Baking strength is measured using the Alveograph and is a key parameter for dough analysis; it’s the famous "W” of the Alveograph test result chart. Over the years, the "W" has established itself as one of the most widely used measurements internationally, mainly for establishing customer / supplier specifications, but also for the registration of new varieties of wheat.
But what is the "Baking Strength"?
Technically, the “W” is calculated from the area under the Alveogram curve.
More than a force, it represents the work necessary for the deformation of the dough. This is why its symbol is "W" for "Work".
The term “baking” of “baking strength” is also reductive. While the Alveograph was originally used primarily for flour for breadmaking, this is no longer the case. Alveograph measurements are nowadays suitable for the analysis of many products, such as cookies, cakes, pizzas, pasta, sandwich breads, etc. The measured "strength" goes well beyond the initial bread baking definition. Therefore, it is more accurate to define “W” as the work of deformation required to swell a dough bubble until it breaks, regardless of the end use of the flour.
The "W" is important, but it shouldn’t be used alone!
It is considered an error to communicate only the W value. Stating, "I have a flour that makes 250 W," does not tell you anything about the quality of the flour. Keep in mind that the "W" comes from a surface, but it is quite possible to have the same surface (therefore the same W) with a flour having a high tenacity (P) and a low extensibility (L) and another which will have low tenacity and high extensibility (Figure 1).
A specification based solely on W does not in any way guarantee raw material consistency, since the same W can correspond to very different flours. To avoid this, always accompany the "W" with another characteristic value of the curve. We recommend the “P”, the “L” or even the “Ie” (elasticity). Although "P / L" is often used in addition to "W", its use is not recommended here for a very simple reason. As its name suggests, the “P / L” depends on both the “P” and the “L”. It is sensitive to natural variation (uncertainty) on the measurement of the “P” AND with the uncertainty on the measurement of “L”. The result is that the “P / L” measurement by nature is more subject to variation (more uncertain) than the others.
What is a good "W" value?
This is a frequently asked question that cannot be answered. First, because, as we have seen, the "W" is subjective and can correspond to very different curve configurations. Second, because each industry needs corresponding “W” levels. The biscuit maker will prefer rather low “W” values, accompanied by low “P” and high “L” (low tenacity, high extensibility), while brioche manufacturers want high “W” resulting from high tenacity (P) associated with high extensibility (L) and elasticities (Ie).
This notion of "Force" is relative, and it is interesting to note (Figure 2) that if there is a good relationship between the “W” measured at constant hydration (HC) and adapted (HA), the WHA are always lower than the “W” measured at constant hydration (HC) and adapted (HA). WHC (in particular because of the fall of the "P" which strongly impacts the surface). This observation largely explains the resistance of certain manufacturers to use the HA protocol, which is seen as penalizing for the “W” whereas it is only a change of reference system, potentially more relevant for certain users because, in theory, closer to the real conditions of use of flour.
During this study, 150 wheats from all over the world were ground using LabMill to obtain laboratory flours. These flours were analyzed with the Alveograph according to the standard constant hydration protocol, and according to the adapted hydration protocol. The only difference between the test conditions is the level of hydration, which has been matched to the actual water absorption capacity of the flour.
As indicated previously, we observe a strong relation between W and W_HA. However, there is a slope: W_HAs are always weaker than W_HCs, and this is even more obvious when W_HC is high. This is because generally the higher the W_HC, the higher the water absorption capacity. If a lot of water is added, the "P" decreases a lot, which strongly impacts the “W”.
For example, a flour that shows a W_HC of 200 may have a W_HA of 180. A flour showing a W_HC of 400 will be much weaker at adequate hydration (<300). This obviously does not change the quality of the flour: it is the same flour analyzed under different conditions.