“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 providing these solutions to the industry.”
For the majority of consumers, flour is just flour, a uniform, and unique white powder. No one would doubt how many elements compose flour, how complex flour is, or how variable it can be prior to working in the flour industry.
Who would guess that everything is not known about flour, even around 100 years after flour quality control history truly began with the invention of instruments like the Alveograph?
Flour quality control is a puzzle where each piece corresponds to the information given by one testing technique. There are a number of techniques available on the market for controlling flour quality. CHOPIN Technologies is dedicated in developing new techniques and instruments that bring new pieces of the puzzle to light.
A Comprehensive Quality Control
A comprehensive quality control (QC) can be demonstrated in a three-step process. Analyzing the composition of the sample is the first step: WHAT is in the flour (quantitative analyses).
The second part is knowing HOW the different components behave together. It corresponds to knowing how flour behaves when combined with water, the rheological analyses, and how the resulting dough behaves during processing and mixing. The last is to understand WHY dough behaves the way it does (functionality analyses).
Composition – WHAT
As high amylase activity can result in significant problems such as bread with low volume, sticky dough, and excessively red crust, uncontrolled sprouting makes flour unusable for human food. So, it is crucial for the industry to isolate sprout damaged loads of grain as early as possible.
The Hagberg falling number method, developed in the early 1960s, supplies a fast way of establishing the α-amylase activity in sprout damaged rye or wheat. This technique is standardized by international organizations (ICC, AACCI, ISO, and ASBC), and is widely accepted.
Developed by CHOPIN Technologies, the Amylab FN measures α-amylase activity following the Hagberg falling number technique or the new Testogram technique.
The Testogram records the consistency during 90 seconds of constant shaking and determines if there is sprout damage in the sample, instead of calculating the time needed 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 technique provides an accurate prediction of the traditional FN value and gives an average of 66% more productivity to the user as a result of this, compared to the falling number technique. The Testogram protocol may also be altered to measure the effect of added fungal amylase, employed to optimize flour enzyme activity.
The most common parameters measured for the composition of flour in the mill are moisture, protein, and ash. Typically, near-infrared systems are utilized to measure them.
Ash is a more challenging parameter to tackle with NIR (near infrared) technology, where most of the instruments on the market are capable of giving accurate results on protein and moisture.
Ash content is a key indicator of milling yield, but also a common flour composition parameter. Millers will increase their milling yield if they can get closer to the maximum value of ash needed by end-users specifications, so they will increase the amount of sellable flour.
Measurement must be extremely accurate in order to meet this goal. The reference technique (NF ISO 2171) has this accuracy, using the ash furnace, but takes three hours. A new near-infrared analyzer from CHOPIN Technologies, the Spectralab, is designed for process control in flour mills and supplies this result in just 30 seconds.
It has an average error on ash measurement of only 0.017%, which is similar to the reference ash furnace technique. It is then possible to utilize the ash measurement as a routine process yield optimization test.
Rheology – HOW
Composition only tells part of the story, examples are found every day regarding wheat with very different end-use quality but similar protein content. That is why it is crucial to add a second step: rheological testing.
Dough Properties- Gluten
The Alveograph test, invented in the 1920s, is one of the first rheological techniques. It is employed by wheat and wheat flour researchers worldwide and is the globally accepted standard for flour analytical evaluation.
Gas develops in the bread-making process and exerts pressure on the dough piece in a multilinear process. The Alveograph is the only test which measures the characteristics of the dough in a multilinear manner instead of a straight linear manner.
Figure 1. The Alveolab.
The Alveograph measures the amount of time and pressure needed to create and burst an air bubble in the dough. Although many more measurements are possible, the four most common are:
- Ie (Elasticity) is the ability of dough to return in its original state when the stress disappears.
- L (Extensibility) shows how flexible the dough is and 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.
- P (Tenacity) is an excellent indicator of the strength of the flour, it is the maximum pressure that was withstood before a bubble was formed.
- W (baking strength or energy) represents the surface under the curve and is the combination of all 3 previous parameters.
Dough Properties – Protein and Starch
Flour dough is an incredibly complex product primarily made up of flour and water. 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 the final product.
Figure 2. The Mixolab 2.
Released 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 the dough.
There are a number of operating protocols offered by the Mixolab 2. For the evaluation of wheat flour, the standard “Chopin +” protocol is most widely employed. This protocol allows the user to assess dough behavior during mixing, starch gelatinization, protein quality, starch retrogradation, and amylase activity. No other device can give a complete picture like this.
The Mixolab Simulator mode allows the user to develop curves which are fully comparable to those created by the Farinograph®. The Mixolab 2 has a variety of additional modes which are designed for many non-wheat grains and pulses specifically.
Figure 3. The integrated MIXOLAB 2 software measures each of the standard curve parameters and converts them into six qualitative indexes.
The user can change most settings to create custom protocols if the standard curves do not meet specific applications.
Functionality – WHY
On a process line, flours with similar rheological properties and compositions can give different performances, which shows that some information and understanding is missing. The last step of comprehensive QC brings answers to these.
Damaged starch, glutenins, and pentosans are functional components that influence the behavior of dough during the production process and during baking. The damaged starch affects the stickiness of the dough, the glutenins influence the extensibility and elasticity, and the pentosans have a significant effect on the viscosity of the dough.
The Solvent Retention Capacity technique is a measure of hydration based on the increased swelling capacity of the flour’s different polymers when brought into contact with certain solvents – 50% sucrose in distilled water (to measure the pentosans), 5% sodium carbonate in distilled water (to measure the damaged starch), distilled water, and 5% lactic acid in distilled water (to measure the glutenins).
Conventional rheology tools measure the effects of these three polymers combined. The SRC technique 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 three functional polymers are used to establish the water absorption potential of a flour. The industrial producer seeks minimal water absorption from the damaged starch and pentosans when biscuit-making.
So, the same global absorption rate can have different causes, which subsequently influence the behavior of the dough during the production process in different ways.
SRC testing provides additional information by analyzing the contribution of each polymer, enabling 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 automates the different stages of the SRC technique completely. It provides consistent results by eliminating all the variations resulting from manual operations.
Figure 4. SRC-CHOPIN.
Conclusion and Perspectives
Knowing how the different pieces of the puzzle come together is another challenge of flour quality control. It is vital to know how the different pieces are linked in order to see the big picture.
It is crucial to know how the results of the different tests are linked in order to see the quality of the product. Quality control should give the information required to improve quality and customer satisfaction, it should not be building specifications and filling in numbers.
The main challenge of the coming years is considering all of the QC results as a whole to understand and improve quality, and CHOPIN Technologies is dedicated to providing these solutions to the industry.
This information has been sourced, reviewed and adapted from materials provided by CHOPIN Technologies.
For more information on this source, please visit CHOPIN Technologies.