An Innovative Mill for Special Grain

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Scotland The Bread is the first UK owner of a Zentrofan cyclone mill to make flour from Scottish grain for home and community bakers. We saw it during a visit to heritage grain growers, millers and bakers in Sweden in 2016.

What’s so special about it?

Unlike industrial roller mills which waste about 25% of the grain, or traditional stone mills which have a tendency to heat the flour, the Zentrofan mills whole grains into cool, ultra-fine wholemeal flour.

When grinding makes flour hot, the natural oils in the wheat germ (containing the important vitamin E) are thinned and exposed to air, vitamins oxidise and wholemeal flour begins to turn ‘rancid’. White flour from industrial mills has had the germ removed, so there’s little of any value in it to ‘go off’.

The key to the cool-running Zentrofan is that it mills whole grains into very fine wholemeal flour, conserving all the important minerals (iron, magnesium, zinc, calcium etc), vitamins (especially the B vitamins such as folate) and phenolic compounds that are found in the outer bran layers of the grain. These are the bits that are almost entirely absent in white flour.

Wholemeal flour is usually quite coarse and the pieces of bran, though tasty and full of nutrients, can break up the dough structure and lead to crumbly bread that is difficult to slice (and not to everyone’s taste). With the Zentrofan, this problem is reduced: the wheat grains are milled so finely that the resulting wholemeal flour feels as soft as white flour and is almost as easy to bake with. A real win-win.

How does it work?

A strong fan blows the grain round inside a small chamber made from basalt lava rock. When the particle size of the resulting flour is small enough, the cyclone carries it out into a bin, filtering the air flow through a large bag so that no dust enters the kitchen or bakery. Large particles of grain continue to be whittled down until they are fine and light enough to leave the chamber. Nothing is removed from the grain.

Cyclone milling was invented in the 1930s by Wilhelm Schulte, a German engineer with connections to the founder of biodynamics, Rudolf Steiner. At a time of increasing concern with the damage done to food by intensive processing, the mill attracted people concerned with practical public health through its ability to conserve the vitality of the whole grain in a meal that performs more like white flour than the wholemeal most of us are familiar with.

This is essentially an ‘intermediate’ technology, and as such a useful aid to food sovereignty. The laws of physics prevent the cyclone milling system working efficiently at more than about 20 kg per hour, so the Zentrofan is a tool for decentralised small-scale mills and community bakeries. The technology can’t be ‘scaled up’ and expropriated by giant mills – and in any case fresh milling needs to be done as near to the point of use as possible. Local control and reducing food miles (and carbon emissions) go hand in hand.

What is the flour good for?

Scottish heritage wheat generally has less of the stretchy gluten that has been bred into modern hybrid wheats, so it needs skilful handling – and slow fermentation – to give of its best as bread. Its great advantage is the flavour, sweet and full, that comes mainly from the outer layers of the grain that are completely conserved in flour milled by the Zentrofan. This fine wholemeal flour is very versatile. It can be used for every baking recipe, from bread to cakes and pastries. Check out our baking tips and recipes.

Where is the flour available?

Find our list of stockists and bakeries here. In the fullness of time, we hope to enable community-supported bakeries to acquire their own Zentrofan mills so that everyone can access the tastiest and most nutritious bread made from freshly milled, locally-grown, heritage wheat.

To preserve maximum flavour and nutritional value, flour should, ideally, be used within hours or days of milling. Scotland The Bread sends out freshly-milled flour twice a week by overnight carrier (for orders of more than one 1 kg bag). Any flour not used on the day of arrival can be stored in the freezer to conserve all its vitality. For ultimate freshness, you can buy the grain from us and grind it on your own mill.


Nature Save TrustBread for Good Community Benefit Society acknowledges the generous contribution of an Environmental, Conservation and Community Renewable Energy Grant provided by the Naturesave Trust towards the purchase of the Zentrofan mill.

12 thoughts on “An Innovative Mill for Special Grain

  1. Jonny Muir says:

    Looks really interesting. And I can see from subsequent posts you are still using the mill which is great.

    I am looking at ways of bringing local grains into local communities and this technology looks very promising. I am particularly interested in whether the technology could be used in a decentralised system of flour “vending” which connect producers (farmers) with consumers (either home or small bakers) in areas where they aren’t as lucky to be near you. Your thoughts would be gratefully received.

  2. Scotland The Bread says:

    Thank you for your comment, Jonny. Yes, I think the Zentrofan could be used fora system of fresh flour ‘vending’. Scotland The Bread already supplies one local shop with flour in bulk which is then dispensed with zero packaging. We hope to do this in returnable bins in due course. The ultimate would be for the mill to be set up in a shop or small bakery where it could mill away automatically overnight producing 25-75 kg of fresh flour by morning. This could go straight into the bakery mixing bowl or into home-bakers’ bags, bins or boxes. Different grains (rye, wheat, emmer, spelt etc) or the produce of different local grain growers could be milled on different days of the week. It would be simple to show exactly what today’s flour is, who grew it, in which field and what it’s best for baking etc.
    The bigger challenge for re-establishing such local networks is the absence of really effective small-scale grain cleaning machines. Either the farmer or the shop/bakery/food hub needs to be able to clean the grain to a high standard before it goes into the Zentrofan.
    I wish you success in your venture. If I can be of any more help, please ask.
    Andrew Whitley
    Chairman, Scotland The Bread, April 16th 2020

