The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

nutrition of flour after being milled....

DanOMite's picture

nutrition of flour after being milled....

I had a co-worker tell me today that after 24 hours of being milled that all nutrtion in flour is lost. Is there any truth to this? I'm really quiet curious to know...I remember reading in peter reinharts whole grain book that after flour is milled it has to be used within like 8-24 hours or you can't use it for like two some odd weeks.  That could make sense because obviously its going through a shock of being a berry into powder. But I don't see how its possible that all nutrtion is lost. I've been using King Arthur whole grain flours and everytime I use them and eat the bread my fiber levels are up higher.

Could anyone share some light on this

Or should I just try to ignore what I heard because its not true?

I hope sombody's got some answers because this bugs me...

Thank you for all your help in advance...


blaisepascal's picture

There are some important ways in which that assertion is wrong.

For one thing, folks who say things like that forget that sugars and starches are nutritive.  They assume they are valueless filler.  In truth, they are what has made bread "the staff of life" for millenia.  

What they are concerned with is the destruction of vitamins, minerals, oils, and proteins.  Some, but all, are vulnerable to degredation with time.  But 24hrs too fast.

But without protein, bread won't make a risen dough, as gluten is a protein.  Since people make bread all the time with store-bought  flour, clearly the gluten isn't destroyed. 

It's well known that freshly ground whole wheat flour, if stored at room temperature with plenty of access to oxygen will, after a few weeks or months, go rancid.  That rancidity is caused by the oxidation and breakdown of the oils in the wheat.  Before it goes rancid, the oils are still there.

While there may be some minor degradation of nutritional quality, it's not significant over the first 24 hours.

rockfish42's picture
Is a detailed description of flour nutrition specifically related to sourdough and whole fresh flours. While there is some degradation of nutrient content, if you maintain an otherwise healthy diet it's unlikely you would see any negative effects. Some of the information in the article is slightly suspect as the sources are rather old.

Yerffej's picture


Thanks for that link as it is a really nice article.


prairiepatch's picture

I enjoyed the article too Rockfish.  Thanks.

Here is another article on the same subject.  The following few lines are from that article.  Although how do you know how acurate anything is on the internet. Right?  Again these next words are not mine but come from that article with the link to it following.

"A little research bore out our family's observations. It turns out the original whole wheat grain is a power house pellet chock full of nutrients, yet if you buy pre-milled flour in the store up to 88% (1) of some vitamin and mineral content is already lost, and the remaining nutrients are contaminated with bleaches, caramel coloring, emulsifiers, mold retardants, texture agents and a host of other...",+the+quicker+you're+dead-a0133411456

subfuscpersona's picture

DanOMite on September 22, 2008 wrote:
I had a co-worker tell me today that after 24 hours of being milled that all nutrtion in flour is lost. Is there any truth to this? I'm really quiet curious to know.

Commercial flour milling is a complex subject and, without the details of how your store-bought flour is milled, stored, aged and transported, you will *never* arrive at a satisfactory answer.

Furthermore, if you purchase whole grain *flour* (such as 100% whole wheat flour) you will be generally clueless about the quality of the grain purchased, the (commercial) milling techniques, how long the flour was stored and the time elapsed between milling, packaging, transportation, and storage at the local outlet (your supermarket or coop or whatever). Your only hope is to purchase flour from a reliable supplier and to know the flour specifications of that brand of flour.

Home milling is a different subject. In this case, you, the baker, purchase whole grains and mill the quantity you need for one baking.

As a *home miller*, you control your flour. You are responsible for the quality of the wheat (or other grains you purchase). You are in control of the storage conditions of your grain and the flour you mill from it.

For home milled flour, do remember that the outer portions of the endosperm, the bran coating and the germ contain the bulk of the *minerals* in the grain. Minerals are not subject to destruction by heat. You will get the full mineral complement of your grain in your flour.

Vitamins, on the other hand, *are* subject to degradation by exposure to prolonged heat. This is *almost never* an issue in home milled flour. Around 140F is the magic number where vitamins *may* be destroyed. In repeated tests using an electric flour mill (a Nutrimill micronizer mill) and measuring the temperature of the milled flour immediately after milling with a digital thermometer, I never found the temperature of any flour to be over 130F. Furthermore, the home miller can easily and rapidly dissipate any heat in fresh milled flour simply by stirring the flour and /or pouring it from the mill's flour receptacle into a separate bowl.

