Roller milling is a common process used to grind wheat grain into flour. The process consists of several steps:
Cleaning: The wheat is first cleaned to remove any foreign matter such as dirt, stones, or other grains. This is done using a combination of screening, aspiration, and magnets.
Conditioning: The wheat is then conditioned to improve its milling properties. This involves adding water to the wheat and allowing it to rest for several hours to soften the bran and germ. During this period, the endosperm and bran/germ expand due to osmosis at different rates due to their distinct physio-chemical structure. The endosperm become soft while bran/germ become rubbery and flaky.
Breaking: The wheat is then passed through a series of rollers that break the wheat into smaller pieces. This process separates the endosperm, bran, and germ.
Sieving: The broken wheat pieces are then sifted through a series of sieves that separate the different parts based on particle size. The largest particles are separated out as bran, while the finer particles become semolina.
Reducing: The semolina is then passed through a series of rollers that further reduce the particle size and create a finer flour.
Purifying: The flour is then passed through a series of purifiers that use air currents to remove any remaining impurities.
Bleaching: The flour may then be bleached using chemicals such as chlorine dioxide or benzoyl peroxide to whiten the flour and improve its baking properties.
Adding Additives: Flour and dough conditioners are often added to improve the flour's baking properties, such as rising, texture, and shelf life. These additives can contain synthetic chemicals, which may be harmful in large quantities.
The final product of the roller milling process is industrially milled flour, which is often bleached and treated with additives. This type of flour may have lower nutrient value and flavor compared to minimally processed artisanal stone-milled flour.
Sourdough made from roller-milled refined flour is generally high in GI (Glycemic Index) due to its high carbohydrate content and the lack of fiber and nutrients. The roller milling process removes the bran and germ, which are the parts of the wheat grain that contain fiber, vitamins, and minerals. This results in a flour that is higher in starch and lower in fiber, which can lead to a higher GI.
The GI is a measure of how quickly a food raises blood glucose levels after consumption.
Foods with a high GI are rapidly absorbed and can cause a rapid spike in blood glucose levels, which can be problematic for people with diabetes or metabolic disorders.
In contrast, sourdough bread made from whole grain flour or artisan stone-milled flour, which contain more fiber and nutrients, can have a lower GI and be more beneficial for blood sugar control.
Additionally, the sourdough fermentation process can further lower the GI by breaking down some of the carbohydrates and gluten.
Moreover, using bleached flour with additives in sourdough bread-making is not ideal for gut health because the additives may disrupt the gut microbiome. The gut microbiome is made up of trillions of microorganisms that play an essential role in maintaining digestive health, immunity, and overall well-being.
On the other hand, artisan stone-milled flour is minimally processed, retains more of the bran and germ, and can be a healthier and more sustainable option. Stone-milled flour can have a coarser, more irregular texture with varying particle sizes, which can give baked goods a more rustic, artisanal quality and result in a more complex flavor profile.
Choosing to use artisanal stone-milled flour instead of industrially produced flour can also promote more sustainable and equitable food systems by supporting small-scale farmers, millers, and local food systems.