Miller Magazine Issue: 122 February 2020

46 COVER STORY MILLER / FEBRUARY 2020 high-quality wheat in a failed manufacture. Wheat quality characteristics change according to the user (farmer, mill- er, and end-user). The millers need to control on both raw materials and manufacture to produce a good flour baking quality and continuous uniformity. The wheat flour quality is determined by its suitability for a specific final product. Flour quality characteristics are af- fected not merely by wheat suitability for the specific final product, which can be determined by some wheat quality characteristics classified as direct factors, but by the type of processing equipment and the suitability of this kind of wheat for milling process all classified as indirect factors. The manager of a mill laboratory has to manage all of the wheat, milling streams, and produced flour characteristics. The quality department and lab facility should be as much as possible closed and nearby the mill, providing the service of sampling, inspections, analysis, and reporting, with reli- able quality plan and system. It is important to use appropriate standard methods and procedures in the flour quality testing laboratory. Common standard methods used in the food industry that are most applicable to a milling quality control laboratory are pub- lished by the American Association of Cereal Chemists In- ternational (AACCI) and the International Association for Cereal Science and Technology (ICC). The production of uniform bakery products requires con- trol over the raw materials used in their formation. Flour is a biological material and when obtained from different sources can vary considerably in its protein quality, protein quantity, ash, moisture, enzymatic activity, color, and phys- ical properties. The baker needs to be aware of any vari- ations in these characteristics from one flour shipment to the next. The purpose of flour testing is to measure specific characteristics of flour. Ideally, the results of these tests can be related to the flour’s performance in the bakery. MOISTURE The moisture content of the flour is important for two reasons. Firstly, the higher the moisture content, the lower the number of dry solids in the flour. Flour specifications usually limit the flour moisture to 14% or less. It is in the miller’s interest to hold the moisture as close to 14% as possible. Secondly, flour with greater than 14% moisture is not stable at room temperature. Organisms naturally pres- ent in the flour will start to grow at high moistures, produc- ing off-odors and flavors. ASH Ash is the mineral material in flour. The ash content of any given flour is affected primarily by the ash content of the wheat from which it was milled and it’s milling extraction. The goal of milling is to separate the endosperm from the non-endosperm parts of the wheat kernel. This separating is difficult and never clean. Thus, there is always contamina- tion of endosperm with non-endosperm and vice versa. As flour yield is increased, the amount of contamination with non-endosperm increases and the ash content increases. Thus, the ash content is a good and sensitive measure of the contamination of the endosperm. PROTEIN The flour protein content is an important parameter for bread flour. Flours containing higher protein content are more expensive than flours of lower protein content. Like- wise, flours with very low proteins for cakes are also more expensive. There is usually, but not always, a good correla- tion between protein content and bakery performance of flour. The quantity of protein is extremely important in the baking performance of flour. FREE FATTY ACIDS The level of free fatty acids in flour milled from sound wheat is very low. However, if either the wheat or the flour is subjected to poor storage conditions (high moisture and/ or high temperature), enzymes will degrade the native grain lipids and produce free fatty acids. Thus, the level of free fatty acids is a good measure of the storage conditions of either the grain or the flour. Flours with high levels of free fatty acids will be more subjected to rancidity than will sound flours. This is of little importance in bread but quite important in dry products (cookies, crackers, croutons, pret- zels, etc.). DAMAGED STARCH The starch in wheat occurs as partially crystalline gran- ules. When placed in excess water, the granules will absorb about 30% of their weight. The crystallinity of the granules restricts it from absorbing additional wa- ter. During milling, some of the granules are damaged. The damage results from the shear of the granule during roller milling. The shear shatters/ruptures some of the crystals. The damage may include the entire granule or just a part of it. This loss of crystals allows the granule to take up more water and swell more. Damaged starch will absorb as much as 300X its weight in water. Hard wheat flour contains a much higher level of damaged starch than does soft wheat. This is because the soft wheat crushes easily during milling and does not subject the starch to as much shear. Damaged starch is a positive factor in bread flour because it increases the water absorption. High water absorption in- creases the yield of dough and bread from flour, which has obvious positive effects on bakery profits. Damaged starch is a strong negative in flours for cookies and other dry fin- ished products. The damaged starch is highly susceptible to α - amylase attack. Much of the damaged starch is degraded to maltose and small dextrins by the combination of α - and β - amy- lase. This is the major reason that bread flours are malted ( α - amylase added) at the mill. If the damaged starch is not removed during fermentation it interacts with the glu- ten and reduces bread volume. Most hard wheat flours will