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Plant Product Project: Flour -- SBI3U-04
Transcript of Plant Product Project: Flour -- SBI3U-04
SBI3U-04 Information on the plant, wheat, which is the main ingredient of flour. Plant Biology Species: during the 10 000 years of cultivation, numerous forms of wheat have evolved under human selection. This diversity has led to much confusion in the naming of wheat species, including many species and subspecies. Scientific Classification Speciation: After millennia of hybridization and modification by humans, different wheats can have different ploidy levels: diploid (2n), tetraploid (4n), and hexaploid (6n). Polyploid cells and organisms are those containing more than two paired (homologous) sets of chromosomes. This is important as to the speciation of the plant; the species that share the same ploidy level are closest to one another.
**Included on the previous table are certain hybrid species, and mutants which have only occurred in laboratory experiments.
The presence of certain versions of wheat genes has been important for crop yields. Over the years there have been incredible advances in wheat breeding. For example, the deliberate selection of alleles that affect growth characteristics, has led to short-stalked wheat. Genes for the 'dwarfing' trait, produce short-stalked wheat, which enable the carbon that is fixed in the plant during photosynthesis to be diverted towards seed production, as opposed to be lost toward apical growth and transportation. The physical appearance of the grain is familiar to most consumers, with a long stalk that terminates in a tightly formed cluster of plump kernels enclosed by a beard of bristly spikes.
Humans have cultivated wheat for hundreds of years, and as a result, the wheat we see today probably looks very different Physical Appearance from the the wheat our ancestors. The early wheat-breeders would have wanted to select for plants with particularly large kernels, since more nutrition could be eked out from each stalk. Plant Product: flour Uses of Flour Technology Physical Appearance... continued - Wheat attains an average height of 1.2 m (4 ft).
- The leaves are followed by slender stalks terminating in spikes, or so-called ears, of grain.
- As a monocot angiosperm, wheat has the physical characteristics that this entails:
- Only one cotyledon
- Single seed leaf
- Scattered vascular bundles
-Parallel veins (closeup )
-Fibrous roots (See previous diagram) Plant Growth Wheat is an annual, meaning it completes its entire life cycle from seed to reproduction to death in one year. It is also a long-day plant, meaning it flowers when the day length exceeds their critical photoperiod. In the northern hemisphere, this happens mid-June (roughly the 21st).
Spring wheat is planted throughout Canada from May to June, and harvested from August to October. All durum wheat in Canada is spring wheat. Winter wheat is planted from September to November in eastern Canada and along the U.S. border in the Prairie provinces. Winter wheat is harvested in July and August. Plant Reproduciton Wheat is a part of the angiosperm division of plants. This means it follows the typical alternation of generations: Although the wheat plant does not have very noticeable petaled blossoms as used in the video, they do still have very small flowers among the kernels on the head of the wheat stalk. Because wheat is generally a self pollinating plant, when farmers want to hybridize a strain, they must physically pollinate the different plants. Common Types of Flour What is flour made of ? All-Purpose: All-purpose flour is made from the endosperm of wheat. All-purpose flour has a medium balance of starch and protein so that it can be used in a wide variety of products without being too heavy or too delicate.
Unbleached: Unbleached flour is similar in composition to all-purpose flour but has not been chemically bleached.
Bread Flour: Bread flour contains a higher ratio of protein to carbohydrates than all-purpose, which produces stronger dough. The strong gluten matrix provides structure to rising dough and gives the end product a nice, chewy texture.
Cake Flour: Cake flour contains less protein than all-purpose and is milled to a finer texture. These two factors combined create a softer and more delicate crumb. Cake flour is often bleached to improve its appearance.
Pastry Flour: Pastry flour has a medium protein content and is between all-purpose and cake flour in texture. The fine texture produces flakey pastry crust while the slightly lower protein content prevents pastries from being too dense or chewy.
Self-Rising: Self-rising flour is mainly used to make biscuits and other quick breads. It is comprised of all-purpose flour, salt and a chemical leavening agent such as baking powder. Self-rising flour should never be used to make yeast breads.
