately you can use it to make sponge for bread while it's still warm, but since you're not actually making the bread you won't want to do this) and use the rest for compost.

  • Thank syou so much for your tips, I will practice some better practices next time, As I mentioned in my comment above, I tried baking my home test cake and it was all fine, so I'm thinking the roasted barley adds some funky smell all by itself that I just wasn't expecting. I kept about a kilogram just to sample it every few days and if it starts smelling to bad I will call the bakers so they thow out the grain I gave them. Oct 5, 2013 at 19:21

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