Since the third century B.C., the process of milling grains into flour consisted of passing whole grains through two large moving millstones. Traditionally, one of the stones turned (the runner stone) via water, animal or human power source, while the other (the bed stone) remained stationary. This method crushes the grains but keeps all the parts of the grain (the germ, bran and endosperm) intact. Millstones grind at a slow rate, so the friction only produces a low heat, which keeps the germ fat from oxidizing and becoming rancid, which can destroy some of the nutrients inherent in the grain.
Stone milling was the norm throughout history until around the 19th century. As times and cooking practices changed, it was found that stone milling didn’t produce flour that was fine enough for making pastries. Some such concerns, plus the growing demand for flour vs. the slow production time of stone mills, led to the development of a faster alternative to stone milling, called roller milling.
The roller milling, or “high grinding” method slowly replaced most existing traditional stone mills. With roller milling, steel rollers quickly explode the grain over a series of passes through the mill. The reground flour is thoroughly sifted to remove the bran and germ, thereby also removing some of the nutrients. The friction of the roller milling process also produces higher temperature flour, which is reported to affect the nutrients as well. According to a publication by the Ecological Agriculture Projects, “heat causes the fat from the germ portion to oxidize and become rancid and much of the vitamins to be destroyed” (Aubert, 1989, http://eap.mcgill.ca/publications/EAP35.htm). Similarly, the Flour Milling, Baking and Confectionery Technology Department at the Central Food Technological Research Institute found that some loss of essential fatty acid and amino acids occurs at milling temperatures above 170°F.
The roller milling process produces flour that is whiter than traditional dark-colored, nutrient-rich, stone ground flour. Upon its introduction, the lighter color appealed to consumers, particularly the wealthy, and so white flour became desirable to all, even though it was less nutritious. With its ability to be produced faster in order to meet growing consumer demand, white flour eventually dominated the market.
Certainly, millers knew that nutrients were being lost in the process, which led to the development of enriched flour, where synthetic vitamins and minerals are added to the flour after milling. Of course, synthetic is never the same as the real thing. Which raised the question, what effect would this flour have on people’s health over time? The responses to that question called for change.
By 1950, Dr. Lee’s mill was available to consumers. Using an air current to propel grains against a stationary corundum stone, Dr. Lee’s mill was able to produce a flour fine enough for pastry, while retaining all the nutritional value of whole grains. According to Lee and other nutritionists, milling by stone, in the amount needed for immediate use, is the only way to retain the complete grain and it’s nutrients, which include dietary fiber, phosphorus, thiamin, niacin, and B6. According to an essay published by Ecological Agriculture Projects, “The nutritional importance of using fresh stone-ground grains for bread-making was revealed in the results of feeding studies in Germany (Bernasek, 1970).”
The history of stone milling is an interesting look at the economy’s effect on nutrition. Fortunately, there is now a growing movement to go back to the stone milling methods that provide people the nutrition they need.
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