The bioavailability of minerals in whole grain flour (especially whole grain wheat and rye flour) *is* affected by the techniques used to make bread dough. Bioavailability refers to the ability of humans to absorb and make use of nutrients in your flour. There has been a lengthy discussion of this topic on TFL and I will find the thread reference for you if you are interested.

Lastly, be cautious how you interpret and research information on this topic. There is a great deal of incorrect information on the "web" on this topic. A great deal of it is fueled by vendors who are selling some product, and the rest is the result of writers who mindlessly repeat this mis-information.

You can, in fact, find valid scientific studies on the web that address these issues. However, to properly interpret them in context, you must have some grounding in the scientific method and statistical analysis.

This general topic periodically rears it's head on TFL and other forums. I am sympathetic with bakers who wish to produce good tasting bread with maxiumum nutrition. However, there is clearly a great deal of mis-information that gets repeated and wins credence simply by repetitition. Always ask yourself whether the information you read is from a trustworthy source, is supported by *facts* from a reliable source and - last but not least - sounds reasonable.


subfuscpersona's picture

DanOMite on September 22 wrote:
I had a co-worker tell me today that after 24 hours of being milled that all nutrtion in flour is lost. Is there any truth to this?
Mike Avery is a professional baker and teacher. He is a long-time member of TFL, and every post of his I have ever read is right on target and contains valuable information. A very similar question to yours was posted by TFL member "staff of life" on June 26 - see Mike's reply to that query can be found at but, for your convenience, I'm going to repeat it here... ===== from Mike Avery =========== The only people who talk about the nutrition value of freshly ground flour are people with a dog in the race. People who are selling mills, freshly ground flour or baked goods made with freshly ground flour. The web pages that promise good health and say, "all we changed was our bread" are inevitably pushing freshly ground flour or the equipment to make it. Is it really better? I don't know because I haven't seen an independent study. I'd love to see some. Annecdotal evidence IS important, it is persuasive, but it isn't proof. All too often you find that someone who had health issues changes a lot of things at once and doesn't think about them. The one that took a lot of time was grinding the flour and baking the bread, so that's what they focus on. I'd like to see chemical analyses of the flour when it's freshly ground and again every day or two for a month, and every week or two for a few years. Or even with less frequency, but still offering some degree of history to the same flour. And then I'd like to see some sort of study as to what impact that would have on people. My take on the matter? From what I hear somewhere between 120 and 140F is the critical temp. You don't want to go past that. And neither my micronizer mills nor my KitchenAid mill raise the temps too far. The only thing I know of that decomposes is the fatty acids in whole grain flours which will go rancid. Rancidity is distatesful but it is not a short term health risk, though some people point out the oils are oxidised and could speed oxidation in your system. Still, if you're hungry you can eat goods made with the rancid flour without becoming ill. It won't be appetizing though. How long does a whole grain flour last? It depends on storage conditions, but 6 months to a year at room temperature, if memory serves. The breadmaking characteristics are another interesting matter. Many people like to make bread with freshly ground flour, flour "still wriggling with life" as Alan Scott put it. And it works pretty well. However a few days later, that flour can be very hard to use - the dough is so elastic it is very hard to work with from all reports I've heard. At that point, letting the flour age a few weeks will restore it's baking characteristics.
motomuffin's picture

I am new at all this bread making stuff.   

Just curious but why are people worried about the temperature at which you grind the wheat when it's going to go in a hot oven in a matter of a few hours right?  Won't that have the same affect?

gavinc's picture

I don't know what the situation is in USA, however in Australia a minimum amount of nutritional information is law on all food products.  I use this information to quickly see the protein percentage of the various flours as they have to show the grams per 100 g portions as well as suggested serving sizes.  I've uploaded a couple of flour labels to give you the idea. 

bread flour 11.9% proteinGeneral purpose unbleached 10% protien

jasonla's picture

I think you could cool the wheat in the refrigerator before milling so that it doesnt heat up as much. You could always add vitamins to the bread and make it very healthy more then what any of the ingredients provide.

beeman1's picture

If the the wheat is milled and then made into a soaker or biga will the oils oxidize?

