The first problem: limited benefits from a wheat scouring

In the milling industry, optimizing flour extraction efficiency is paramount, starting from the screen room and conditioning stage, which are critical points requiring meticulous attention.

Traditionally, the primary tool utilized in the screen room for wheat cleaning is the scourer. Its role encompasses the removal of surface adherents like bristles and the reduction of ash content, along with addressing biohazard concerns such as moulds, DON (deoxynivalenol), and bacteria.

However, empirical assessments of European and U.S. wheats reveal significant shortcomings in the efficacy of Scourers. Expected benefits in ash reduction and biohazard mitigation are found to be negligible, raising questions about the viability of this approach.

The fundamental operational principle of the scourer presents an inherent limitation. While designed to enhance efficiency by subjecting wheat kernels to vigorous beaters against a corrugated screen, microscopic analysis reveals a persistent bond between surface impurities and the wheat kernel, rendering complete removal via mechanical agitation unfeasible.

This inefficacy exacerbates challenges during conditioning. Mineral residues, when hydrated, become more resistant to removal, while residual bio-organisms foster an environment conducive to foul odours, further complicating operations.

Consequently, these inefficiencies lead to tangible losses in flour extraction yield and product shelf life. 

Addressing these challenges requires a nuanced approach that reassesses the role of Scourers, enhances conditioning methodologies, and explores innovative solutions to optimize flour extraction efficiency while preserving product quality and shelf life.

The second problem: addition of extra water to compensate for milling loss

In conventional milling processes, a customary challenge arises in the form of a phenomenon known as, milling loss, where approximately 2% of wheat moisture is typically lost. This issue stems from the inadequate penetration of water into the innermost region of the wheat, specifically the endosperm core. 

The solution 

Omas Industries S.r.l., a distinguished Italian milling equipment supplier, initiated this study to evaluate the performance of Scourers on European and United States wheat varieties. The assessment involved analysing the scourer performance based on weight and the chemical and biohazard composition of the wheat. Subsequently, the study investigated the efficacy of vertical abrasion as an alternative method to traditional scouring. Previous attempts at vertical abrasion were limited to wet wheat post-conditioning. However, our research revealed that water introduction during conditioning improved the bond between impurities and wheat kernels, fostering a favourable environment for biohazardous organisms.

In response to these findings, Omas introduced “Dante - The Flour Extraction Booster”, a specialized vertical abrasion system designed for dry wheat. Dante employs Dry Wheat Scrubbing (DST) to eliminate surface adhered impurities and biohazardous organisms. The principle behind Dante involves gently scrubbing wheat within a controlled ventilation system using a vertical array of stones and a specially designed screen.

Wheat, being a fruit type, possesses a pericarp layer with high water resistance properties. By employing DST to scratch the surface of this layer, water ingress becomes quicker, deeper, and more effective. 

The implementation of DST reduces conditioning time by over 25%, albeit resulting in higher water absorption by the wheat. This time-saving benefit enables swift transfer of conditioned wheat to the mill, consequently enhancing total mill capacity.

Moreover, the enhanced water penetration into the wheat kernel reaches the core of the endosperm, thereby reducing milling loss and necessitating 1% less water absorption during conditioning. Figure 2 illustrates the comparison of water retention between standard wheat, wheat processed by a scourer, and wheat processed by DST, highlighting significantly higher water retention in the DST process. Further analysis, always in Figure 2, showcases the ash reduction comparison between a scourer and DST, providing a concise overview for easier comprehension. Finally, a field study involving the ash curve (Figure 2) conducted on French wheat corroborated that simply replacing Scourers with DST in any flour mill enabled the inclusion of extra passages in the final flour stream, resulting in extracting up to 1% more flour with the same ash content.

Figure 2. H2O Evaporation and Ash Reduction 

A comparison of the process flow between traditional conditioning with wet peeler and DST (Figure 3) demonstrates the benefits of the latter.

Figure 3. Conditioning Flow Diagram with wet peeling VS Dante Flour Extraction Booster

 

In this extraction process, known as door-to-door extraction, the system removes 0.5% to 1% of wheat dust before milling, which is subsequently added to the byproducts after milling, ensuring no loss of product.

Additionally, it is noteworthy that beyond the advantages conferred upon the milling process, Dry Wheat Scrubbing (DST) has demonstrated a remarkable capacity for reducing bio-hazardous organisms. By subjecting wheat to DST, an impressive 85% decrease in mould presence and a substantial 75% reduction in bacteria (see Figure 4) have been achieved. 

Furthermore, DST has shown promise in diminishing the levels of herbicides and pesticides, with an approximate 30% reduction recorded. These findings underscore the pivotal role of DST in not only optimizing flour extraction efficiency but also in fortifying food safety and quality standards within the milling industry. Through its ability to significantly mitigate health risks associated with microbial contaminants and agricultural chemicals, DST emerges as a valuable tool for ensuring the production of safer and higher-quality flour. The data of wheat processed on Scourer and DST was tested by an independent lab and showed immense improvement on the removal of surface adhered impurities and reduction in ash content, Mycotoxins and Vomitoxins (DON) before conditioning.

Figure 4. Mould and bacterial reduction

In conclusion, the implementation of Dry Wheat Scrubbing (DST) presents substantial advantages over traditional scouring methods. Integrating DST into any flour mill operation not only enhances sustainability but also augments flexibility and resilience in the milling process. The DST system boasts lower energy consumption per tonne, increased flour production, and notable enhancements in the shelf life and quality of the produced flour. 

Figure 5, a typical site installation of DST in a flour mill’s screen room showcases its practical application. For further inquiries or information, please don't hesitate to contact the dedicated teams at Omas.

Figure 5. Site installation of Dante Flour Extraction Booster