The bag was packed tight. It was in standard flour sack and inside a thick cardboard shipping box, there were a few hundred pounds on top of it, on a skid. It was not wrapped in plastic. Mostly the room is pretty dry, but there was humidity in the summer.

When I open the bag it is hard like concrete, but breaks apart once I start busting it up and its light, fluffy once I crush it in my hand. I think there might be a light must scent to it, but its sort of tricky, like is it there or not, seems to disperse after a little while. Color is good.

I am really interested in any seasoned opinion on this situation. I don't want to make anyone sick, I also don't want to over-react and toss out $100 worth of flour. I am going to test it also for rolls, I should have those in a few days.

Thanks! I think these responses cover it. I baked some bread to test from the same batch different bag today, Bread was good. I will test run the bag we talked about here in a few days as well as make sure my digestion/energy/flavor don't show any impacts. I broke up the chunks some and put in a giant plastic bag to see if it airs a bit or what. If any aspect of it fails I will make paper mache halloween ghouls. :)

  • 3
    Crust/solidity implies moisture
    – bob1
    Oct 15, 2022 at 7:59
  • 3
    Hi Breandan, we cannot tell you if it is "OK". There is no way for anybody to predict whether some food will make someone sick or not! The closest that can be stated whether the food is "safe", which is a very different thing. See cooking.stackexchange.com/tags/food-safety/info for details.
    – rumtscho
    Oct 15, 2022 at 11:03
  • @rumtscho Can you explain how "OK" and "safe" are different, please? On the face of it your "safe" is a lot more clear than anyone's "OK." Oct 16, 2022 at 19:45
  • Brendan, why not just bake some and see what happens? Won't the temperature rule out any queries about safety, leaving only quality of the bake… EG, how well it rises? Oct 16, 2022 at 19:47
  • 2
    @RobbieGoodwin intuitively, people expect "safe" and "unsafe" to be separated at the boundary of "will/won't make you sick". This is not the case; "safe" means that you can prove that your food was stored and handled under a predefined set of conditions known to not allow pathogen growth, and so it is a statement derived from your information about the food, not from something in the food, and also, most unsafe food won't make you sick. Predicting the "won't make you sick" criterion is intuitively better, but it turns out to be impossible - but people keep guessing, which is off topic here.
    – rumtscho
    Oct 17, 2022 at 6:33

5 Answers 5


It's impossible to say whether the four is safe for certain, given the conditions you describe it is likely fine but there are no guarantees. It's very possible that the flour has simply gotten compacted by the weight on top of it rather than from moisture, if the flour is dry it's much more likely to be safe. A year is a long time to store flour, though, so you may be smelling some of the oils in the flour having turned rancid - even if it's safe it may not be good.

To test for moisture you need an accurate scale and an oven. You take a decent sized sample, say 100g, spread it out on a tray and bake it for an hour at medium temperature (130C/260F) to drive the moisture out. You weigh it straight after taking it out of the oven and measure the difference. If the water content is above 15% it's been exposed to too much moisture. So if you bake 100g and it comes out at 86g or higher at least you know it's not damp.

If you do decide to use the flour you'll want to sift it at least once to aerate it and bring back its fluffiness.


From your description it sounds more like the flour was simply packed tightly rather than getting damp, but even if it remained dry, I think you will likely find the flavor is off.

You said you don't want to throw away $100 worth of flour, but ask yourself if you would pay $100 for a 50 lb bag of flour that you knew was a year old?

If you are looking for a way to repurpose the flour rather than just discarding it, you could always use it to make salt dough for crafting, or donate it to a school for this purpose.


Water activity of the flour would be the determining factor for if the flour is safe or not. From Colorado State University's page on flour safety:

Flour should be stored in a cool, dry place in airtight containers. All-purpose, bread, and cake flours will keep for 6 months to 1 year if stored at 70°F and for 2 years if stored at 40°F. Wheat flour should be kept refrigerated or frozen, if possible. Naturally occurring oils in flour, particularly whole wheat flour, oxidize when exposed to air, especially at room temperature, and cause flour to turn rancid.


Flour is a low moisture food with a water activity (Aw) level of 0.87 or lower. Generally, an Aw of 0.95 or higher is required to support microbial growth.

Flour will typically have a water activity in the range of 0.35 to 0.52 [1, 2]. Given that moulds are inhibited at as low as 0.70 Aw, if there are no signs of mould growth on your flour, then the flour has not picked up enough moisture to allow harmful bacteria to grow.

The shelf life recommendation relates more to oxidative rancidity, a quality issue. If the smell is faint and dissipates to a point you're comfortable with, and the flour is not part of a batch recalled for contamination, then the flour is safe to use without causing illness.

If you want to be more sure, water activity can be determined from moisture content at home using the heating method suggested by GdD using the relations below (from relatively high humidity Bangladesh):

flour isotherms Moisture sorption isotherm of flours, including wheat. From Ahmed & Islam [3]

[1] The Case for Water Activity as a Specification for Wheat Tempering and Flour Production.
Brady P. Carter, Mary T. Galloway, C.f. Morris, G.L. Weaver.

[2] Water Activity in Foods: Fundamentals and Applications - Appendix E: Water Activity Values of Select Food Ingredients and Products.
Shelly J. Schmidt, Anthony J. Fontana Jr.

[3] Moisture Sorption Characteristics of Selected Commercial Flours (Wheat, Rice and Corn) of Bangladesh.
Md Wadud Ahmed, M N Islam.


Simple: taste it.

Stale flour tastes notably bad, even in its raw state. If you're still not sure, get a small bag of known-fresh high-quality flour, and compare tastes. Rancid flour will have notable off, bitter flavors.

If it tastes fine, then it is highly unlikely that anything has happened to the flour to make it a contamination risk. All flour should be cooked, in any case, and the bacteria that infect flour (such as salmonella and e.coli) do not survive cooking.

(spit out the raw flour after tasting. Eating raw flour is never a good idea, even if it's fresh)


As it's generally recommended to use sieving before use, you will find if there are some insects inside, and whether it is still "fluffy". Also as recommended already, try the taste. The age alone should not be a problem.

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