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4 rheology terms you must know to understand specialty wheat flour

It is a must to get your fundamentals right before you dive into the big wide world of baking with specialty wheat flour. Since most of you are exposed to these terms via instagram, or via using imported flour, or via just reading, this brief compilation on the most important ones, will help you navigate through how different countries put out their flour categories, and how you can compare them.


Ash Content:


Ash content is used to determine the quality and purity of a given flour. To define what is ash - it is the amount of minerals which are left after a flour is burnt in a lab test, basically the non-combustible part.


The total ash content of whole wheat flour varies from 1.2% to 2.9% based on the species and the variety.


This ash is made of minerals like Phosphorus, Potassium, Magnesium, Calcium, Zinc Iron and Copper. Higher ash content in a flour means more bran, germ, and outer endosperm in the flour.


Lower ash content means that the flour is more refined. The pure endosperm which makes up for over 80% of the wheat kernel contains only about 0.35% ash content.


A higher endosperm ash content is usually associated with higher dietary fiber, vitamins and non-gluten protein in the wheat kernel.


Moisture:


Moisture is one of the most important components at play when it comes to flour storage. Generally in milling, it is desirable to maintain a moisture percentage below 14% to avoid activating the entire microcosm of life which leads to flour fermentation.


Stoneground flour usually has a moisture content below 10% and suited for storage upto 4 months under dark, cool, and dry conditions. On the other hand, when we talk about commercial milling, i.e. using roller mills, the wheat grains are first hydrated to 15-17% by adding water, which helps harden the bran and the germ, and eventually get separated easily to make all purpose flour (maida) with the endosperm.


Higher the level of moisture in the end product (all purpose flour or maida), faster the flour will start fermenting and get spoiled during the storage period.


However, as an industry practice, roller millers try to keep it as high as they possibly can (taking in account the trade off) to get a higher flour yield / weight from a given amount of wheat grain weight.


The method to calculate moisture is called ‘air-oven’, i.e. a 2g sample of flour is heated for an hour at 266°F and the loss in weight is taken as the moisture content.


Protein:


Wheat has 4 proteins namely: Albumin, Globulin, Prolamin, and Glutelin (aka Gluten). Gluten makes up for over 80% of the wheat’s protein. It affects a lot of rheological properties of the dough: extensibility and elasticity, most importantly.


However, given the complex structure of the wheat genome (complete set of genetic information in an organism), it is not possible to measure protein percentage directly by any tests. Rather, in case of wheat, as per Dumas Combustion Procedure: Nitrogen * 5.7 = Protein.


That does not mean that at farming level one can keep increasing the nitrogen supply to the plant to achieve maximum protein. Genetically a specific wheat variety can only have a set percentage of maximum protein, and once that is achieved, additional nitrogen input will decrease the wheat grain yield. Most fertilizers today exist in the form of Amide, Ammoniacal or Nitrate compounds of Nitrogen and react differently with the plant and the soil when applied.


Thus, it is imperative that one understands that it is a complex process to grow quality wheat grains, make quality flour without any additives and baked craft products like sourdough, croissants and so on. Adding substances like vital gluten can only add to the quantity of protein, but not the quality in the dough, and has its own health implications.


Damaged Starch:


Starch is a complex carbohydrate polymer, made from simple sugar glucose. It is made of two parts: AMYLOSE and AMYLOPECTIN. It makes up to 67-68% of whole wheat and 78-82% of whole wheat flour. Normally, starch absorbs only 0.3x-0.4x water of its weight, whereas DAMAGED starch can absorb 3x-4x water of its weight.


Hard wheat has a higher starch damage of upto 6-9% as it takes more energy than soft wheat to break its protein-starch matrix in the endosperm. That is also to say that hard wheats have a higher water holding capacity.


Now, damaged starch is attacked by these enzymes called AMYLASE (not to be confused with AMYLOSE) during dough making.


Alpha and Beta Amylase both are responsible for converting starch into simple sugars. These sugars in turn serve as food for the yeast in the dough. This whole process happens in tandem with gluten network formation.


To learn further about the extent of this enzyme activity, there is a test value called FALLING NUMBER, which is measured by making a flour-water paste, stirring it, and letting it fall to the bottom of the test tube. Essentially, to know about the stability of structural integrity of starch chains and dough viscosity.


Bakery flours for breads usually have 250-300 seconds as their falling number.


We hope this was helpful, and has left with you some answers, and more questions about all things wheat. If you have further questions and would love to know anything in specific, please carry on the discussion on our discord channel in #nutritionaandrheology thread.