Although protein receives the most attention when it comes to describing flour quality, it is important to remember that flour is made up of nearly 70-80% starch.
Image Credit: KPM Analytics
There are two kinds of starch in flour: intact starch and damaged starch.
All milling, whether industrial or laboratory-performed, will unavoidably result in some damaged starch. While comparing the behavior of a damaged starch granule to that of a native granule, it is clear that:
- Its water absorption capacity has been multiplied by nearly 10
- It is much more susceptible to hydrolysis by amylase (an enzyme with the capacity to break down the glucose chains that make up starch).
Image Credit: KPM Analytics
This physical modification of the starch granule has a significant impact on the baking industry.
The initial effect is quite positive. It enhances the water absorption capacity of flour by several percentage points.
The economic impact may also be significant and can be viewed in two ways. Take the below flour with an absorption potential ranging from 64 to 67% as an example:*1
- Possibility 1: More bread can be made with the same amount of flour.
- ~1,000 kg of 64% flour at 1,640 kg of dough yields 6,560 loaves, weighing 250 g each*2
- ~1,000 kg of 68% flour at 1,680 kg of dough yields 6,720 loaves, weighing 250 g each
*1. These calculations only include flour and water. Yeast, salt, and other ingredients are not taken into account in this example.
*2. Mass of dough before baking.
That amounts to 160 more loaves for just the cost of the water.
- Possibility 2: Making a specific amount of bread with less flour.
- ~6,500 loaves made from 64% flour require 1,625 kg of dough at 991 kg of flour
- ~6,500 loaves made from 68% flour require 1,625 kg of dough at 964 kg of flour
That equates to a savings of 27 kg of flour.
It is obvious that the financial impact for companies that manufacture huge amounts of bread each hour is enormous.
The second impact may be more difficult. Although the damaged starch absorbs more water, it does not retain it as effectively. In reality, damaged starch is very hygroscopic and readily absorbs water (which explains its impact on absorption potential).
However, the granules generally release that water again during the mixing phase. Initially, the liberated water will be absorbed by the protein, a key component of the dough, to complete its hydration.
However, once the protein is fully hydrated, if water continues to seep from the damaged starch granules, it will separate from the dough and produce stickiness. A balance must be struck between protein levels and starch damage.
- Between the advantages of a larger hydration potential and manufacturers’ desire to prevent stickiness in their manufacturing lines, there is an ideal balance that can be reached.
The third effect occurs during fermentation. A broken starch granule is easier for amylase to break down. This leads to increased sugar production, which causes a number of phenomena:
- The activation of carbon dioxide gas production: This causes the dough to rise, which will increase the volume of the bread as long as the protein network is able to retain the gas. Excessive gas generation can also result in excessive pressure, rendering the dough porous and unstable. The effect is heightened in the oven, where heat causes the gas to expand. The structure is thus prone to collapse, resulting in low-volume loaves despite the fact that the dough rose well.
- When yeast is unable to use all of the sugar produced, the sugar remains in the dough and is more likely to contribute to caramelization or a Maillard reaction, perhaps resulting in excessive browning of the bread’s crust.
In the finished product, one final effect can be observed. If everything goes well during bread production, the water absorbed by the damaged starch will be released very slowly, enhancing the freshness and shelf life of the bread.
It is easy to see that for the baking industry, the key phrase for damaged starch is “not too much and not too little.” There is an optimum, depending on the type of product as well as the production process (Figure 1).
In any case, the most crucial thing to consider is the impact that damaged starch may have on final product quality and recognize the importance of measuring it.
Figure 1. Optimum starch damage for various grain products (relationship between protein levels and optimum starch damage). Image Credit: KPM Analytics
This information has been sourced, reviewed and adapted from materials provided by KPM Analytics.
For more information on this source, please visit KPM Analytics.