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Alpha-Amylase, Diastatic Activity of Flour, and Falling Number

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Alpha-amylase is a crucial enzyme found in flour that directly affects the quality of dough and baking. Its main function is to convert starch into sugars, which serve as a food source for yeast activity. Furthermore, these sugars contribute to the browning of the dough during the baking process as residual sugar in the dough.

Here is a brief explanation of how this process, also known as, diastatic activity (or enzymatic activity) occurs:

1. Flour is mainly composed of microscopic starch granules, each containing long starch molecules.
2. During the milling process, some starch granules become damaged, exposing them to the action of the alpha-amylase (α-amylase) enzymes.
3. Alpha-amylase enzymes break down the long starch molecules into medium-sized molecules, forming a carbohydrate called dextrin.
4. Subsequently, beta-amylase (β-amylase) enzymes target the dextrin molecules and convert them into a disaccharide called maltose.
5. Yeast then breaks down maltose into glucose, which it consumes during the fermentation process. Additionally, maltose and glucose accumulate in the dough as residual sugar.

As can be seen, the role of amylase enzymes in yeast’s food production is crucial. Within this process, alpha-amylase plays a vital role – without the activity of alpha-amylase, the beta-amylase enzymes will not be able to sufficiently breakdown starch on their own.

The glucose produced during this process accumulates as residual sugar in the dough. These sugars are responsible for the browning of the dough during baking through the Maillard reaction; Therefore, the alpha-amylase activity in the flour also affects the degree of browning during baking.

The main factor that affects alpha-amylase levels in wheat is its stage in the life cycle. “Young” wheat has low levels of alpha-amylase, while sprouted wheat has very high levels. Other factors that influence alpha-amylase levels include the type of wheat and its growing conditions.

In a typical scenario, when wheat reaches maturity, it enters a dormant state. However, if the wheat undergoes germination due to factors such as sub-optimal storage before milling or late harvesting, the level of alpha-amylase increases significantly (up to 5000 times compared to dormant wheat).

Using flour with high levels of alpha-amylase can result in excessive production of dextrins in the dough, exceeding the capacity of beta-amylase to break them down into maltose, making the dough sticky and difficult to handle, and the crumb of the baked good unchewable. In case this happens, there is no solution other than switching to a different flour.

To prevent wheat from entering a germination state, it is generally harvested when alpha-amylase levels are very low. As a result, it is often necessary to artificially add alpha-amylase to the flour during its production process.

Falling Number

The method used to measure the level of alpha-amylase in flour, also known as diastatic/enzymatic activity, is called Falling Number (FN). FN values are measured in seconds and are inversely related to the alpha-amylase concentration in the flour; In other words: a lower FN value indicates higher diastatic activity, and vice versa; Flours with high diastatic activity will have low FN values, while those with low diastatic activity will have high FN values.

FN values range from 60 (indicating very high diastatic activity) to 400 (indicating very low diastatic activity). Standard bread flours typically have a FN value of 220-260.

The table below presents a summary of FN values:

Falling NumberComments
150 and belowVery high enzymatic activity. A flour with such a high FN is milled from sprouted wheat. Using this flour will result in a sticky crumb with an underbaked texture. This flour is not suitable for baking unless it is mixed with another flour that has a higher FN value
150-220higher than normal enzymatic activity. The flour requires “correction” through mixing with other flour or the use of specific leavening and baking techniques
220-280Ideal enzymatic activity for most baking purposes
280 and aboveLow enzymatic activity. Ideal for baking at high temperatures (350°C/660°F and above)

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