TorontoFlour's picture

Well I've been googling for hours and read this informative post too. But I am still puzzled:

Everything I read says that the oils in the germ of the wheat in whole wheat flour will go rancid in a few days, And then I hear this from a whole wheat flour miller in Ontario, Canada (in response to an email from me):

"When using a stone grinder the oils in the germ are dispersed into the flour at a lower temp and without the electrical charge that is produced by steel roller mills causing the flour to be stable. We offer a shelf life of over a year. We actually have some consumers that require the flour to be at least a few months old before they will use it due to the natural aging process. So the bottom line is our flour does not need refridgeration."

but now DanOMite, above, says "How long does a whole grain flour last? It depends on storage conditions, but 6 months to a year at room temperature".

So, my questions are:

1. Is it then true that the shelf life, which is based on how long it takes for the oils in the whole wheat flour to go rancid, is based on the milling method? ie steel roller vs stone grinders?

2. If it is steel rolled, just what is the shelf life?

3. Do processors that sell whole wheat flour that is steel rolled and has not had the germ or germ oil removed and is sitting in packages at room temperature on store shelves put some type of preservative in it to make it last longer? If so, what?

Thanks, but I want to get to the bottom of this!

niceguy1129's picture

I am a baker and a chemist. The unsaturated and polyunsaturated oils in any whole wheat flour, whehter ground with a stone or roller mill, will go rancid (a process of oxidation) over time. Rancidity produces off flavors and odors in whole wheat flour.

When the kernel is ground in the mill, the oils stored in the germ are dispersed throughout the flour. Several things influence the storage life of the flour; temperature, oxygen content, and enzymes. Rancidity of the oils increases as the temperature increases during storage - this is why many bakers store their flour in the freezer after it is ground. The more oxygen limiting the container the greater the shelf life of the flour. Additionally, there are enzymes present in the kernel (lipases, lipoxygenases) that also enhance the rate of rancidity.

Stone grinding flour happens at a lower temperature than from a roller mill. This lower temperature is a positive for preventing 'heat' damage to the oil and the increased rate of rancidity related to a higher temperature. But, the higher temperature related to roller milling also destroys more enzymes related to inducing rancidity. So - stone milling is at a lower temperature that protects the oils from rancidity, but the temperature is not high enough to destroy the enzymes. Roller milling is a higher temperature process that probably enhances rancidity of the oils, but it also reduces the amount of enzymes that encourage rancidity. Unfortunately, there is no one answer for your question about storage life of whole wheat flour since many factors can change the rate of oil rancidity.

I have a stone mill that I use in my baking. I don't use any ground whole wheat flour past one month of age.   

I am not aware of any manufacturers who add preservatives to commercial whole wheat flour sold in grocery stores. By law, the manufacturers must list every ingredient they add to the product. Most added ingredients are vitamins and minerals used to enrich the nutrititive value of the flour, and most of these are added to all-purpose or unbleached flours.

Hope this helps. 

TorontoFlour's picture

Thanks! That is a great help in understanding this. And the fact that you are a baker and a chemist adds a lot of depth to your explanation.

However, I am still wondering about a couple things. I contacted both King Arthur and Bob's Red Mill, both of which manufacturer whole wheat flour (in addition to the local company I mentioned in my first post).

Bob's Red Mill whole wheat flour is ground using 100 year old stone grinders and packaged in air-tight plastic bags. They advised me via email that it has a shelf life of 24 months (presumably following grinding, but they did not say this) and that they advise storing it in the refrigerator or freezer. They said it would not go rancid in a week. When I further asked how they were able to offer this shelf life and whether they had in fact tested it for rancidity at various times after milling or whether it was simply a rule of thumb they followed they said it was a rule of thumb. Furthermore, they said they stand behind their product and one could return it if one was not 100% satisfied. They all said that if refrigerated as they instructed on the package, that 'it will taste as fine as the day they purchased it'.

