Innovations in wheat cleaning

by Mark Fowler
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The process of converting wheat into flour has three fundamental steps — wheat cleaning, wheat conditioning, and of course, the milling process. All three steps impact the profitability and efficiency of the mill.

However, the impact of the wheat cleaning process, with regards to flour quality and profitability, is commonly underestimated. Elements of the cleaning process that impact profitability include minimizing the loss of quality wheat into the screenings and cost of operating and maintaining equipment in the cleaning process.

The production of quality flour begins with effective wheat cleaning. Critical flour quality characteristics, such as ash and color, are impacted by the cleanliness of the wheat delivered to the first break rolls.

Consistency in the wheat tempering and conditioning process depends on effectively removing dust, foreign grains and other impurities from the wheat. The flour milling industry continues to develop and incorporate new technology to improve flour quality and consistency, maximize equipment utilization by reducing downtime and improve energy utilization.

Recent advances in the process to remove the unwanted impurities from the quality wheat reflect the industry’s desire to become more efficient at producing a consistent, quality product.

Improving the Basics

Screening or sieving to separate good quality wheat from foreign grains, sand, stones and many other types of course and fine impurities has been the principal method of cleaning wheat from the beginning of flour milling history.

Over time, various machines have been introduced and improved upon to increase sieving efficiencies. Sifters and sifting reels to remove impurities and classify wheat by size were commonly used as primary cleaning equipment as the importance of cleaning and grading grain developed.

As the operating capacities of mills increased, the use of oscillating or vibratory screeners expanded to keep up with the increased capacity requirements. Aspiration was incorporated into these designs to remove the dust and light impurities before the screening to improve effectiveness of the sieving as well.

As grain cleaning technology continued to advance, machines that combined multiple cleaning principles were introduced incorporating sieving, density separation and aspiration into one machine. Combination machines allowed more wheat cleaning capacity to be done in a smaller space, helping to reduce the capital cost of new mills and mill expansions. New innovations in wheat cleaning reintroduce the advantages of sifting and grading wheat by size while removing impurities. These more recent advancements in wheat cleaning integrate modern technology and materials to meet the growing demand for higher operating capacity, improved cleaning efficiency and lowering the cost of operation and maintenance.

Wheat scouring is another traditional cleaning principle that evolved and advanced with technology. Early applications of wheat scouring can be connected to wheat washing to remove dirt, sand and stones from the quality wheat.

Wheat washing transitioned into dry scouring with the purpose of removing the dust and fine dirt particles attached to the outer surface of the wheat kernel, especially the dirt trapped in the crease of the wheat kernel. Further advancement of the wheat scouring process resulted in intensive scouring to de-bran or peel the outer layers of the bran coat from the wheat kernel without grinding or breaking the wheat kernel.

Advances in Color Sorting

The first application of color sorting in grain processing can be traced back to rice milling. Color sorting was first adopted in the wheat milling industry by durum processers looking for an effective method of removing ergot contaminated wheat to produce a safer, cleaner product. The first generation of color sorters were monochromatic, sorting grain-based shades of black and white.

Advances in technology incorporated the use of high-resolution bichromatic cameras in addition to the standard monochromatic cameras for inspection in a wider color spectrum. This allowed the detection of more subtle defects and impurities.

There are several companies introducing innovative machines categorized as color or optical sorters. However, these machines go beyond the optical separation of unwanted impurities by color. Recent advancements incorporate infrared and even ultraviolet sorting capabilities combined with color detection technology to enable the inspection for foreign material with invisible optical properties, such as clear glass and stones.

Improvements in optical sorting go beyond the cameras detecting the defects. Better light intensity using fluorescent or halogen lighting contributes to more accurate separation of impurities from quality wheat. High-speed, reliable ejectors enable improved precision in the discharge and removal of defects once they are detected. Better distribution and uniformity of the feeders regulating the wheat into the machines have aided in increasing operating capacities.

These recent innovations have increased the capacity and productivity of optical sorters. Advances in technology have reduced the price per tonne to purchase and operate improving the cost effectiveness of optical sorters. The result is a much wider application of optical sorting in wheat milling. The ability to detect and separate on the basis of color, size and shape with remarkable accuracy within a split second has optical sorters taking the place of more traditional disc and indent separators.

Optical sorters reduce the loss of quality wheat as compared to using mechanical shape separation. This improved precision, coupled with the higher cost of wheat, has increased the cost-effectiveness of optical technology displacing traditional cleaners in new installations.

Applied Solutions

These individual advancements in wheat cleaning technology are irrelevant unless effectively incorporated into cleaning systems. The wheat cleaning process in modern flour milling focuses on more than a single machine. The changing characteristics of wheat from season to season at times require immediate adjustments. Identifying those factors is important to keep up with customer requirements and the increasing cost of wheat. Two challenges that are of continuous concern to millers are wheat kernel size and fusarium contamination.

Kernel size impacts all classes and origin of wheat. Kernel size is affected by wheat type and growing conditions. As cost of wheat continues to increase, millers are blending wheat of different classes and origins to minimize cost and meet customer requirements. Blending of wheat classes can cause challenges in the wheat cleaning process by increasing the range of size and density of quality wheat. The application of optical sorting rather than mechanical sorting allows the operator to more quickly adjust the cleaning system to reduce the loss of quality wheat due to these subtle differences in size and density.

Fusarium contamination is most commonly associated with soft wheat or spring wheat, but can affect all types of wheat. Fusarium cannot be removed from individual wheat kernels. Fusarium reduces the density of wheat as well as giving the kernels a slightly pink tint.

Innovations in optical sorting have effectively removed fusarium-affected wheat from quality wheat. This can allow the miller to recover a portion of quality wheat from fusarium contaminated wheat.

More traditional applications of new innovations in wheat cleaning include reduced energy consumption and lower maintenance costs. Reducing the amount of moving parts increases the durability and reduces downtime and maintenance cost of cleaning wheat.

Consolidating multiple machines using traditional mechanical methods of removing impurities from wheat based on size, shape and density into one optical sorter reduces energy cost.

Consistent performance, improved monitoring capabilities and better precision of removal of impurities minimizes loss of quality wheat during the cleaning process. Minimized loss of quality wheat equates to maximizing extraction and flour yields improving profitability.

But in the end, applying these new innovations in the cleaning process produces a better quality, safer, more consistent finished product for the customer. This results in improving the profitability and image of our industry at a time when product purity and food safety standards are of the utmost importance.