词条 | Wheat flour |
释义 |
| name=Wheat flour, whole-grain | kJ=1418 | protein=13.70 g | fat=1.87 g | carbs=72.57 g | fiber=12.2 g | sugars=0.41 g | glucose= | fructose= | iron_mg=3.88 | calcium_mg=34 | magnesium_mg=138 | phosphorus_mg=346 | potassium_mg=405 | zinc_mg=2.93 | sodium_mg=5 | manganese_mg=3.8 | vitC_mg= | pantothenic_mg=1.008 | vitB6_mg=0.341 | folate_ug=44 | thiamin_mg=0.447 | riboflavin_mg=0.215 | niacin_mg=6.365 | opt1n=Phosphorus 346 mg | opt1v= | opt2n=Copper 0.38 mg | opt2v= | opt3n=Selenium 0.071 mg | opt3v= | right=1 | source_usda=1 }} Wheat flour is a powder made from the grinding of wheat used for human consumption. Wheat varieties are called "soft" or "weak" if gluten content is low, and are called "hard" or "strong" if they have high gluten content. Hard flour, or bread flour, is high in gluten, with 12% to 14% gluten content, and its dough has elastic toughness that holds its shape well once baked. Soft flour is comparatively low in gluten and thus results in a loaf with a finer, crumbly texture.[1] Soft flour is usually divided into cake flour, which is the lowest in gluten, and pastry flour, which has slightly more gluten than cake flour. In terms of the parts of the grain (the grass fruit) used in flour—the endosperm or protein/starchy part, the germ or protein/fat/vitamin-rich part, and the bran or fiber part—there are three general types of flour. White flour is made from the endosperm only. Brown flour includes some of the grain's germ and bran, while whole grain or wholemeal flour is made from the entire grain, including the bran, endosperm, and germ. Germ flour is made from the endosperm and germ, excluding the bran. MillingTo produce refined (white) wheat flour,[2] grain is usually tempered, i.e. moisture added to the grain, before milling, to optimize milling efficiency. This softens the starchy "endosperm" portion of the wheat kernel, which will be separated out in the milling process to produce what is known to consumers as white flour. The addition of moisture also stiffens the bran and ultimately reduces the energy input required to shatter the kernel, while at the same time avoiding the shattering of bran and germ particles to be separated out in this milling process by sieving or sifting. The endosperm portion of the kernel makes up about 80% of the volume and is desirable because the products made from this white flour are often considered to have milder flavor, smoother texture, and, in the case of bread, greater volume. The balance of the kernel is composed of the bran and the germ which tend to be coarser. With the invention of the roller milling system in the late 19th century, the bran and the germ were able to be removed, dramatically improving the appeal of baked products to the public. The moistened grain is first passed through the series of break rollers, then sieved to separate out the fine particles that make up white flour. The balance are intermediate particles of endosperm (otherwise known as product middling or farina) and coarse particles of bran and germ. The middling then makes multiple passes through the reduction rolls, and is again sieved after each pass to maximize extraction of white flour from the endosperm, while removing coarser bran and germ particles. To produce whole wheat flour, 100% of the bran and germ must be reintroduced to the white flour that the roller milling system was originally designed to separate it from. Therefore, these elements are first ground on another mill (usually a pin mill). These finer bran and germ fractions are then reintroduced to the endosperm (white flour) to produce whole wheat flour made of 100% of the kernel of wheat. TypesWheat flour is available in many varieties; the categorization is regional, and the same name may have several different regional meanings. Canada
Fiji
Indian wheat floursIndian flours are generally categorized by how much of the grain is stripped away.
Southeast Asia
United StatesAmerican flours are categorized by gluten/protein content, processing, and use.
