Bread is a staple food prepared from a dough of flour and water, usually by baking. Throughout recorded history it has been a prominent food in large parts of the world. It is one of the oldest man-made foods, having been of significant importance since the dawn of agriculture, and plays an essential role in both religious rituals and secular culture.

Bread may be leavened by naturally occurring microbes, chemicals, industrially produced yeast, or high-pressure aeration. In many countries, commercial bread often contains additives to improve flavor, texture, color, shelf life, nutrition, and ease of production.

Etymology of bread
The Old English word for bread was hlaf (hlaifs in Gothic: modern English loaf), which appears to be the oldest Teutonic name. Old High German hleib and modern German Laib derive from this Proto-Germanic word, which was borrowed into Slavic (Polish chleb, Russian khleb) and Finnic (Finnish leipä, Estonian leib) languages as well. The Middle and Modern English word bread appears in Germanic languages, such as West Frisian brea, Dutch brood, German Brot, Swedish bröd, and Norwegian and Danish brød; it may be related to brew or perhaps to break, originally meaning "broken piece", "morsel".

History of bread
Bread is one of the oldest prepared foods. Evidence from 30,000 years ago in Europe and Australia 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. The world's oldest evidence of bread-making has been found in a 14,500-year-old Natufian site in Jordan's northeastern desert. Around 10,000 BC, with the dawn of the Neolithic age and the spread of agriculture, grains became the mainstay of making bread. Yeast spores are ubiquitous, including on the surface of cereal grains, so any dough left to rest leavens naturally.

There were multiple sources of leavening available for early bread. Airborne yeasts could be harnessed by leaving uncooked dough exposed to air for some time before cooking. Pliny the Elder reported that the Gauls and Iberians used the foam skimmed from beer called barm to produce "a lighter kind of bread than other peoples" such as barm cake. Parts of the ancient world that drank wine instead of beer used a paste composed of grape juice and flour that was allowed to begin fermenting, or wheat bran steeped in wine, as a source for yeast. The most common source of leavening was to retain a piece of dough from the previous day to use as a form of sourdough starter, as Pliny also reported.

The Chorleywood bread process was developed in 1961; it uses the intense mechanical working of dough to dramatically reduce the fermentation period and the time taken to produce a loaf. The process, whose high-energy mixing allows for the use of grain with a lower protein content, 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.

Types of bread
Bread is the staple food of the Middle East, Central Asia, North Africa, Europe, and in European-derived cultures such as those in the Americas, Australia, and Southern Africa, in contrast to parts of South and East Asia where rice or noodle is the staple. Bread is usually made from a wheat-flour dough that is cultured with yeast, allowed to rise, and finally baked in an oven. The addition of yeast to the bread explains the air pockets commonly found in bread. Owing to its high levels of gluten (which give the dough sponginess and elasticity), common or bread wheat 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.


Strucia — a type of European sweet bread
Bread is also made from the flour of other wheat species (including spelt, emmer, einkorn and kamut). Non-wheat cereals including rye, barley, maize (corn), oats, sorghum, millet and rice have been used to make bread, but, with the exception of rye, usually in combination with wheat flour as they have less gluten.

Gluten-free breads are made using ground flours from a variety of ingredients such as almonds, rice, sorghum, corn, or legumes such as beans, and tubers such as cassava, 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 of bread
In wheat, phenolic compounds are mainly found in hulls in the form of insoluble bound ferulic acid, where it is relevant to wheat resistance to fungal diseases.

Rye bread contains phenolic acids and ferulic acid dehydrodimers.

Three natural phenolic glucosides, secoisolariciresinol diglucoside, p-coumaric acid glucoside and ferulic acid glucoside, can be found in commercial breads containing flaxseed.


Small home made bread with pumpkin and sunflower seeds
Glutenin and gliadin 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 foam (same as styrofoam). The glutenin protein contributes to its elastic nature, as it is able to regain its initial shape after deformation. The gliadin protein contributes to its plastic 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.

Acrylamide, like in other starchy foods that have been heated higher than 120 °C (248 °F), has been found in recent years to occur in bread. Acrylamide is neurotoxic, has adverse effects on male reproduction and developmental toxicity and is carcinogenic. A study has found that more than 99 percent of the acrylamide in bread is found in the crust.