The reduction of Ag + ions in ethanol when certain surfactants are also present in the solution is shown to take place, even in the total absence of light. The reduction process leads to dispersions of silver nanoparticles, which are stable for weeks, although they show a certain tendency to stick to glass walls. Several surfactants were tested, showing that there is a dependency on their nature and concentration. Nonionic ethoxylated surfactants proved to be the most effective of all the surfactants tested, the reduction then being due to the oxidation of oxyethylene groups. In any case, the yield is very low (around 1%).

Colloidal stability is achieved by adsorption of surfactant molecules onto the particles, which permits easy transfer of the particles into nonpolar solvents. The reduction rate markedly depends in a first-order fashion on silver salt concentration and depends on temperature according to Arrhenius's law. The optical properties of the obtained colloids are influenced by the surfactant molecules attached to the particle surface. Learn more about these metrics Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days. The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online.

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Various leavened breads Main ingredients, Bread is a prepared from a of and, usually. Throughout recorded history it has been popular around the world and is one of the oldest artificial foods, having been of importance since the dawn of. Proportions of types of flour and other ingredients vary widely, as do modes of preparation. As a result, types, shapes, sizes, and textures of breads differ around the world.

Bread may be by processes such as reliance on naturally occurring microbes, chemicals, industrially produced yeast, or high-pressure aeration. Some bread is cooked before it can leaven, including for traditional or religious reasons. Non-cereal ingredients such as fruits, nuts and fats may be included. Commercial bread commonly contains additives to improve flavor, texture, color, shelf life, and ease of manufacturing. Bread is served in various forms with any meal of the day. It is eaten as a snack, and used as an ingredient in other culinary preparations, such as sandwiches, and fried items coated in to prevent sticking. It forms the bland main component of, as well as of designed to fill cavities or retain juices that otherwise might drip out.

Bread has a social and emotional significance beyond its importance as nourishment. It plays essential roles in religious rituals and secular culture. Its prominence in daily life is reflected in language, where it appears in proverbs, colloquial expressions ('He stole the bread from my mouth'), in prayer ('Give us this day our daily bread') and in the etymology of words, such as ' (from com 'with' + panis 'bread'). Bread shop, from Northern Italy, beginning of the 15th century Bread is one of the oldest prepared foods.

Evidence from 30,000 years ago in Europe revealed starch residue on rocks used for pounding plants. It is possible that during this time, starch extract from the roots of plants, such as cattails and ferns, was spread on a flat rock, placed over a fire and cooked into a primitive form of flatbread. Around 10,000 BC, with the dawn of the age and the spread of agriculture, grains became the mainstay of making bread. Yeast spores are ubiquitous, including on the surface of, so any dough left to rest leavens naturally. There were multiple sources of available for early bread. Airborne yeasts could be harnessed by leaving uncooked dough exposed to air for some time before cooking.

Reported that the and used the foam skimmed from called to produce 'a lighter kind of bread than other peoples' such as. Parts of the ancient world that drank wine instead of beer used a paste composed of juice and flour that was allowed to begin fermenting, or wheat bran steeped in, as a source for.

The most common source of leavening was to retain a piece of dough from the previous day to use as a form of sourdough, as Pliny also reported. In 1961 the was developed, which used the intense mechanical working of dough to dramatically reduce the period and the time taken to produce a loaf. The process, whose high-energy mixing allows for the use of lower protein grain, is now widely used around the world in large factories. As a result, bread can be produced very quickly and at low costs to the manufacturer and the consumer. However, there has been some criticism of the effect on nutritional value.

Brown bread (left) and whole grain bread Bread is the staple of the,,, and in European-derived cultures such as those in the,, and, in contrast to East Asia where is the staple. Bread is usually made from a - that is cultured with yeast, allowed to rise, and finally baked in an. The addition of yeast to the bread explains the air pockets commonly found in bread. Owing to its high levels of (which give the dough sponginess and elasticity), is the most common grain used for the preparation of bread, which makes the largest single contribution to the world's food supply of any food. Bread is also made from the flour of other wheat species (including,, and ).

Non-wheat cereals including,, (corn),,, and have been used to make bread, but, with the exception of rye, usually in combination with wheat flour as they have less gluten. Have been created for people affected by such as and, who may benefit from a. Gluten-free bread is made with ground flours from a variety of materials such as almonds, rice, sorghum, corn, or legumes such as beans, but since these flours lack gluten they may not hold their shape as they rise and their crumb may be dense with little aeration. Additives such as xanthan gum, guar gum, hydroxypropyl methylcellulose (HPMC), corn starch, or eggs are used to compensate for the lack of gluten. Properties Physical-chemical composition In, compounds are mainly found in in the form of insoluble bound, where it is relevant to wheat resistance to fungal diseases. Contains and. Three glucosides,, and, can be found in commercial breads containing.

And are functional proteins found in wheat bread that contribute to the structure of bread. Glutenin forms interconnected gluten networks within bread through interchain disulfide bonds. Gliadin binds weakly to the gluten network established by glutenin via intrachain disulfide bonds. Structurally, bread can be defined as an elastic-plastic (same as ). The glutenin protein contributes to its nature, as it is able to regain its initial shape after deformation.