While it's great that they stand behind their product and recommend it be refrigerated, this did not give me the comfort that the product does not deteriorate and go rancid by 24 months or much earlier. Nor do I understand how if can taste as fine as the day I purchased it, 24 months later.

I also emailed King Arthur. They explained to me that they use steel rollers to grind the flour but that they did at a low temperature which did not affect that grain as much as a high temperature. When I further inquired the customers service rep told me the information they had given me previously was wrong and that they use a high temperature but then they cool the wheat very quickly so that the high temperature does not affect the wheat. I then asked how they cooled the wheat and they replied using 'lots and lots of air'. When I asked them what temperature the wheat rose to when being ground using the steel rollers they said that it was 'proprietary information'. (I am not sure why the temperature is so proprietary as many companies use steel rollers). When I asked them how they knew what their shelf life was and if they ran tests on rancidity at various times they gave a similar answer to Bob's Red Mill.

The local manufacturer I talked to (who uses stone grinders) even told me that in addition to a higher temperature, that steel roller mills disperse an electrical charge into the wheat that causes the flour to be less stable than when ground by stone. I had never heard that before.

So, just to summarize, these are the questions that I still have and maybe you could help me with:

1. Is it really the absence of the electrical charge and not just the lower temperature that causes wheat ground by stone to be more stable, or is it not even stability that is the issue, but rather the destruction of nutrients that high heat and possibly an electrical charge causes?

2. Once one heats the wheat to a high temperature, as King Arthur does using their steel rollers, does it really matter whether it is then cooled down immediately afterwards. Isn't it the fact that the wheat go to that temperature that affects how quickly it will be come rancid (and possibly destroys many nutrients) rather than they cooled it down afterwards. And, they are cooling it down, not refrigerating or freezing it.

3. Can Bob's Red Mill really make the claim that their stone-ground whole wheat will taste the same 24 months later as they day you bought it? They are not adding any additives to preserve the wheat so the wheat would be the same as that anyone else ground using a stone grinder. So, why does Bob's Red Mill's product have such a long shelf life? They do use what appears to be good packaging, which is an air sealed plastic bag, as opposed to the paper bags that some other manufacturers use that do not appear to provide a complete air seal. And, it fine that Bob's Red Mill provides a guarantee but I would rather not have to return something.

4. Why do people who grind their own wheat say use it as soon as possible or freeze it immediately (and the previous poster does not use ground whole wheat flour past one month of age) yet all of these large manufacturers claim that the same stone ground wheat can be used even a couple of years later. I would assume that if people are advising using the wheat immediately or within a month there must be some substantial deterioration that is noticeable in taste. Or is it just that the nutrients might not be there as much as if one used it earlier.

I guess the final question is should people really care about using fresh ground whole wheat? Am I splitting straws here?





When using a stone grinder the oils in the germ are dispersed into the flour at a lower temp and without the electrical charge that is produced by steel roller mills causing the flour to be stable.

proth5's picture

I always like to get my oar in on one thing that confuses some home milling enthusiasts.  Steel roller mills and steel burr mills are two different things.  Many folk decide that their home mill must have stones because it is cooler than "milling with steel"  Yes, it is a cooler process than milling with steel roller mills.  No, it is not subtantially cooler than milling with steel burr mills.  I've got a burr under my saddle (so to speak) on that one because I mill with steel burrs and I get tired of people telling me that they are no good.

As for the aging of whole wheat flour, I have baked with flour ground within the hour, flour ground 18 - 24 hours ago, flour ground a week ago, and flour ground a month ago.  I ran as controlled experiments as I could and did not find that baking qualities differed.  So I am not signing on to the baking folklore about "within 36 hours or not for two weeks."  Studies done in Japan claim that for gluten development aging whole wheat a month a room temperature is optimal.  (I've lost the actual citation, sorry.)

Taste, however, degrades pretty significantly over time.  I'll settle for the 18-24 hours when I do whole wheat because I don't like to mill first thing in the morning, but the closer to milling the better the taste in my opinion.  So, I care, because I like to mill and I like the taste of fresh.

