Milling Procedures (shared using http://VisualBee.com).
Baking and Confectionery Technology
Wheat Flour MillingWheat Flour? Wheat flour is a powder made from the grinding of wheatused for human consumption.Wheat flour is the most common flour used in baking.There are different types of wheat flour, and theyredistinguished by the amount of gluten they contain. Wheat is unique or its protein content (gluten).
What is Gluten? Gluten is protein composite( gliadin and a glutelin) foundin foods processed from wheat and related grain species,including barley and rye. It gives elasticity to dough, helping it to rise and to keepits shape, and often gives the final product chewy texture. It gives baked goods their structure. When dough iskneaded, these glutens develop and become firm.
• Whole grain flour contains all grain parts• Refined, enriched flours are made from the endosperm only• Endosperm (83% of kernel) Energy for plant growth Carbohydrates; protein for people• Bran layers (14.5% of kernel) Protects seed Fiber, B-vitamins; minerals• Germ (2.5% of kernel) Nourishes seed Antioxidants, Vitamin E, B-vitamins
THE MODERN FLOUR MILLING PROCESSThe basic aim of the milling process -to break the wheat grain, remove the outer bran layers and the germ . -to grind the pure endosperm into flour.This is achieved by a gradual series of operations including -a breaking stage, -a reduction stage and -a series of separations of the ground material by means of both particle size and density.
Wheat Flour MillingFirst wheat is cleaned and conditioned to a suitable moisturelevel for milling before passing through the BREAK ROLLS.The break rolls consist of pairs of fluted rolls running in oppositedirections at a differential speed so that both a shearing andgrinding action is produced.The stock from the first roll is sieved in a plansifter and brannymaterial with endosperm adhering is separated and sent to the nextset of break rolls.
Wheat Flour MillingCoarse endosperm chunks (SEMOLINA) and finer endospermparticles (MIDDLINGS) are separated in the purifier and sent to thereduction rolls.Any remaining fine bran particles may be removed by the purifierusing a combination or sieves and air currents.Generally, four break stages are used with successively finer flutingsand gap settings for each stage.After the final break stage, bran is removed as commercial mill bran.The coarse endosperm particles are ground to flour using smoothREDUCTION ROLLS.After each grinding, flour is removed by sieving in a plansifter andovertailings of the sieves are sent to subsequent reduction rolls.
Flour MillingThe number of reduction stages depends on the flour yieldrequired but in recent years, the number of stages has graduallybeen reduced by the use of impact equipment (flake disruptors,entoleters).After the final reduction roll, any remaining fine bran, endospermand germ is removed as POLLARD.Germ is normally flattened on the reduction rolls and, in certainmills, separated by sieving.The amount separated is generally less than 2%.Bran and pollard are sold as animal feeds, although bran andgerm are also packaged separately for human consumption.
EXTRACTION RATEThe number of parts by weight of flour that is produced from one hundredparts of wheat is termed the FLOUR YIELD or EXTRACTION RATE.This figure is used as an index of the overall efficiency of a flour millingsystem.In practice, the limit of white flour extraction has been 75-79%;Further they increases in the extraction rate lead to darker flour colour andhigher ash and fibre contents which adversely affect the breads baked from them.Milling to produce white flour results in the removal of varying amounts ofbran, pollard and germ which together constitute 12-15% of the grain by weight.The national average extraction rate has been reported as 75.8% with a rangeof 69-80% depending on the efficiency of the mill.
DISTRIBUTION OF NUTRIENTS DURING MILLING Wheat flour is an excellent source of complex carbohydrates. Other than gluten flour, all types of wheat flour derive at least 80percent of their calories from carbohydrates. Depending on the flour type, the percent of calories from proteinranges from 9 to 15 percent, except from gluten, which has 45percent protein content.Flour, comprising about 75-78% of the total mill products, generallycontains 90-95% of the grains protein, 50% of the thiamin (vitaminB1), and 30-60% of the minerals.Bran and pollard contain most of the grains fiber and a variableamount of the vitamins and minerals.
