The Quality of Flour
The quality of flour, and discussions thereof involve numerous physical and chemical variables and indicators. The technical aspects of a wide variety of flours have been have been covered in numerous texts and scientific papers. The more practical aspects of flour, vis-a-vis whether or not this or that flour makes a better loaf of bread are more subjective and will be discussed in another part of this treatise. The breadmaking potential of wheat is largely derived from the quantity and quality of its protein content. Genetic and environment each play important roles in determining protein quality. Protein quantity is influenced mainly by environmental factors, while the quality of the protein is genetically determined. In wheat varieties that are grown under comparable environmental conditions, a high quality wheat will produce good bread over a fairly broad range of protein levels, but a poor quality wheat will generally result in low quality bread even if the protein content is higher. For more on this topic the reader is referred to Pyler (3). In "Baking Science & Technology" Pyler also states that:
"Wheat is unique among cereals in that its milled product, flour, alone is capable of forming a dough that will retain the gas evolved during fermentation and, on baking, will yield a light, well aerated loaf of bread. This unique characteristic of wheat is derived from its proteins which, on combining with water during the mixing process, result in gluten, the actual substance that imparts the property of gas retention to dough. Because of the preeminent position that the wheat proteins occupy in baking, it is not surprising that a great deal of research has been expended on them, and it is indicative of the complexity of protein material in general that many basic questions still remain unanswered…"
The proteins in flour can be divided into two groups based upon their solubility in water. As indicated earlier, when the insoluble proteins in the flour are combined with water during the mixing process, gluten is formed. A number of noted sources describe gluten as a cohesive substance, somewhat rubbery and elastic, gray in color, with an insipid taste. Gluten is comprised of two insoluble proteins, glutenin (which is stable, and gives it its strength), and gliadin (which is soft and sticky, and gives it its elasticity). Italian law allows values of dry gluten that range from 7% in type 00 flour, to 10% in type 1, 2, and whole wheat flour. Strong flours, i.e. those with high protein content, have upwards of 13-14% dry gluten. Dry Gluten is the product of "washing" a specific amount of dough under gently running water while catching the dough pieces in a cheesecloth. A dough thus washed and prepared from 50 gr. of patent flour, 30 ml of water and 1 gr. of salt will yield about 15 grams of a cohesive, sticky and gummy substance or dough. The remaining dough consists of a moist sticky albumen (protein) which is insoluble inwater. This dough can be stretched without breaking and contracts when released. Weighing this dough, and then drying it in an oven at low temperature, results in what is termed "dry gluten". The difference in weight between the wet and dry gluten equals the absorption capacity of the gluten producing albumen. This is about one third of the weight of the original (pre-drying) dough. Of importance is the fact that the weight of the dry gluten made from 100 grams of flour equals the percentage of gluten producing albumen (protein) in the flour. Albumin is a gluten forming protein in wheat flour. In a given batch of flour about 12% of the albumen is gluten forming protein and approximately 1% is water soluble albumen. More details on this subject can be found in "Baking, The Art and Science", (6).
To continue from Baking Science & Technology (3):
"Bakers often use the terms protein and gluten interchangeably. Yet, these terms do not denote the same thing. Protein comprises all the nitrogenous substances present in flour and other food materials and is estimated by the Kjeldahl and other methods that are specific for nitrogen. Gluten, on the other hand, represents the end product obtained when a small piece of dough is worked and washed in water....
....The concepts of flour quality and flour strength are difficult to define concisely. This is largely because flour quality is expressed by a variety of chemical and physical properties of dough, none of which serves as an adequate index by itself, or is independent of other variables. Thus, different physical and chemical testing methods, different baking test procedures, and different dough processing treatments, when applied to the same flour, will yield results that may lead to widely divergent conclusions as to the flour's quality. Moreover, the end use to which a flour is to be put enters importantly into any evaluation of its quality. The marked distinction between a soft wheat cake flour, and a hard wheat bread flour is clearly recognized by most bakers. On the other hand, a baker may be less certain in distinguishing between the specifications of flour intended for the production of white pan bread as against hearth breads. This difficulty accounts for the frequently observed fact that flours purchased by bakers for specific purposes, such as bread, pastry, cracker, or biscuit production, show wide quality variations within each group…"
In addition to the physical and chemical data briefly described above, bakers need to be aware of other criteria by which to judge their flours. The information provided below has been excerpted from "Special and Decorative Breads" (2) with additional technical information adapted from the Molino Sima (8) recipe booklet, "Il Manuale del Panificatore" (5), and "Baking Science & Technology" (3).
We cannot state too strongly that providing these data regarding the chemical and physical composition of flour to commercial bakers is standard procedure in Europe and, as far as we are aware, in Canada, but not so in the US. This must be changed if the artisan bread effort in the USA is to continue to move forward.