Miller Magazine Issue: 122 February 2020

48 COVER STORY MILLER / FEBRUARY 2020 have from 6-9% damaged starch by the AACC procedure. COLOR Flour color is important because it affects the crumb color of the finished product. The color of the flour used for vari- ety bread, that has a dark color because of non-wheat com- ponents in the formula, is not important. Unbleached flours have a creamy color because of the presence of carotenoid pigments in the endosperm. The level of these pigments and therefore the color of the flour will vary from flour to another. The level of pigments is under genetic control. The pigments can be readily bleached with benzoyl peroxide (mixed with the dry flour at the mill) or by enzyme active soy flour in the bread formula. Flour color can be judged by visual comparison with stan- dard patent flour. In the Pekar (slick test), the sample flour is slicked alongside the standard sample and their colors com- pared visually. This procedure is also useful to determine if the sample is contaminated with bran. Any color differences between the samples can then be readily evaluated. ENZYME ACTIVITY Although flour contains a large number of enzymes, only a few are measured and/or controlled. The most important enzymes in bread flour are the amylases. Beta-amylase is found in sufficient quantities in all flours. It has no action on native starch granules but does attack gelatinized and damaged starch. It acts from the non-reducing end of the gelatinized starch chain to produce maltose. It cannot go past a branch point so its action is stopped with a large part of the molecule still intact. This is called the beta limit dextrin. It will convert about 30% of the amylase and 45% of the amylopectin to maltose. The other amylase of importance in wheat flour is α -am- ylase. Flour milled from sound wheat contains little or no α -amylase. Bread produced from flours with low levels of α -amylase will be low in volume and have a rough-textured crumb. Thus, it is common to add malted barley or malted wheat flour to increase the α -amylase activity. Some millers will add fungal amylase preparations to increase the α -am- ylase activity. This requires a modified method of analysis. Although sound grain contains low levels of α -amylase, the level of activity increases rapidly if the grain is sprouted. This greatly increases the level of α -amylase and other en- zymes. α -Amylase Activity α -Amylase breaks the α -1 – 4 bonds in starch in a more or less random attack. It is not truly random as it does not break those bonds near a α -1 – 6 branch point. Because of its attack pattern, each break dramatically reduces the size of the resulting dextrin. As a result, the viscosity of the starch-water paste decreases rapidly. This is why α -amylase is sometimes referred to as the liquefying enzyme. Because of the rapid decrease in viscosity with each bond broken, the measurement of viscosity is a sensitive measure of en- zyme activity. The following three methods to measure α -amylase ac- tivity are all viscosity measuring procedures. 1) Falling Number The falling number apparatus consists of a boiling water bath, matched test tubes (to conduct heat at the same rate), a stirrer, a stirring apparatus, and a timing mechanism. Flour plus a known amount of excess water is placed in a test tube and shaken to disperse the flour. The tube is placed in the apparatus that stirs the sample as if it is heated. At the end of stirring, the stirrer is dropped from the top posi- tion. The number of seconds required for the stirrer to fall through the flour-water paste is the falling number. Sound flour will have a falling number of 400 seconds or