Monday, September 21, 2009

Flour : Enzymatic Activity

As indicated in the last post, Didier Rosada talked at length about flour during last month's Artisan III workshop, detailing the testing process by which the miller determines the ash content, the protein content and the enzymatic activity. An enzyme is a big protein molecule which can catalyze a biochemical reaction when activated with water. Since enzymes are needed to transform complex sugars into simple ones which the yeast cells can process, the baker needs to know if a given flour contains enough enzymes to make bread. Enzymes are naturally present in the flour; they can also be added at the mill to give the baker better control of the fermentation activity. When wheat arrives at the end of its maturation, it starts getting ready for the new cycle of life (sprouting process) and within the kernel, enzymes - generally activated by heavy rains - start degrading complex molecules of starch as food for the germ. That's why farmers are so stressed out when rain is forecast and the combine they have booked for the harvest has yet to arrive: they risk losing one whole year of work. The miller tests the wheat when it arrives at the mill using the falling number method which "...measures the time taken for a plunger to fall to the bottom of a precision bore glass tube filled with a heated paste of wheat meal and water... The time taken (in seconds) for the plunger to fall is known as the falling number, and is 62 seconds for badly sprouted wheat." (Carl L. German, Understanding the Falling Number Wheat Quality Test). A falling number between 250 and 300 seconds indicates a flour with well-balanced enzyme activity. Most of the time, the falling number is equal or superior to 400, denoting low enzyme activity. If a miller receives wheat with a low falling number (indicating high enzyme activity), he knows that the sprouting process is well underway and that the quality of the flour will be poor for baking purposes. It might even be impossible to make bread with it. Sometimes bread can still be made but the dough may be very sticky, lack strength and rise poorly, fermentation may be too fast and/or crust color may be off. He then rejects that wheat or buys it at a much lower price for a different purpose (animal food for example). The miller boosts the baking properties of the flour by adding enzymes to it, most often malt. It is thus very important for the home baker to read the flour label. If it says "malted barley flour", you know the miller has added what is needed to make bread. If no indication is given, the only way to find out is to actually make bread. If fermentation is very slow and the crust remains pale, you need to add diastatic malt (.5% to 1%) to your next batch. Some millers also use fungal amylase (measured by a different test) to boost enzymatic activity. Fungal amylase isn't available to home bakers as it needs to be used in such minute quantities that it would be impossible for them to weigh it.

2 comments:

  1. Wow! Interesting stuff - just when I think I may be understanding flour and bread making, I realize I don't! Thanks for sharing.

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  2. Thanks for visiting, John! Half of the fun of bread baking is that we learn something new everyday (the other half is eating the bread!).

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