As for nutrition, I won't get wrapped up in that discussion.  I am not suffering from any condition that traces itself to lack of good nutrition, so I'm going to eat what I like and let the food fight it out inside. However if this is really bugging you, let me suggest that you can send samples of various flours at various ages to CII laboratory services  I have used them for flour testing and they are more than happy to take samples from individuals and test them.  They have a number of nutritional tests available and do a pretty quick turn around.  They might even be able to do an experimental mill for you.  It's not without cost, but if you have to know, it might be worth the money...

Hope this helps.

niceguy1129's picture

Thanks for the great questions. I am not a milling specialist nor a grain scientist, but I do understand some things about chemistry and science. Answers follow:

1. The notion that steel mills, whether roller mills or burr mills, create an electrical charge that deteriorates the quality of the flour is almost laughable. Even if there was a measurable electrical charge imparted to the flour during grinding, it would not alter the rate a rancidity formation in the natural oils in the flour. I repeat from my first posting, rancidity of fats and oils is influenced by temperature, oxygen, and the degree of unsaturation of the fatty acids. For example, butter sitting on the kitchen counter will go rancid faster in the summer than the winter (assuming the oxygen levels in the air and the degree of unsaturation of the butter are unchanged, and that your kitchen is warmer in the summer than in the winter).

2. The heat generated during the grinding may have an impact on the nutritional quality of the flour. A flour miller would have to get to extremely high temperatures (> 200 F) to get significant reductions in vital nutrients. The nutrients most susceptible to high temperature are the B-vitamins, vitamin C, some fat soluble vitamins and the oils. One would have to go to outrageously high temperatures to destroy the protein, carbohydrates and minerals in flour. That being said, when KA grinds their flours (which may result in temperatures higher than when using a stone mill) the destruction of nutrients is likely minimal and cooling the flour after milling would be a positive step in the process to prevent nutrient loss. My only fear of generating a higher temperature during grinding is that it may enhance the rate of formation of rancid oils in the flour. Once rancidity is inititated, it is very difficult to stop unless oxygen is limited or the temperature is decreased significantly.

3. I tend to agree with Bob's Red Mill that the practice of sealing their products in air tight packaging leads to longer product stability and decreases the opportunity for the development of off-flavors or off-tastes. When oxygen is removed or greatly limited, the ability of unsaturated fats to become rancid is lost. By definition, rancidity is the addition of oxygen to the chemical structure of unsaturated fats and oils that causes the oxidation of fats and oils (a process called peroxidation). The peroxides that result from this oxidation then break down into other chemicals which lead to off-tastes, and off-odors. Additionally, rancid oils can destroy other nutrients (mainly fat-soluble vitamins). There are chemical tests that can be run to determine the level of oxidation of the fats and oils in any food matrix. Bob's Red Mill could easily measure the levels of these oxidation compounds in their products and from that determine shelf life - 24 months of shelf life is reasonable when using oxygen excluding packaging.

4. In the absence of oxygen excluding packaging, storing the ground flour at freezer temperature limits the amount of oxidation that can occur since the chemical reaction is slowed by the low temperature (<20 F).  Exposing ground whole wheat flour to room temperature, in a normal oxygen containing environment, means that the oils in the flour will progessively become rancid, imparting off-flavors and off-odors to the flour and hence to the baked product. Whether that happens in 1 week, 1 month, or 1 year depends on the temperature, the level of oxygen, and the unsaturation of the fats.

My own personal experience is that freshly ground whole wheat flour is best. When I have used whole wheat flour that was over one month of age, I noticed a change in the taste.

Great discussion. Glad to answer any more questions about this topic.



TorontoFlour's picture

Those answers are fascinating and really helps one understand what is going on. I have searched elsewhere quite a bit for that kind of detail about what really goes on when and after wheat is ground but did not find much. Of course now I have more questions!

The benefits of air-sealing the package would cease once the package is opened, so I wonder then how Bob's Red Mill is able to claim the product will taste as good as they day it was bought 24 months later even if it was refrigerated or frozen after opening. Wouldn't that really depend on when you opened the package?

I am not sure if King Arthur's package is even air sealed as I haven't been able to get my hands on one. It appears to be a paper bag so maybe not. I am not sure whether they recommend on the package refrigeration or freezing after opening. But, they claim a 6 month life I think. But again, are they not just guessing too?

