The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

How are whole grains for home milling treated for granary pests?

Joshua in Seattle's picture
Joshua in Seattle

How are whole grains for home milling treated for granary pests?

How are whole grains for home milling treated for granary pests? And what implications does this have for the home baker?

Here's what my internet research tells me:

Mills used to use Methyl Bromide, a carcinogen, to fumigate flours. Now, they seem to use a combination of Sulfuryl Fluoride and heat. I don't know if mills use these processes on just flours or also on unmilled grains. An alternative organic method seems to be to spray the grains with diatmaceous earth, a ground up prehistoric arthropod shell derived from the sea that kills insects mechanically. This method is considered very safe in the gardening community, though it becomes ineffective when wet, and is basically just a form of calcium.

If granaries use heat treatment on flour, what are the implications on whole grain nutrition? Of what importance are the enzymes that will surely be killed by 140 degree F heat treatment? (sometimes mills use a lower temperature, but I saw this temperature in industry literature as the "high end") Surely we're going to kill off the enzymes anyway when baking. I know living enzymes can cut fermentation in half (not always a good thing), so there's at least some impact. Do the enzymes also help free up nutrients during the ferment? 

I am not a fresh ground zealot, but I do see strong evidence that whole grains, store bought or ground at home, are more nutritious, and pesticide residues in flour may be another reason for grinding your own. I just don't understand what's used to control pests in organic grains, or what benefits/complications these treatments might have for home bakers.

Any ideas?

Joshua in Seattle

GlendaLynne's picture

I live in Australia and buy my organic wheat and rye grains from Kialla Foods ( ). The product specification for each of these include:

There are no known risks associated with the handling or processing of this product. Post harvest grain is cooled by night aeration for 14 days in silos then fumigated with Carbon Dioxide to a level of 37.5% for 10 days. Once the grain is cleaned, processed and packaged it is stored in cool rooms at a maximum temperature of 11 degrees celsius. These rooms are dry and free from toxic chemicals, odours, insects and rodent infestation. It is recommended that product be stored under constant cool, dry conditions to maintain optimum freshness. No responsibility is taken for product if stored in humid, hot, dusty or infested storage. Our recommended shelf life for this product is 24 months after the production date but we will accept no responsibility for infestation once product has been accepted into the customers's storage facility.

I do not know how relevant this is in your part of the world.

I always freeze my grains for a few days after I get them, just to be doubly sure that I do not introduce extra unwanted protein, but have never had a problem. Storage is also important - food grade plastic drums with very good seals.


flourgirl51's picture

We grow and sell our organic grains and have never had a complaint of customers receiving buggy grains. I think that the care we take in the cleaning and handling of our grains and equipment is the key. Our grain bins are cleaned out between loads of grain as is our other machinery. The semis used to haul our grains to the organic bagging facility have to have clean out affidavits.  Our grains are triple cleaned. After they are bagged they are kept in a chemical free, rodent free, temperature controlled environment until they are shipped out. Once they leave our facility we have no control over how customers store and handle the grains but we do suggest that they keep them in a cool, dry environment. Some people store them in buckets with Gamma seals which helps to keep out humidity. Some people in hot humid climates keep them in the freezer or refrigerator.

In this area of the country even those farmers that store their grains in the bins would have a kill off of insects due to the natural temperatures that we have here in the winter months. For example- it is 28 degrees below zero this morning!

Just because something is labeled organic doesn't mean it was handled properly just as there are differences in the way conventional grains/flours are handled. The difference is though that you won't find any contaminants such as the chemicals that you mentioned added to organic grains and flours. Our sprouted grains are dried at 95 degrees to maintain  the nutritional integrity of the grains. Our flours are ground at low temperatures also for the same reason.

The taste of bread made from freshly ground grains as well as the aroma is amazing.


Joshua in Seattle's picture
Joshua in Seattle

What an excellent and informative website you run. I understand you don't fumigate your grains, and that you credit clean equipment for most of your success. However, here are two follow-up questions:

First, do you also use Diatamaceous Earth (DE) in your organic bagging facility, or anywhere else along the line? I am not against DE, but would just like to be able to state accurately which organic methods are used in the production of organic grains and flours.

And second, can you describe the process of "triple cleaning?" Does this simply mean running the grains through a sieve three times to remove stones? Or are there two other types of cleaning? 

People are becoming less satisfied with "organic" for its own sake, thanks to Michael Pollan, and want to know details. I'd like to be able to speak confidently on these topics.

Joshua in Seattle

flourgirl51's picture

The only crops that I have used Diatomaceous earth aka fossil shell flour on were cabbage and broccoli to control cabbage loopers.  Some farmers that have livestock feed DE to their animals to prevent parasites in them.

  The grain is run through a grain cleaner before it is put into the bins to separate out weed seeds, chaff, stones etc and then cleaned again at the bagging facility before it is bagged and then I personally sift the grains again before I process the grains into flour to make sure that there are no kernels of grain with the chaff still attached. While this isn't necessary it is just an extra step that I like to do as I am a bit of a perfectionist.

I would like to say that while the verdict may still be out regarding the nutritional value of organic versus conventional foods the main reason that we choose to farm using organic methods is that we have seen first hand the damage that the use of chemicals does to the environment. What goes into the soils and water eventually gets into the food supply. We have seen whole lines of mature trees die all at once  on a large conventional farm in this state due to the overdrift of chemical sprays  over the years on that farmers' fields. A family friend raises bees commercially in Wisconsin and recently had 200 hives of bees killed from a spray that the farmer there used on his soybeans and which came in contact with the bee hives.  Chemicals are poison-period and we choose not to use poison on our crops.

Some final thoughts - there are different methods of harvesting grain crops.  We use a straight head to cut the grains that go through our combine which means that our grains are cut while they are still standing upright and after they dry naturally on their own.  Some farmers use the method of swathing their grains first which means cutting them down in rows and letting them dry on the ground and then they use a pick up head that picks the dried swaths up off of the ground which are then run through the combine.

We prefer to use the straight head method because this also helps to prevent unwanted dirt from getting into the grain.

Organic  farming methods can vary from farm to farm just as conventional methods can vary from farm to farm. There are many variables to both methods and within both methods such as soil fertility, climate and general farming practices. I think that organics shouldn't be lumped together in one lot due to these variables.