World Grain Book Review: Wheat Flour Milling
September 01, 1997
by Teresa Acklin
Flour milling text is first of its kind in almost a half century.
By Neil Sosland
Something truly extraordinary has taken place with the publication of Elieser Posner and Arthur Hibbs' Wheat Flour Milling. This is the first conventional text of note on operative flour milling published in English-speaking countries since the 1960s. It is the first milling book written primarily for North American flour milling and those who follow this style worldwide since early in the century; however, the book also contains considerable material on European milling as well.
Indeed, it is the first American milling publication since B. Dedrick, Practical Milling, published in 1924. Of course, since that that time, we have had J. F. Lockwood's Flour Milling, published in 1946; L. Smith's Flour Milling Technology, out in 1948; and J.H. Scott's Flour Milling Process, out in 1951. We also have had a ongoing series of publications issued by the Association of Operative Millers, including the Cereal Millers Handbook and of course the various A.O.M. correspondence courses during the intervening years.
Although the book has been published by the American Association of Cereal Chemists, this is a miller's book, written by millers primarily for those engaged in milling and those who have a direct interest in that industry.
In fact, it contains very little chemistry, only small amounts of milling history and, perhaps some will conclude, not enough about the computer, automation or those other subjects which have grabbed the headlines in recent decades. This is a “meat and potato” millers book, but with few exceptions one that is very readable both for a non-miller as well as for an operative.
While adhering to a tight, traditional format in covering their subject matter, the authors have clearly outlined the present and future role of technology, including the computer and even automation, giving the subject the perspective it correctly requires to understand both milling's present and future opportunities in this area.
It adequately reviews the extensive list of technological breakthroughs the industry has enjoyed over the past half century since the most recent milling texts were published, showing their impact on current milling. Because of the breadth of subject matter covered, the book should prove of great value to most wheat flour millers whether in developing or developed nations.
The authors come to their task with excellent credentials. Elieser S. Posner, who began his milling career in Israel, was for many years a professor of milling at Kansas State University, Manhattan, Kansas, U.S. Arthur N. Hibbs was before his retirement superintendent for the former International Milling Co. and one of the veteran figures in U.S. flour milling.The Art of Flour Milling
In the preface, the authors open their subject by pointing out “flour milling is considered an art.”
“The miller applies experience accumulated over many generations. In the past, the art of milling was learned through apprentice programs. Formal schooling in milling didn't exist until the 19th century. Even today, the miller still subjectively adjusts the steps of the process, such as the intensity of grinding, the flow of the sifter separations and the air and sieves in the purifiers. Today, however, other disciplines mechanical, chemical and administration are also used. The miller of the future will be an expert in a very unique field that depends on information and knowledge of several different disciplines.”
They explain that the objective of the milling process is to manufacture flour as efficiently as possible, technically and economically.
“This involves purchasing, testing, storing, preparing, milling, blending of flours, packaging, loading and shipping. The miller must adjust the operation to local conditions and demands in each of these stages.
“Research and development of wheat flour milling machinery and techniques are ongoing processes. Although we seldom observe sudden breakthroughs, changes are continuously tested, criticized, improved and accepted. This has been the history of milling and baking since the first attempts of the Egyptians to crush selected seeds and develop the leavening process of dough before baking.
“This book could not cover all aspects of the technology and economics of wheat flour milling and all the methods developed in the past. Our objective is to inform the reader about many important segments of the milling process. We would like the book to stimulate the reader to look beyond it to the references and additional readings suggested.”
Each chapter at the end contains extensive suggested reading lists.
The point is made in the first chapter, “Wheat: The Raw Material,” that there are more than 500 wheat varieties available in the United States where a wheat breeder can certify a new wheat variety and sell it on the market. This contrasts with some countries, such as Canada, where the number of wheat varieties on the market is fixed.
