“Flour quality control is a puzzle in which each piece corresponds to the information given by one testing method. To see the quality of the product, it is necessary to know how the results of the different tests are linked. Quality control should not be building specifications and filling in numbers: it should give the information required to improve quality and customer satisfaction. Considering all the QC results as a whole to understand and improve quality is the main challenge of the coming years and CHOPIN Technologies is dedicated to provide these solutions to the industry.”
Gregory VERICEL – Marketing Director, CHOPIN Technologies
Flour. It seems so simple. For most consumers, flour is just flour. A unique and uniform white powder. Before working in the flour industry, no one would doubt how complex flour is, how many elements compose flour, how variable it can be. Approximately 100 years after flour quality control history truly began with the invention of instruments such as the Alveograph, who would guess that everything is not known about flour?
Flour quality control is a puzzle in which each piece corresponds to the information given by one testing method.
A lot of methods are available on the market for controlling flour quality. CHOPIN Technologies is dedicated in developing new instruments and new methods, which bring to light new pieces of the puzzle.
A comprehensive Quality Control
A comprehensive quality control (QC) can be seen as a three step process. The first step is analyzing the composition of the sample: WHAT is in the flour (quantitative analyses). The second step consists of knowing HOW the different components behave together. It corresponds to the rheological analyses, knowing how flour behaves when combined with water and how the resulting dough behaves during mixing and processing. The third is to understand WHY dough behaves the way it does (functionality analyses).
Composition – WHAT
Uncontrolled sprouting makes flour unusable for human food as high amylase activity may lead to significant problems like sticky dough, bread with low volume and excessively red crust. Consequently, it is important for the industry to isolate sprout damaged loads of grain as early as possible.
Developed in the early 1960’s, the Hagberg falling number method provides a rapid means of determining the α-amylase activity in sprout damaged wheat or rye. This method is widely accepted, and standardized by international organizations (ICC, AACCI, ISO and ASBC).
The Amylab FN, developed by CHOPIN Technologies, measures α-amylase activity following the Hagberg falling number method or the new Testogram method. Instead of measuring the time required for the plunger to fall down the tube and go through the starch gel sample (between 60 and 500 seconds, average 325 seconds), the Testogram records the consistency during 90 seconds of constant shaking and determines if there is sprout damage in the sample. As a result, the Testogram method test gives an accurate prediction of the traditional FN value and provides an average of 66% more productivity to the user, compared to the falling number method. The Testogram protocol may also be adjusted to measure the impact of added fungal amylase, used to optimize flour enzyme activity.
In the mill, protein, moisture and ash are the most common parameters measured for the composition of flour. Near infrared systems are commonly used to measure them. Where most of the instruments of the market are capable of giving accurate results on moisture and protein, ash is a trickier parameter to tackle with infrared technology. Ash content is a common flour composition parameter, but also a key indicator of milling yield. If millers are able to get closer to the maximum value of ash required by end-user’s specifications, they will increase their milling yield, so they will increase the amount of sell-able flour. To meet this goal, measurement needs to be very accurate. The reference method (NF ISO 2171), using the ash furnace, has this accuracy, but requires 3 hours.
The Spectralab, new near infrared analyzer from CHOPIN Technologies, designed for process control in flour mills, provides this result in only 30 seconds, with an average error on ash measurement similar to the reference ash furnace method (only 0.017%). It is then possible to use ash measurement as a routine process optimization test.
Rheology – HOW
Composition only tells part of the story. Examples are found daily about wheat with similar protein content but very different end use quality. That is why it is absolutely necessary to add a second step: rheological testing.
Dough properties – gluten
One of the first rheological methods, invented in the 1920s, is the Alveograph test. It is used by wheat and wheat flour researchers around the world. It is the globally accepted standard for flour analytical evaluation. In the bread making process, gas is developed and exerts pressure on the dough piece in a multilinear process. The Alveograph is the only test that measures the characteristics of the dough in a multilinear manner rather than a straight linear manner.
The Alveograph measures how much pressure and how much time is necessary to create and burst an air bubble in the dough. Although many more measurements are possible, the four most common are:
– P (Tenacity) indicates the maximum pressure that was withstood before a bubble was formed. This is an excellent indicator of the strength of the flour.
– L (Extensibility) stands for the height of the bubble that was achieved, measured from where the slope of the bubble started to the top of the bubble. This shows how flexible the dough is.
– Ie (Elasticity) is the ability of a dough to return in its original state when the stress disappears.
– W (baking strength or energy) is the combination of all 3 previous parameters and represents the surface under the curve.
Dough properties – protein & starch
Flour dough is an extremely complex product primarily consisting of water and flour. The two major components of flour, protein and starch, react very differently in mixing and have different functions in baked goods. They play a major role in the development of the dough and eventually in the quality of final product. Released on the market in 2005, the Mixolab is the only device that measures both to provide a more complete rheological test by using both heating and cooling cycles. The Mixolab measures torque generated by the development of dough.
The Mixolab offers a variety of operating protocols. The standard “Chopin +” protocol is most widely used for the evaluation of wheat flour. This protocol enables the user to evaluate dough behavior during mixing, protein quality, starch gelatinization, amylase activity and starch retrogradation. No other device can provide such a complete picture. The Mixolab Simulator mode enables the user to develop curves that are fully comparable to those created by the Farinograph®.
The Mixolab 2 has an assortment of additional modes designed specifically for many non-wheat grains and pulses. If the standard curves do not meet specific applications, the user can change most settings to create custom protocols.
Functionality – WHY
Flours with similar compositions and rheological properties can exhibit different performances on a process line. It shows some information and understanding is missing. The third and last step of comprehensive QC brings answers to these.
Glutenins, damaged starch and pentosans are functional components affecting the behavior of dough during the production process and during baking. The glutenins affect the extensibility and elasticity of the dough, the damaged starch affects its stickiness, and the pentosans have a significant effect on the dough’s viscosity.
The Solvent Retention Capacity method is a measure of hydration based on the increased swelling capacity of the flour’s different polymers when brought into contact with certain solvents – distilled water, 5% lactic acid in distilled water (to measure the glutenins), 5% sodium carbonate in distilled water (to measure the damaged starch) and 50% sucrose in distilled water (to measure the pentosans).
Conventional rheology tools measure the combined effects of these three polymers. The SRC method is complementary to these tools (the Alveograph for example) for better understanding each polymer’s individual contribution to the final behavior of the dough. The water absorption potential of a flour is determined by the three functional polymers. In biscuit-making, the industrial producer seeks minimal water absorption from the damaged starch and pentosans. Effectively, the same global absorption rate can have different causes, which subsequently affect the behavior of the dough during the production process in different ways.
By analyzing the contribution of each polymer, SRC testing provides additional information, allowing the behavior of flours and doughs to be more fully understood. The manual SRC procedure is a standardized method: AACC (56-11).
The SRC-CHOPIN completely automates the different stages of the SRC method. By eliminating all the variations resulting from manual operations, the SRC-CHOPIN provides consistent results.
Conclusion and perspectives
Another challenge of flour quality control is to know how the different pieces of the puzzle come together. To see the big picture, it is essential to know how the different pieces are linked. To see the quality of the product, it is necessary to know how the results of the different tests are linked. Quality control should not be building specifications and filling in numbers: it should give the information required to improve quality and customer satisfaction. Considering all the QC results as a whole to understand and improve quality is the main challenge of the coming years and CHOPIN Technologies is dedicated to provide these solutions to the industry.
In our previous article titled "Ensuring Postharvest Grain Quality and Marketability with Advanced Software" information is given about "grain quality".