Types of wheat Flour1. Hard wheat flour: including hard white, hard red winter, and hard red spring wheat have a high protein content (ranging from 10 to 14 percent), which means the gluten forming capacity is also higher, suitable for baking yeast breads and similar products.2. Soft wheat flour: include soft white and soft red winter, which are both used for products, such as cakes, cookies. The protein content of soft wheat varieties, such as cake and pastry flour, usually ranges from 6 to 10 percent.3. Durum wheat flour : is the hardest wheat grown. It is used almost exclusively for making pasta and is most often ground into a granular flour with a light yellow color known as semolina,
Classifications of wheat flour based on gluten content and purposes of uses1. All-Purpose Flour: All-purpose flour is formulated to have a medium gluten content of around 12 percent or so.2. Bread flour is a strong flour, meaning that it has a relatively high gluten content — usually around 13 to 14 percent.3. Cake flour is made from soft wheat and has a lower gluten content — around 7 to 9 percent. Its grains are visibly finer than bread flour, and it is much whiter in color. Its fine, soft texture makes it preferable for tender cakes and pastries
4. Pastry flour is slightly stronger than cake flour, ataround 9 to 10 percent gluten. It can be used for biscuits,muffins, cookies, pie doughs and softer yeast doughs. Ithas a slightly more off-white color than cake flour.
NON-WHEAT FLOURS Types of Flour Ground from CornSeveral varieties of corn are used to produce different typesof corn flour. The degree in which the corn is milled andprocessed also determines the type of flour that is produced. Corn FlourA type of flour milled from dried kernels of yellow corn. Cornflour is very useful for gluten-free quick breads.Because corn flour contains no gluten, it must be blendedwith wheat flour when preparing yeasted breads.
Types of Flour Ground from Rice Rice flour is produced from uncooked rice that has beenground into a powder ranging from course to very fine. Riceground to a course texture is often used in baked items suchas cookies and cakes. Standard rice flour is available in brown or white varieties.Brown Rice Flour Brown rice flour is a type of flour made from rice kernelsthat have been processed to remove the outer hulls, but notthe nutritious bran layers covering the kernel. When the kernels are ground into flour, the resulting color isonly a shade darker than flour milled from polished rice andthe texture is not quite as smooth.
White Rice FlourWhite rice flour is a type of flour produced fromgrinding polished rice (the bran and germ have beenremoved) into a powder.White rice flour can be used as a thickening agent forsauces and puddings.It is also very popular for the preparation of a variety ofAsian noodles.It is used in some baked goods, such as cakes,cookies
Types of Flour Ground from Rye Rye flour is produced from grinding the grains of rye into apowder. Like most other types of flour produced from grains, ryeflour may be ground into varying degrees of fineness rangingfrom course to very fine. It also is available in light, medium, and dark varietiesaccording to the quantity of bran included in the flour. The type of protein necessary for gluten formation is lowerin rye than wheat, but it is higher than in most other grains. Rye flour is often combined with wheat flour when bakingrisen breads.
Light Rye FlourDuring the milling process, the bran is removed from the ryeto produce light rye flour, which is a lightly colored and verystarchy version of rye flour. It is often used for making crustyblack breads.Medium Rye FlourMedium rye flour contains some bran, but not as much asdarker versions of rye flour. It is widely used in a variety of ryebreads and other baked goods.Dark Rye FlourDark rye flour is produced from the whole grain minus thehusk. The bran and the germ are retained, which are full ofnutrients.
Types of Non-Wheat Flour Ground from Other GrainsBarley FlourBarley flour is usually produced from barley, whichrefers to barley that has been scoured and polished toremove the husk and the bran.After the malting process has removed the sugar andstarch, the remaining barley (known as malted barleyflour), is steam dried, milled, and sifted to provide thefinished flour product.
Oat FlourOat flour is produced from hulled and cleaned oats. It isalso ground from rolled oats or oatmeal. Oat flour addstexture and a rich nutlike flavor to breads and otherbaked goodsSeven-Grain Flour or composite flour:Seven-grain flour is a commercially blended flourmixture of seven ground grains consisting of wheat, rye,corn, oats, barley, millet, and flax (or triticale). Usuallyused for the manufacturing of baked products.
Sorghum FlourSorghum, which has a sweet, nutty flavor, is often milledinto flour, but it lacks gluten, so it isnt suitable for makingyeast breads.Some other non wheat flours are:buckwheat flour , casava flour, potato flour, chapatiflour , chickpea flour