    • Emma Shires says:

      Hi Andrew, I just listened to the “miller is missing” cereal podcast episode on Farmerama and am really interested in the mill you have. Do you clean and sift the wheat on site yourselves? I would also be really interested in understanding your set up costs, so how much the mill cost compared to a more conventional stone mill of a similar output. Thanks,

      • Scotland The Bread says:

        Thanks, Emma. We don’t have onsite wheat cleaning yet. This is one of the roadblocks on the way to downsizing and re-localising farming and food processing. Grain cleaners for the commodity system process tonnes per hour, with scant regard for the needs of people who might eat the result – because, of course, they are usually cleaning grain for animal feed or, in Scotland regrettably, alcohol production. Our current problem is removing small amounts of fava beans from our wheat. These get in as ‘volunteers’ from the previous crop in the organic rotation and you would have thought that putting the grain twice through big commercial ‘dressers’ would have done a good enough job. But in fact, we need an intermediate-scale technology, somewhere between a laboratory machine (very good but very slow) and the commodity-scale behemoths (fast but careless) to enable us to put only clean whole grains into the Zentrofan mill. Anything much larger than a grain will block the input and slow down or halt milling.
        The Zentrofan produces wholemeal flour and we don’t sift it after milling. We figure that there’s not a lot of point working hard to find and grow grain with more nutrients in only to remove them before selling the flour to our customers (because most of the minerals and vitamins are located in the bran layers of the grain).
        The cost (in 2016) of the basic mill was about £7k and we have spent quite a bit more rigging up a larger hopper (it comes with a 25kg input) so that we can mill up to 120 kg unattended overnight (as long as no beans block the input!). One thing that is often overlooked in assessing the cost of a mill is the energy input. The Zentrofan produces 15-20 kg per hour but its 1.5 kW motor draws less than 2 amps while running. The considerable extra friction of a conventional stone mill probably indicates a higher energy input per kg of wholemeal milled (the heat of the flour is a bit of a give-away). Big roller mills guzzle energy in de-constructing the wheat grain into its constituent parts to make refined white flour that, under UK law, is deemed so nutritionally depleted that four synthetic nutrients have to be added back (two B vitamins, iron and chalk, i.e. calcium). Putting all these considerations together, we think the Zentrofan cyclone mill is the best way to process grain into fine flour. If people want something lighter than wholemeal, I suggest that they sift the coarse bran out, ferment it separately (generating nutritious compounds and softening the bran) and re-incorporate it into the bread after making the dough with the lighter flour fraction. Zero-waste + maximum digestible fibre and great flavour.

        • Seth says:

          Looking at the Zentrofan as a viable option for my milling needs, I appreciate the above information.
          If you wouldn’t mind, could you tell me the ability for the Zentrofan to produce a flour that would be suitable for sifting (to a T80-110). Although I want to continue using more whole-gran flour, it would be nice to have the flexibility.
          Thanks in advance,

          • Scotland The Bread says:

            Hello, Seth. You could certainly sift the wholemeal flour from the Zentrofan to produce a ‘brown’ or ‘85%’ extraction flour, as UK millers would understand T80-110. (For a discussion of the varying terms for flour, from ’00’ to ‘1740’ etc) see page 78 of my book Bread Matters.) The only possible downside is that the Zentrofan reduces both the bran and the endosperm (the white flour) to a very fine particle size, so you might need a fairly fine sieve to remove the 10-15% of bigger bran particles that will result in the flour grade you are aiming for. But it is very doable. Best wishes, Andrew.

        • Marla M Nelson says:

          Any thought on sprouting the grains dehydrating( to increase digestibility ) then grinding ? I wish this kind of milling was available in the USA !

          • Scotland The Bread says:

            Yes, Marla. We are hoping to do this with some of our grains next year. There is no doubt that sprouted grains are more digestible and nutritious than unsprouted ones. The only question is, how to manage a proportion of sprouted grain flour in an ordinary loaf. You can’t make bread entirely with sprouted flour because the amylase and the available sugars tend to produce a very sticky loaf. But using a nice acidic sourdough certainly helps.

  3. Jonny Muir says:

    Thanks Andrew, that is really helpful and I appreciate your time.

    I do have a couple of really quick questions that would help me out. Could I direct message you? I am @jonnymoo on twitter.

    • Jonny Muir says:

      Ignore my last comment – your answer to Emma was exactly what I was going to ask! Just wanted some cost indications. Don’t know why I thought it should be a closed conversation, how very English of me!

      Emma – you sound like you are investigating the same thing as me. Good luck, and I loved the Farmerama cereal postcasts. It would be interesting to know if anyone is looking at similar tech to Zentrofan, it sounds very promising. The Dyson of mills.

      • Emma says:

        haha – I am obviously too blunt. Definitely super interesting but agree with Andrew above about the cleaning. Good luck!

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