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The Mixolab

quality control

There are many ways to measure the quality of flour. We can analyze its composition (protein, humidity, etc.), measure a specific component (gluten, starch, etc.) or even, and in order to more closely test the conditions of use, analyze the dough. For this last type of measurement there are generally two types of equipment:

  • Those that analyze the consistency of the dough during kneading
  • Those that analyze the characteristics of the dough after kneading

Mixolab belongs to the first category. The original idea appeared in Belgium in the 70s and 80s under the name of Pétrinex. Manufactured on demand by an astute engineer, it had the advantage of being able to analyze the behavior of the dough during the heating phase, and to detect the presence of germinated batches in this area, which is fairly sensitive to the phenomenon. The concept gradually died out before reappearing in the early 2000s, again in Belgium, under the name Multigraphe.

As an evolution of the Multigraphe, the Mixolab is first and foremost a recording mixer. In other words, it is capable of measuring the consistency of the dough at any time, thanks to a torque sensor (torque (in Nm) produced by the dough between two kneading elements during kneading (Figure 1)).

        

This type of measurement has been used for many years in devices such as the Farinograph®. Where the Mixolab stands out, is that it is the only device which can heat and cool the dough, thereby measuring the changes in consistency which results from changes in temperature, and thus allowing the user to anticipate the behavior of the dough in baking, in addition to the kneading behavior.

The operating principle of Mixolab is widely documented, but to recap, in its standardized protocol [1] it consists of 6 phases (Figure 1):

  1. Adaptation of the water absorption to achieve a constant consistency (C1): measurement of the water absorption capacity
  2. Kneading at constant temperature which makes it possible to measure conventional parameters such as development time and stability (CS).
  3. An increase in heating temperature which shows a weakening of consistency linked to changes in the gluten network. This phase leads to a consistency minimum (C2).
  4. An increase in consistency corresponding to the increase in viscosity resulting from the gelatinization of starch (C3)
  5. A stable phase at high temperature which allows the stability of the starch gel to be measured and reveal its enzymatic degradation by amylases (C4)
  6. Cooling, which makes it possible to start the starch reversion (retrogradation) phase and sees the consistency of the dough increasing to varying degrees according to the characteristics of the starch, followed by a stabilization of the temperature at 50° C. (C5).

For all the new applications which it brings, Mixolab sometimes disturbs the most conservative users. We often hear people questioning kneading at the same time as baking because "we don't knead the dough at the same time as we bake it". It's true, but in the industry you don't inflate dough balls (see "Alveograph"), and nobody makes bread by pulling on a ball of dough with a hook either.

To measure what is happening, you have to "move out of the box" and innovate. This is what Mixolab does. And in this respect, it is a great machine for developing new products. It is a known fact that when we make bread, pizza or noodles, we work the dough to a relatively high consistency. I emphasize the two terms "dough" and "high consistency".

Some devices measure the gluten characteristics, others the starch. Does knowing the characteristics of one or the other separately, and with tests far removed from the final use conditions, allow us to anticipate their joint action? Debatable.

Mixolab has the advantage of analyzing the dough, whether it is manufactured (mixed in the instrument) or taken directly from the production lines. And this, we repeat, is fundamental, because everything is about balances and interactions in the dough. Take the water for example.

When bakers hydrate their dough, they try to obtain a consistency that will allow them to work it in an optimal manner. Therefore, compared to its water absorption potential, the dough is a relatively under-hydrated medium. In other words, there isn’t enough water to go around. Damaged starch, which is very hygroscopic, has a tendency to capture free water more quickly than protein which, in fact, will be less hydrated. During kneading, there is a certain redistribution of water from the starch to the protein which allows each to develop the gluten network. The gluten properties will therefore depend on the availability of water, which is a far cry from tests that form gluten by hydrating it completely. Secondly, gelatinization of the starch. This step requires water, but, at the outset, part of the moisture is fixed to the protein. As a result, gelatinization of the starch will be much more limited than what would be observed in viscometers where the starch is "drowned" in water and can express itself without constraint.

The issue is not about questioning the tests mentioned, which are very useful for knowing the potential of gluten and starch in conditions that are ideal for their use. The issue is to note that observing what occurs in an environment close to real use conditions is inevitably of interest.

Of interest and certainly more complex because, as in reality, the result observed has not only one variable, but several. Research has allowed us to move forward in explaining these phenomena, and tools which simplify this research have also been developed.

If companies that manufacture enzymes or improvers are today large users of Mixolab, it is because they see it as an effective means of measuring the performance of their products. In the same way, the second transformation comes about from an interest, not only in the development of new products, but also in controlling the quality of the raw materials. We should also mention the manufacturers of gluten-free products, who can work on complex formulations on a small scale before moving on to the pilot phase.

The Mixolab is a good example of the constant need for innovation and the need to overcome established barriers and concepts in order to objectively look at what new instruments can bring to all levels of the cereal sector, from selection to bread-making.

 

[1] In addition to the internationally standardized protocols, the Mixolab allows a complete adaptation of the test conditions, which makes it a particularly suitable device for the analysis of new products.

Mixolab

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