The gliadin protein contributes to its nature, because it demonstrates non-reversible structural change after a certain amount of applied force. Because air pockets within this gluten network result from carbon dioxide production during leavening, bread can be defined as a foam, or a gas-in-solid solution.

Culinary uses. Bread can be served at many; once baked, it can subsequently be. It is most commonly eaten with the hands, either by itself or as a carrier for other foods. Bread can be dipped into liquids such as,, or; it can be topped with various sweet and savory spreads, or used to make containing, cheeses, vegetables, and. Bread is used as an ingredient in other culinary preparations, such as the use of to provide crunchy crusts or thicken sauces, sweet or savoury, or as a binding agent in and other ground meat products. Nutritional significance Nutritionally, bread is known as an ample source for the grains category of nutrition. Serving size of bread is standard in the USA through ounces, counting one slice of bread (white processed bread) as 1 oz.

Also, bread is considered a good source of carbohydrates through the whole grains, nutrients such as magnesium, iron, selenium, B vitamins, and dietary fiber. Crust The bread crust is formed from surface dough during the cooking process. It is hardened and browned through the using the sugars and amino acids and the intense heat at the bread surface. The crust of most breads is harder, and more complexly and intensely flavored, than the rest. Suggest that eating the bread crust makes a person's hair curlier. Additionally, the crust is rumored to be healthier than the rest.

Some studies have shown that this is true as the crust has more and such as, which is being researched for its potential inhibitory properties. Baking bread in Formulation Professional bread recipes are stated using the notation.

The amount of flour is denoted to be 100%, and the other ingredients are expressed as a percentage of that amount by weight. Measurement by weight is more accurate and consistent than measurement by volume, particularly for dry ingredients.

The proportion of water to flour is the most important measurement in a bread recipe, as it affects texture and crumb the most. Hard wheat flours about 62%, while softer wheat flours absorb about 56%. Common table breads made from these doughs result in a finely textured, light bread. Most artisan bread formulas contain anywhere from 60 to 75% water. In yeast breads, the higher water percentages result in more CO 2 bubbles and a coarser bread crumb. One pound (450 ) of flour yields a standard loaf of bread or two loaves.

Is commonly added by commercial bakeries to retard the growth of molds. Main article: is grain ground to a powdery consistency. Flour provides the primary structure, starch and protein to the final baked bread. The content of the flour is the best indicator of the quality of the bread and the finished bread. While bread can be made from all-purpose wheat flour, a specialty bread flour, containing more protein (12–14%), is recommended for high-quality bread.

If one uses a flour with a lower protein content (9–11%) to produce bread, a shorter mixing time is required to develop gluten strength properly. An extended mixing time leads to oxidization of the dough, which gives the finished product a whiter crumb, instead of the cream color preferred by most artisan bakers. Wheat flour, in addition to its starch, contains three water-soluble protein groups (,, and ) and two water-insoluble protein groups ( and ).

When flour is mixed with water, the water-soluble proteins dissolve, leaving the glutenin and gliadin to form the structure of the resulting bread. When relatively dry dough is worked by, or wet dough is allowed to rise for a long time (see ), the glutenin forms strands of long, thin, chainlike molecules, while the shorter gliadin forms bridges between the strands of glutenin. The resulting networks of strands produced by these two proteins are known as. Gluten development improves if the dough is allowed to. Liquids Water, or some other liquid, is used to form the flour into a paste or dough.

The weight of liquid required varies between recipes, but a ratio of 3 parts liquid to 5 parts flour is common for yeast breads. Recipes that use steam as the primary leavening method may have a liquid content in excess of 1 part liquid to 1 part flour. Instead of water, recipes may use liquids such as milk or other (including or ), fruit juice, or eggs. These contribute additional sweeteners, fats, or leavening components, as well as water. Fats or shortenings Fats, such as butter, vegetable oils, lard, or that contained in eggs, affect the development of gluten in breads by coating and lubricating the individual strands of protein.

They also help to hold the structure together. If too much fat is included in a bread dough, the lubrication effect causes the protein structures to divide. A fat content of approximately 3% by weight is the concentration that produces the greatest leavening action. In addition to their effects on leavening, fats also serve to tenderize breads and preserve freshness. Medina County Cauv Program Ohio on this page. Bread improvers. Main article: and are often used in producing commercial breads to reduce the time needed for rising and to improve texture and volume. The substances used may be oxidising agents to strengthen the dough or reducing agents to develop gluten and reduce mixing time, emulsifiers to strengthen the dough or to provide other properties such as making slicing easier, or enzymes to increase gas production.

Salt is often added to enhance flavor and restrict yeast activity. It also affects the crumb and the overall texture by stabilizing and strengthening the gluten. Some artisan bakers forego early addition of salt to the dough, whether wholemeal or refined, and wait until after a 20-minute rest to allow the dough to. A dough trough once used for leavening bread from Aberdour Castle, Fife, Scotland. Is the process of adding gas to a dough before or during baking to produce a lighter, more easily chewed bread. Most bread eaten in the West is leavened.