Summarizing the milling process in the first chapter, the authors state, “in the classical milling process, using rolls to separate the endosperm from the bran, the miller has an interest in minimal abrasion or damage to the bran layers. The goal is to keep the bran as whole as possible and in its original thickness, so that certain spots are not weakened and likely to split during milling.”Operations and Technology
Early in the book under “Wheat Sampling,” the authors acknowledge one of the greatest challenges of a modern milling operation is the rapid evaluation of incoming wheat “so that the wheat can be directed to the appropriate bin.” Reviewing wheat grading and quality characteristics such as protein and flour yield, they note that the behavior of different sizes of wheat kernels in the milling process has been studied to examine the influences of kernel size on water absorption during tempering and during actual milling. The authors add that uniformity of wheat kernel size plays an important role in milling stability.
In analyzing protein, they acknowledge the usefulness of both the traditional chemical test and near-infrared reflectance analysis, merely noting here that “near-infrared reflectance analysis of wheat has been developed as a means for fast protein quantitation.”
“Experimental and Laboratory Milling” is another subject covered early in the book. Experimental milling is summarized as “to simulate the milling process in a practical way with a small wheat sample to provide technical information about the raw material and the functionality of the end product.”
The authors note that “with the availability of the desktop or personal computer, many possibilities are open to the laboratory technician and miller in data collection and use,” adding “wheat quality data can be used with the appropriate software programs to evaluate the milling quality potential and also the effect it has on the economic return from the milling operation. In the future, experimental mills will likely assume greater importance in the control of large commercial milling units.”
Under “Storage and Blending,” the authors stress “knowledge and understanding of wheat grading and specification methods ensures receipt of good quality wheat with below-maximum level of impurities and results in the most economic value. Wheat millability and compatibility with other wheat varieties in the blend are other concerns of the miller in specifying wheat quality.”
They especially stress “blending of wheat is a must in modern times when millers must accommodate their customers by producing a large number of special flours.” There is no procedure to determine an optimum blending ratio that can predict accurately the mill mix and the resulting flours, they add.
“Blending models currently provide procedures for responding to price and technology changes. Thus, it is possible to have readily available not only quality schedules but also price and quantity schedules within the model's framework, to analyze purchase and sale of wheats and products.”
A chapter on “Wheat Cleaning House and Conditioning for Milling” warns that material separated in the cleaning house from the millable wheat could be poisonous, reduce flour quality or damage machinery. Moving on to wheat tempering, they add “an old slogan of the experienced miller is that having clean, consistent, well-prepared wheat at the first grinding stage is at least half the battle toward mill balance, which results in the most favorable flour extraction and flour quality.”
The point is also made here that “the relative readiness of the kernel is unique to every wheat and mill.” Tempering then involves adding cold or warm water to the wheat and allowing the wheat to rest in bins until it reaches the optimum moisture distribution and kernel suitability for milling. “The objective is to toughen the bran and to mellow the endosperm,” they emphasize. The authors also point out that one of the main goals in wheat tempering before milling is to distribute the water uniformly in all the kernels of wheat mix. Even with the best dispersion of water in the bulk of commercial wheat, water penetrates into the large and the small kernels in the mix to different degrees, they stress. Various means for shortening tempering are examined.
The grinding process is the most important step in the milling system, the authors say at the start of the chapter on this subject. In the grinding operation, energy is expended to break apart the bran and endosperm and reduce the endosperm to flour, they note.
Engineering concepts and formulas are incorporated into the analysis of the roller mill. The differences between the U.S. and European technology is explained in clear detail, and while numerous details are covered, the material in general is clear even to the non-miller, a real challenge because of the inherent complexities of this area. An explanation of the prebreak operation also is one of the book's many strong points.
At the end of this chapter, the authors again discuss future trends in the industry.
“The new mills will be designed to reduce labor and machinery to lower capital and manufacturing costs. The roller mill will continue to be the basic grinder but will be supplemented by more auxiliary machines to reduce the number of rolls. Increased use will be made of impact and debranning machines in combination with rolls to reduce the number of process steps.”