Other
Flour strength – W indexA device called Alveograph Chopin invented in 1921 by Marcel Chopin, provides an index called W that is now commonly used by professional bakers. W index measures the flour strength. The maximum of the curve, identified by P, represents the toughness of gluten, while L represents the extensibility, the higher the value of L the more elastic the dough will be. Flours between 90 and 160 W are called "weak flours". They have a low protein content, usually 9%, used to produce biscuits or cakes. Flours between 160 and 250 W have a medium force. They are used, for example, for Pugliese bread, pizza and focaccia. Flours > 300 W Flours with a high W are called "strong flours" because they have a great resistance to the deformation of gluten. In general, the longer rising time a bread product requires, the more a flour will need a high W, because it better retains the carbon dioxide produced in the fermentation.[7] National Flour in the United KingdomDuring World War II, the British government promoted "National Flour"; it was adopted in 1942 as a healthy and economic alternative to importing wheat.[8] The flour is described as being of 85% extraction, i.e. containing more of the whole wheat grain than refined flour, generally described as 70% extraction at the time. Parliamentary questions on the exact constitution of National Flour in 1943 reveal that it was "milled from a grist consisting of 90 per cent. wheat and 10 per cent. diluent grains. Authorised additions are calcium at the rate of {{convert|7|oz|g|abbr=on}} per {{convert|280|lb|kg|abbr=on}} of flour and dried milk at the rate of {{convert|2|lb|g|-1|abbr=on}} per {{convert|280|lb|kg|abbr=on}} of flour and customary improvers in normal proportions." The diluent grains were barley, oats and rye and customary improvers were "certain oxidising agents which improve the quality of the bread baked from the flour, and their nature depends on the kind of grain used, whether hard or soft.".[9] A survey of the composition of National Flour was conducted for the period 1946–1950.[10] National Flour was discontinued in 1956 against the recommendations of the MRC[8] as the government considered that the addition of nutritional supplements to refined flour removed the necessity for using National Flour on health grounds. Flour productionKenyaNational Flour was also a term for a flour introduced in Kenya by the colonial government which contained 70% wheat flour and 30% maize flour.[11] See also
References1. ^1 2 3 4 {{cite web | last = Chu | first = Michael | title = Wheat Flour | publisher = Cooking for Engineers | date = 2004-10-20 | url = http://www.cookingforengineers.com/article/63/Wheat-Flour | accessdate = 2009-08-14 }} {{Wheat}}{{Authority control}}{{DEFAULTSORT:Wheat Flour}}2. ^{{cite book|last=Bass|first=E.J.|title=Wheat Chemistry and Technology Vol. II Chapter 1: Wheat flour milling|year=1988|publisher=American Association of Cereal Chemists|isbn=978-0-913250-73-0|pages=1–69|editor=Y. Pomeranz}} 3. ^{{Cite web | url=http://wholegrainscouncil.org/whole-grains-101/definition-of-whole-grains | title=What's a Whole Grain? A Refined Grain? | the Whole Grains Council}} 4. ^{{cite web |title = Kate Flour |publisher = A Merrier World |year = 2008 |url = http://amerrierworld.com/kate-flour/ |accessdate = 2011-09-12 }} 5. ^{{cite web | title = Frequently Asked Questions - Is flour still bleached? | publisher = Flour Advisory Board | date = | url = http://www.fabflour.co.uk/faq/3/31/is-flour-still-bleached.html | accessdate = 2011-09-12 }} 6. ^{{Cite web|url=http://www.inchem.org/documents/iarc/vol73/73-17.html|title= IARC--Summaries & Evaluations: Potassium Bromate (Group 2B)|year=1999|website=International Agency for Research on Cancer}} 7. ^{{cite web|title=more information on "Flours for Pizza and Focaccia, the flour strength|url=http://www.smartitalianrecipes.com/italian-ingredients/flours-for-pizza-and-focaccia-flour-strength/}} 8. ^1 {{cite journal |doi=10.1136/bmj.1.4979.1347 |title=End of National Flour |journal= BMJ|volume=1 |issue=4979 |pages=1347–1348 |year=1956 }} 9. ^HANSARD 1803–2005,27 October 1943, Commons Sitting → FOOD SUPPLIES. Available online at http://hansard.millbanksystems.com/commons/1943/oct/27/national-flour 10. ^{{cite journal |doi=10.1002/jsfa.2740020502 |title=National flour survey 1946–1950 |journal=Journal of the Science of Food and Agriculture |volume=2 |issue=5 |pages=193–198 |year=1951 |last1=Fraser |first1=J. R }} 11. ^{{cite book|author=Madatally Manji|title=Memoirs of a biscuit baron|publisher= East African Publishers|year= 1995|pages=49–51|url=https://books.google.com/books?id=_D_dZZHkWGcC|isbn=9789966465023}} 3 : Wheat flour|Wheat|Flour |
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