Also, I know that Bob's Red Mill claims the product will taste the same 24 months later but it appears they are just guessing as they admit they don't do any tests and just use a rule of thumb (which maybe has been derived from customers complaints). Is it not likely that the product has, by that time or much earlier, gone rancid and customers just really don't know as they just use the flour without paying much attention? 24 months is a long time, given the practice that people like yourself and others follow of using the flour immediately or within one month after grinding. Before I started getting serious about baking I didn't even know that whole wheat flour could go rancid so I wouldn't even think to watch for it. I'd just use it. Once my Komo Magic grinder arrives that certainly will all change.

The local manufacturer (the one that told me about the electrical charges) said that some of his customers like to let the whole wheat flour sit for 3 months after milling because they like the taste better. I take it then they like it when the flour has deteriorated a bit and gone a bit rancid. What else could it be?

Thanks for your valuable input.



niceguy1129's picture

Glad things are getting clearer.

I'm sure Bob's Red Mill would tell you that the product inside the sealed bag will have similar taste as freshly ground product if you stay within the 24 month shelf life. Once you open the package, the deterioration will start. The date codes on the bags relate to shelf life of an unopened product. Once it is opened, it should be used within a month for best taste.

KA uses paper packaging, therefore it is not air sealed.

In flour milling, a common practice is to separate the germ and bran from the endosperm. This removes the oils in the wheat kernel starchy portion (endosperm) and generates white flour. The white flour, if allowed to age 2-3 weeks will eventually get whiter from oxidation. This is what is known as unbleached flour. The taste of unbleached flour does improve when allowed to mature over time. Bleached flours have better baking characteristics than unbleached - related to gluten formation.

There are some websites that describe the wheat milling process. Do a Google search and you will find good information.

TorontoFlour's picture

Actually this local manufacturer was talking about stone-milled whole wheat flour when he mentioned that some like to let is rest for 3 months. I didn't think that that made whole wheat flour taste any better!

snihan's picture

Reading through this post a lot of people are comenting on how the grain is ground, where depending the high heat of the grinding process it can kill nutrients.  One person asked a question that has been in my head for quite some time, but there was no response to their question.  Most of my recipes call to bake my bread at 350/375 degree's, now what nutrients make it through that baking process?  Earlier it was stated that nutrients are killed in heat over 140 degrees. 

So if home milled grain or store bought grain is being used, does it matter, becuase both are going into high heat ovens? 

thanks again for any insight you can offer!



JBeddo's picture

I am one of those home milling enthusiasts and got into milling my own flour for several reasons. One of those reasons was my husband allergies. He has problems with the agent that is commonly used to keep flour from caking. What I learned is that many of the vitamins and minerals are oxidized away after the first 72 hours after milling. Now I know you have read lots of stuff here but the thing that convinced me this is the real scoop was that Sue Becker of found a lab that would test the bread baked from freshly milled flour to actually see how much of those vitamins and minerals were present in the bread and therefore available to the consumer. Sue has a degree in food science and offers a free CD where she lectures on the subject with any purchase on her site. It's called "The Bread Idleness" you have to put it in your shopping cart even though it's free.

Not only did the results from the lab turn out to prove the idea that there is a lot of nutrition lost in that 72 hour window but anyone in our house can give testimony to our believing that we all feel better since we made the switch. One thing I didn't count on was how much better the baked goods taste. I use freshly milled flour for everything not just breads. I have even made cakes with white wheat berries and they are good where when I tried to convince myself that a whole wheat cake taste good I never quite choke that down, admittedly a flavored cake works better like chocolate or even lemon.

Anyway that's my 2 cents on the subject. JQ

Jo_Jo_'s picture

Thanks for the link to Sue's site.  I have been seeing things online talking about soaking fresh ground flour  before making it into bread, and in fact am making a couple loaves right now that the flour soaked for 20 hours before making into the actual dough.  This is to remove the harmful phytic acid, but from reading Sue's site it is giving my the "other" side of the coin so to speak.  There is definite evidence that the opposite is true, that phytic acid might be helpful in a lot more ways than I had first realized.  I hate when I can only find one side of an issue, so having the other side of the coin really helps a lot.