Making good bread require, of course, good bakers but also… good wheat! Indeed, you cannot use the same wheat to make flour for toast, sandwich bread, brioche, baguette… In order to decide of a suitable use for a wheat contracts, some tests are practised in agriculture field laboratories. Starch is the major component of flour as it represents at least two thirds of the weight of grain [1]. As nature does things well, a enzyme necessary for bread making industry is naturally present in wheat seeds: it is alpha-amylase. This enzyme is able to transform starch into simple sugar molecules, glucose and maltose. Focus on Alpha-amylase: from starch to maltose and glucose [2] Starch is a mix of two polysaccharides, amylose and amylopectin, at different rate depending on the plants. This molecules are special because there are composed by a same building-block: glucose. That is why there are called homopolymers.
Figure 1: Amylose and Amylopectin In both case, these oxygen bond can be broken by adding water molecules. One units gets an OH- from the water molecules and the other part gets an H+ to make the OH at carbon 1 and carbon 4. Alpha-amylase hydrolyses polysaccharides of starch using this process. The bond breaks can generate free glucose or pairs of glucose, that is to say maltose. A good rate of maltose for a good dough fermentation Maltose formation rate from starch determine dough fermentation depending on alpha-amylase activity. . Without enough maltose, fermentation is limited so breads are flat and moist test is not well developed. However, too much maltose leads to sticky and dough weak in consistency. [3] When does it happen? A persistent rainy whether before or during harvest can lead to the undesirable germination of mature wheat seeds. Indeed, alpha-amylase rapidly attack wet starch. [4] We call this the sprout damage, which would be disastrous for bread-making quality! Why? Because damaged starch is able to absorb more water and consequently it gives sticky dough. [5] So alpha-amylase levels mustn't be too high in order to limit starch degradation. Hagberg and the falling number method or how to determine alpha-amylase activity At the end of the 1950s, Sven Hagberg and his co-worker Harald Perten precisely developed a method, called the Falling Number method, to determine the rate and activity of amylase in wheat flour. Thus, it gives informations about a possible sprout damage. [4] As this test can be practised on grain silo intake, it allows to choose the best wheat contracts to sell for bread making. A specific apparatus is needed to practice the falling number test. Figure 2: Hagberg apparatus Distilled water is added to flour at ambient temperature. However, starch is not soluble to cold water. So after a vigorous shake insuring a homogeneous mix, this test tube is placed in a boiling water bath. The operator stir the sample during 60 seconds. Starch begins to gelatinize under the increase of temperature so the slurry becomes more viscous. But the high temperature also promotes starch breakdown into glucose and maltose by alpha-amylase contained in the flour. As a consequence, we observe a decrease of the slurry viscosity. Recording slurry consistency levels allows to know alpha amylase activity. The viscosity is measured as the time (in seconds) necessary for the stem to fall into the test tube. Thus, the higher the activity of the alpha-amylase, the lower the viscosity will be and the lower the falling number will be. So how to know if a wheat contract is a good one for bread making? [5]
Any solutions?
It is easy to improve high falling number wheat contract by adding malt (germinated barley seeds) but for small falling number, the only solution is to mix wheat with a wheat of better quality. [6] References [1] Analyse Des Farines. 1st ed. La m eunerie Milanaise. Web. 15 Sept. 2016. [2] "Alpha Amylase". Science.marshall.edu. N.p., 2016. Web. 15 Sept. 2016. [3] "Hydrolases #Boulangerie.Net". Boulangerie.Net. N.p., 2016. Web. 15 Sept. 2016. [4] "Falling Number". Wikipedia. N.p., 2016. Web. 15 Sept. 2016. [5] [email protected], LEMON. "Analyse Du Temps De Chute Hagberg". Ssl10.ovh.net. N.p., 2016. Web. 15 Sept. 2016. [6] Lachance, Pierre. L’Indice De Chute (Hagberg). 1st ed. 2004. Print.
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