Milling the perfect flour

What is a perfect flour? It depends. When it comes to defining flour quality, there is no single set of quality characteristics that meet all needs for all end products for which flour is an important ingredient. Flour is both a functional and nutritional ingredient. The necessary flour characteristics and performance are dictated by the intended end-use. It is therefore critical that flour millers measure both sets of traits to make certain the flour will perform its intended function.

Measuring flour quality … um … characteristics

The composition of flour very much affects performance. Hard wheat, high protein flours are generally used for bread and leavened products. The strong gluten helps provide structure and stability. Soft wheat, low protein flours are generally used for cakes, cookies, crackers, noodles and some flat breads. But if it were only so simple … knowing protein quantity – while important – is simply not enough. There are many additional factors which affect flour usage and performance. Some of these affect flour’s gluten and others the starch. There are many tests, analyzers, and techniques to elucidate flour properties. However, it all starts with the wheat.

Monitoring and Controlling Wheat at In-take

Wheat comes in many varieties – each with differing characteristics. Additionally, the climate to which the wheat is subjected alters its characteristics so there can be significant variation from one crop year to another. Millers often contract with suppliers (farmers or large elevators) to deliver wheat with specific properties. It is important for the milling company to control its wheat supply and monitor it throughout the process chain. While receiving off-spec wheat does not necessarily lead to issues in the mill, receiving off-spec wheat and not knowing it can lead to production of non-performing flour. There are several important wheat specifications including moisture, hectoliter weight, protein, Falling Number, hardness, and gluten content.

When it rains at harvest, wheat can sprout. When it sprouts an enzyme called alpha-amylase is formed. Alpha-amylase breaks starches into their component sugars when flour has been mixed with water into dough. Too much enzyme can then cause real issues at bakeries and other end users. The Falling Number method was designed to detect sprout damage and measure alpha-amylase activity in wheat and flour. At mills, it is used to screen incoming grain to keep unknown sprouted grain from entering the mill, blending to meet optimal activity level, and for analyzing flour to ensure it meets specifications. It is important to note that alpha-amylase is not linear in its activity. Small changes in the amount of available enzyme can have severe consequences at the bakery. Millers monitor Falling Number very closely. There are ICC, ISO, and AACCI approved instruments and methods which help ensure the accuracy and precision of the Falling Number test. Perten Instruments offer the only validated instruments for these Falling Number Approved Methods and the new Falling Number® 1000 model is the fastest, safest and easiest to use Falling Number instrument ever.

Gluten content and quality are key characteristics and need to be tested. The traditional method for determining gluten quantity was handwashing. This has been replaced by the Perten Glutomatic System which is an internationally approved automated gluten washing method, with much better reproducibility and repeatability. While gluten quantity is important, it alone is not sufficient to predict end-use suitability as flours with the same gluten quantity may still behave differently due to differences in gluten quality. Measurements like the Gluten Index parameter achieved from the Glutomatic System at the same time as gluten content is measured provide additional information which is highly useful for the miller and ultimately the baker.

Moisture is always determined as wheat is sold either on a dry matter basis, or constant moisture content basis. Wheat is commonly bought and sold on protein content so measurement is critical to milling companies to ensure they get what they pay for. Small inaccuracies can cost the milling company large amounts of money since wheat is purchased in bulk. Hectoliter weight is essentially a density measurement and provides an indication of mill yield by volume.

Moisture and protein are typically measured with near-infrared instruments (NIR). NIR replaces old oven and wet chemical methods providing results in less than a minute. Perten newer NIR instruments Inframatic 9500 and DA 7250 are nearly as accurate as the reference methods with the added benefit of being much faster, safer, and simpler to use. In addition to moisture and protein NIR instruments can give estimates for gluten and additional parameters, and the IM 9500 NIR instrument can be equipped with a hectoliter weight module. The speed allows mills to perform many more measurements thereby better controlling and optimizing the mill. Instruments are often placed in the scale house allowing mills to test and even bin wheat according to end-use.

NIR technology can also be used for real-time measurements in-line, to blend wheat to a consistent protein content to help the mill run efficiently by reducing the number of mill modifications required at changeover. The In-line NIR DA 7300 can be permanently installed in pipes or chutes, constantly measuring characteristics as moisture and protein as the wheat flows. It can also be connected to control systems for automation.AM 5200-A Grain Moisture Meter

New high frequency grain moisture meters like the Perten Aquamatic 5200 are being used to monitor the temper process to obtain optimal flour release. These new meters are based on two recent developments – the Unified Grain Moisture Algorithm (UGMA) and identification and use of an optimal frequency of 149MHz.

Optimizing Mill Performance with Measurements

The milling process requires constant monitoring – especially at grain change overs. In-process NIR instruments allow millers to blend grain to a specific targeted protein while other instruments monitor flour properties. The in-process DA 7300 instrument provide real-time streaming results for moisture, ash and protein allowing millers to readily blend flour streams to meet specifications. The DA 7300 Diode Array Sanitary Design for MSC, Meat, Poultry, and Dairy Analysismeasurement of ash in particular is a key indicator of yield and is the parameter most often optimized. A reduction of ash variation can produce many extra tons of flour in a year thereby paying for instrument costs in a relatively short period of time. After payoff, the gains go directly to the bottom line. The DA 7300 in-process system also incorporates a built-in camera which measures specks. This allows millers to detect broken sieves as soon as they happen thereby eliminating wasted production time. At-line and lab based systems perform similar functions – just not in the process. However, the instruments are more versatile as they can often analyze whole wheat, flour, and even bake mixes.

Falling Number and gluten testing needs to be performed also on the finished flour, to verify the quality before shipping to customers. In addition several rheological measurements are commonly performed, such as water absorption, dough development time, mixing tolerance, stability and others. Changes in these characteristics will have an impact on how the flour behaves in the bakery, so it’s important to maintain consistency over time. The traditional method for determining these parameters takes about 20 minutes to perform. The new AACCI approved method 54-70.01, High-Speed Mixing Rheology of Wheat Flour Using the doughLAB, is twice as fast, measures at higher RPMs which more closely emulates today’s commercial dough mixers, and more readily resolves the development peak. These rheological measurements are used to monitor flour produced and prior to load-out. The results on flours and streams can be “virtually” blended using the doughLAB software. This allows millers to create flour with the necessary properties without having to run tests on every potential blend.

Milling flour is a complex process. It continues to evolve despite the fact that it is one of humanities’ most ancient endeavors. There are many recent developments and useful tools that help millers optimize grain purchasing, milling, and ensure that their customers receive a flour of consistent quality capable of making good finished products.