The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Ammonia smell in flour?

Urchina's picture

Ammonia smell in flour?

An odd question: The large plastic-ware container that I use for storing unbleached AP flour holds about 6 pounds of flour. I empty it completely and run it through the dishwasher twice a year or so, so I'm always fairly certain that there's no flour in it more than six months old. And I've stored the same bin in the same place for the last ten years, so no new variables have been introduced in storage. 

This week as I was doing some baking, I noticed that the flour in the container smelled of -- well, sort of like ammonia. Wierd. I was getting down toward the bottom of the bin, so this was probably some of the older stuff -- but I've never had this happen before. I dumped the flour out and am washing the bin out tomorrow -- but does anyone have any ideas about how or why this might have happened? No clear source of contamination, all the flour was dry and free-flowing when I dumped it. I'd love to know what might have caused this. 

dwcoleman's picture

Are you confusing the smell of bleached flour with ammonia possibly?  I store my flour in similar containers and haven't had that issue. 

Also white flour usually has an extended shelf life of up to 2 years, 1 year for whole wheat.


Mini Oven's picture
Mini Oven

and rinse the container well with water after it comes out of the machine.  I like to let plastic items dry exposed to the air 24 hours before stacking, storing or using them.  

clazar123's picture

Could this be a self-rising flour? Could there be some baking powder in it? Mislabeled package? Time for a science experiment! If you have some flour left, put it in a bowl and add a teaspoon of vinegar. If it fizzes or bubbles, there is baking powder in the flour.

Just a really wild thought. Otherwise I concur with MiniOven.

Yerffej's picture

What brand of flour was in the bin?

Mini Oven's picture
Mini Oven

The first thing that pops into my head is... where did it come from?  Ammonia is organic, most often produced from urea found in urine.  Most often a sign of mice or cats or fertilizer or lack of toilet facilities.  Lots of ideas pop into my head from the stacked sacks in a warehouse to the cat that marks (sprays) the truck, sack, or bin standing in its territory to the mice in the grain bin/warehouse to the grain being bagged in used fertilizer bags to the workers cleaning out the ship's cargo hold.  All kinds of ways for organic compounds (pee) to get near grain or flour.  Even thought about heavy fertilizing of a nearby field (wind) or flooding from pasture land.  

I would mention it to the store where you bought the flour and to the company (mill) that bagged the flour.  Even better if you still have the batch numbers or the original bag.  I tend to hang on to the original bag until it is used up or write down the info if purchased in a bulk bin.  If a bag is bad, it is easier to return and trace in the original bag than if the flour was transferred to a second container.

I would insist on purchasing a different batch number if replacing with the same brand flour.   

EvaB's picture

and other various donaters of pee! But I also had the thought about HOW OLD IS THE CONTAINER, because plastic will break down over the years, and can give off weird smells and do strange things. Especially plastics that are more than 5 years old, they changed the formulas as well, they do that regularly as soon as we find out there is something bad in the plastic formula (BPA) (lead acetate) and if you didn't hear about the change or the fuss over something your container might still be that forulation and simply be offgassing the  amonia from the plastic due to deterioration.

This is why I use a metal can! (huge Hills brother's tin from a resturatunt) Or leave in the paper bag. I do have smaller bins on the counter that are plastic, but since they are newer plastics they tend to break down faster so they get recycled before they start getting weird and smelling.

msbreadbaker's picture

Wow! What a bunch of interesting information. Especially the possible deterioration of the plastice container. All suggestions sounded reasonable. If you come to a conclusion, will you please post it. Thanks, Jean P. (VA)

Urchina's picture

Thanks for the ideas, everyone!

I only buy unbleached flour, and the brand I currently use most is King Arthur. I do occasionally buy unbleached organic flour in bulk from a local store that carries it, and the brand of that one is Giusto's. When I buy the King Arthur, I buy in 10-lb paper sacks, and none of the sacks ever show signs of being exposed to any liquids (no buckling or discoloration of the paper). The flour in this bin is never self-rising (I've only bought self-rising once, in a biscuit experiment). 

Yesterday I dumped the rest of the bin, washed the container (which is an older plastic container, but more on that later) and bought a new 10-lb bag of KAF. As I opened the bag, I got hit with the same smell as what I had dumped. These bags were purchased at a busy warehouse store (S&F) over two months apart -- it's unlikely they are the same batch. It made me realize (or wonder) -- it's possible that my sense of smell is changing and that I'm picking up (or interpreting) odors differently than I used to, and that what I'm reacting to in the smell isn't actually ammonia but something else that triggers the same response in me. 

So I went ahead and baked with the flour yesterday -- and the final baked goods were just fine. No off flavors or odors, for me or anyone else (even after sharing the experience). I'm going to have my husband and baking-goddess-friend check out the flour for their reactions -- it's possible this mystery is literally all in my head, and mine alone. 

Anyone else ever have this happen to them? 



gary.turner's picture

Your olfactory sense is composed of thousands of chemical receptors.  What these sensors detect and how your brain interprets the combinations tell you what you're smelling. There are a potload of things that can alter your sense of smell; smoking is likely the best known of these. Smoking deadens the sense of smell, quitting brings it back. Likewise, disease can alter your senses. One serious cause is stroke. If it is just you that senses ammonia, you might want to tell your doctor. It may mean nothing, but will provide another baseline datum for your records.

One possibility I haven't seen mentioned in this thread is the breakdown of protein. Ammonia (NH₃) is a byproduct of protein lysis, primarily by either bacterial or enzymatic (e.g. protease) action.



Yerffej's picture

Like all of our senses, the sense of smell can be deceived for any number of possible causes.  I would definitely have a few other sensitve smellers take a whiff of this flour.  I am curious about the outcome.


Urchina's picture

So my baking-goddess friend was over today, and I had her smell the flour. Her instant reaction was "This does NOT smell right. It smells.... musty." On reflection, I think her description is a more accurate one than my previous "ammonia" smell -- though there are definitely related scents there. 

So I've had two batches of King Arthur smell like this -- and exactly like this. They have been purchased from the same store. The flour isn't rancid; it had a use-by date of December, 2012. Unfortunately, I recycled the package. 

I'll probably e-mail KA flours and contact the store I bought it at. And I won't be buying flour from that store again. Which is a shame, since we blow through the flour and that place was the least expensive and most convenient around. 

Still -- the mystery remains -- how did that smell get into that flour? 

LindyD's picture

You mentioned the seller is a busy warehouse store.  You might find the answer if you could examine the location where the store keeps its flour before moving it to the shelves.  

Flour must be kept in a dry, cool area (off the floor) and away from anything with a strong smell.   Flour does absorb odors.

I try to buy KAF when it's on sale, so I'll stash the excess bags in zip-lock bags until it's time to pour it into my storage containers - which are glass with a screw-top lid.  

Yerffej's picture

Based upon your "musty" description and the fact that I strongly doubt that it came from KA smelling musty, I would have to suspect improper storage after KA and before you got the flour.


rprestidge's picture

I just found an old earthenware jar which had some white flour in the bottom.  It had been sealed up with a cork stopper for several years - maybe five years, or even more.  The flour had gone beige in color and smelled terrible.  The main flavor was definitely ammonia (I am a chemist by trade so I am quite confident about this).  But there was an underlying note of some short-chain fatty acid like propionic acid or butyric acid.  (These acids are what give vomit its distinctive smell.)

So I agree with the suggestions above that improper storage can make flour smell like ammonia.  Probably some bacteria or fungus that has broken down the protein in the flour.  I wonder if dampness is a factor?  Usually microorganisms can't thrive in flour because it is too dry.  But if it gets moist then things can start to grow....