Chemicals A simple technique for leavening bread is the use of gas-producing chemicals. There are two common methods. Hp Anatel Wireless Keyboard Driver. The first is to use or a that includes baking powder. The second is to include an acidic ingredient such as and add; the reaction of the acid with the soda produces gas. Chemically leavened breads are called and.

This method is commonly used to make,, American-style, and quick breads such as. Sourdough loaves Sourdough is a type of bread produced by a long fermentation of dough using naturally occurring yeasts and. It usually has a mildly sour taste because of the produced during by the lactobacilli. Sourdough breads are made with a sourdough starter. The starter cultivates yeast and lactobacilli in a mixture of flour and water, making use of the microorganisms already present on flour; it does not need any added yeast. A starter may be maintained indefinitely by regular additions of flour and water.

Some bakers have starters many generations old, which are said to have a special taste or texture. At one time, all yeast-leavened breads were sourdoughs. Recently there has been a revival of sourdough bread in artisan bakeries. Traditionally, peasant families throughout Europe baked on a fixed schedule, perhaps once a week. The starter was saved from the previous week's dough. The starter was mixed with the new ingredients, the dough was left to rise, and then a piece of it was saved (to be the starter for next week's bread). Steam The rapid expansion of steam produced during baking leavens the bread, which is as simple as it is unpredictable.

Steam-leavening is unpredictable since the steam is not produced until the bread is baked. Steam leavening happens regardless of the raising agents (baking soda, yeast, baking powder, sour dough, beaten egg white) included in the mix. The leavening agent either contains air bubbles or generates carbon dioxide. The heat vaporises the water from the inner surface of the bubbles within the dough. The steam expands and makes the bread rise.

This is the main factor in the rising of bread once it has been put in the oven. Generation, on its own, is too small to account for the rise. Heat kills bacteria or yeast at an early stage, so the CO 2 generation is stopped. Bacteria employs a form of bacterial leavening that does not require yeast. Although the leavening action is inconsistent, and requires close attention to the incubating conditions, this bread is making a comeback for its cheese-like flavor and fine texture. Aeration was leavened by carbon dioxide being forced into dough under pressure. From the mid 19th to mid 20th centuries bread made this way was somewhat popular in the United Kingdom, made by the and sold in its high-street.

The company was founded in 1862, and ceased independent operations in 1955. The Pressure-Vacuum mixer was later developed by the Flour Milling and Baking Research Association for the. It manipulates the gas bubble size and optionally the composition of gases in the dough via the gas applied to the headspace. The organic baker Andrew Whitely, writing in, called the process 'the covert corruption of our daily food'. Cultural significance.

Main article: because of its history and contemporary importance. Bread is also as one of the elements (alongside ) of the, and in other religions including. In many cultures, bread is a for basic necessities and living conditions in general.

For example, a 'bread-winner' is a household's main economic contributor and has little to do with actual bread-provision. This is also seen in the phrase 'putting bread on the table'. The Roman poet satirized superficial politicians and the public as caring only for ' panem et circenses' (). In in 1917, the Bolsheviks promised 'peace, land, and bread.'

The term ' denotes an agriculturally productive region. In cultures is offered as a welcome to guests. In, life's basic necessities are often referred to as 'roti, kapra aur makan' (bread, cloth, and house). Words for bread, including 'dough' and 'bread' itself, are used in -speaking countries as for. A remarkable or revolutionary innovation may be called the best thing since '. The expression 'to break bread with someone' means 'to share a meal with someone'.

The English word 'lord' comes from the Anglo-Saxon hlāfweard, meaning 'bread keeper.' • Kaplan, Steven Laurence: Good Bread is Back: A Contemporary History of French Bread, the Way It Is Made, and the People Who Make It. Durham/ London: Duke University Press, 2006. • Jacob, Heinrich Eduard: Six Thousand Years of Bread. Its Holy and Unholy History. Garden City / New York: Doubleday, Doran and Comp., 1944. New 1997: New York: Lyons & Burford, Publishers (Foreword by Lynn Alley), < • Spiekermann, Uwe: Brown Bread for Victory: German and British Wholemeal Politics in the Inter-War Period, in: Trentmann, Frank and Just, Flemming (ed.): Food and Conflict in Europe in the Age of the Two World Wars.

Basingstoke / New York: Palgrave, 2006, pp. 143–171, • Cunningham, Marion (1990). The Fannie Farmer cookbook. Illustrated by Lauren Jarrett (13th ed.). • Trager, James (1995). The food chronology: a food lover's compendium of events and anecdotes from prehistory to the present.

• Davidson, Alan (1999). The Oxford Companion to Food.

Oxford University Press.. Samuel (2000).

'Brewing and baking'. Nicholson; I. Ancient Egyptian materials and technology. Cambridge: Cambridge University Press. Baking Science & Technology 3rd Ed. Sosland Publishing Company.. External links • at Wikibook Cookbooks • travel guide from Wikivoyage.