They also acknowledge that compact mills are a growing trend for specialty flour markets.
“The Sieving Process,” always a challenging subject for non-millers, is clearly explained. Focusing on future changes, they predict “in the mill, gyrating sifters have become larger to save space and reduce cost. The present size, eight sections, is believed to be the economic limit in size.
“It may be possible to separate and remove flour in the pneumatic lift collectors to save space and sifters....Air classifiers and electrostatic separators for use in the milling process have proven to be expensive. The present sifters are considered inefficient because often the first two or three sieves separate most of the fraction while the remaining sieves remove very little. Future improvements in sifting efficiency may come from a better understanding of the sieving process. It may be necessary to divide the material into smaller streams and change the flow configuration of the sieves to improve sieving efficiency.”
Since much has been written in recent years that purification was on its way out of the modern mill, the subject assumed special significance. The authors do acknowledge that in recent years the role of purifiers in the mill flow diagram has diminished as millers have evaluated their cost effectiveness. They are not desirable features for a computer-controlled, compact mill requiring personnel supervision only during the day. They are most easily eliminated in soft wheat mills, somewhat less in hard winter and are still very essential in durum milling.Mill Management
Also likely to draw attention is a chapter specifically devoted to “Mill Management and Process Control.” A key part of the chapter defines the role of the head miller.
“Flour milling is continuously changing into a technology relating different disciplines of science,” they emphasize. “Computer programming, chemistry, mechanical engineering, fluid mechanics, powder technology, and economics are only some of the areas about which the miller needs information. The head miller needs good experience in the operation of a mill, because at present not all variables related to the raw material, machine configuration, and adjustments can be defined quantitatively.”
Reviewing financial management and process control, the authors underscore that the miller “must have the means to simultaneously control the whole operating system and make the right technical, economic, and management decisions.
“Optimum extraction rate is the major objective of the miller's efforts, in addition to the quality of the finished products and capacity of the mill,” they add.
For automation, they stress that “we must differentiate between directing and adjustment.
“Directing stocks, machinery, and goods is related to sending a material one way or the other, stopping or starting the flow of material, or starting a machine in a sequence. Adjustment relates to grinding rolls to achieve a certain level of grinding.
“To achieve automation, it is necessary to sense and measure the quantity and quality of the material in the process flow.”
The authors predict that artificial intelligence or an “expert system” is the approach that will elevate automation in the milling industry to its next level. Common sense, human thinking patterns and reasoned judgments must eventually be incorporated in a mill expert system, which makes decisions after scanning a large number of “if” statements and “rules” of action.
“Flour Handling and Blending” includes material on quality control and analysis, as well as infestation and pest control. Air classification and fine grinding also are incorporated at this point. The authors note the main objective of air classification is to shift the protein of a flour to make two fractions, one of which is richer in starch and the other in protein.
Various approaches to fine grinding to minimize starch damage and loss of quality also are covered. A separate section on enrichment and ingredients also is included.
The book features a separate chapter on “Milling of Soft and Durum Wheats.” Differences in processing these wheats receive thorough attention.
“Air in the Flour Milling Industry” is featured late in the book. “The miller in the modern mill regards the air-handling system as one of the more important portions of the milling operation. It is one of the controllable elements that millers can use to their advantage.”
The final chapter is on “Mill Maintenance” with the authors noting that “the key to efficient maintenance is good management of the resources invested in this activity.”
A glossary of flour milling terms and index completes the text.
This book offers a wealth of knowledge on the milling process and the required skills of the miller. Despite some fairly technical sections, it is a book both for operatives and for management personnel, even those without a technical education. The library of anyone connected with flour milling will be enriched by this book's addition.
Neil Sosland is vice-chairman, Sosland Companies, Inc., and the former editor of World Grain.