Whole Wheat: Whole wheat flour is made by grinding the entire grain (endosperm, bran and germ). This flour contains more nutrients and fibre than all-purpose, producing a heavier, denser bread than all-purpose or bread flours.
Stone Ground: Stone ground flour is the same as whole wheat flour but is milled to a coarser texture. Stone ground flour is valued for its distinctive rough texture and rustic look.
Semolina: Semolina is flour made from a specific variety of wheat known as Durum. Durum wheat has an exceptionally high protein content, giving it a very dense, chewy texture. For this reason, semolina is most often used to make pasta. Flower is one of the main ingredients in most prepared foods today, and a main staple in the global diet. Almost anything that is baked, contains flour: wheat is the major ingredient in most breads, rolls, crackers, cookies, biscuits, cakes, doughnuts, muffins, pancakes, waffles, noodles, piecrusts, ice cream cones, macaroni, spaghetti, puddings, pizza, and many prepared hot and cold breakfast foods. The part of the wheat plant that is actually ground up to make flour is the grain -- the seed. Each grain of wheat is made up of three distinct parts:
First there is the coarse outer bran layer. Inside the bran layer the grain is made up of two main parts; the germ (the embryo of the plant) and the endosperm. Wheat germ is a concentrated source of several essential nutrients including Vitamin E, fibre, folate (folic acid), phosphorus, thiamin, zinc, and magnesium. It is also is rich in polyunsaturated fats. It is these fats that, upon improper storage can undergo oxidative rancidification -- where fatty acids decompose into aldehydes and keytones. Rancid flour has the potential to make those eating it very ill. To prevent this, flour should ideally be kept in a sealed container in a cool, dry, and dark location. What makes wheat flour special? One of the main differences between the different types of flour is the gluten content. Found in the protein of wheat, gluten is responsible for the elasticity in bread, and other food products. It forms when glutenin molecules cross-link to form a sub-microscopic network attached to gliadin, which contributes viscosity and extensibility to the dough of bread. If this dough is leavened with yeast, fermentation produces carbon dioxide bubbles, which, trapped by the gluten network, cause the dough to rise. Baking coagulates the gluten, which, along with starch, stabilizes the shape of the final product.
The development of gluten (i.e., enhancing its elasticity) affects the texture of the baked goods. More refining leads to chewier products such as pizza dough and bagels, while less refining yields tender baked goods such as pastry products.
Generally, bread flours are high in gluten (hard wheat); pastry flours have a lower gluten content. Kneading promotes the formation of gluten strands and cross-links, creating baked products that are chewier in proportion to the length of kneading.
The strength and elasticity of gluten in flour is measured in the baking industry using a farinograph. This gives the baker a measurement of quality for different varieties of flours in developing recipes for various baked goods. Technological advances in soil preparation and seed placement at planting time, use of crop rotation and fertilizers to improve plant growth, and advances in harvesting methods have all combined to promote wheat as a viable crop. Agricultural cultivation using horse collar leveraged plows (at about 3000 BCE) was one of the first innovations that allowed for the production of flour. discovered that a more edible product could be made by separating the ground meal into coarse bran particles and white flour. The advent of weaving made this process possible. Sieves or baskets were made using horse hair or papyrus. Later, Ancient Romans ground and sifted the flour through linen, twice . This was an expensive procedure that only the aristocracy could afford. It is thought that the Romans were the first to have started a milling industry using animals or teams of slaves to drive the wheels to grind the wheat. Before this, grinding of meal had mostly been carried out in the home using a device called a hand-quern. The hand-quern consisted of two round flat stones, one above the other. The upper stone was turned by a wooden handle, wheat was trickled in through a hole in the centre, and meal came out around the edge.
Gradual developments in milling techniques, especially the introduction of the rotary mill around 1000BC, meant improvements in flour for baking. Eventually in the 11th Century watermills and windmills enabled real progress.
Most of the common machines, such as the roller mill, were developed by the 1900s and are still in use in present-day mills.
Much later, when the use of seed drills replaced broadcasting sowing of seed in the 18th century, another great increase in productivity occurred. Yields of wheat per unit area increased as methods of crop rotation were applied to long cultivated land, and the use of fertilizers became widespread. Improved agricultural husbandry has more recently included threshing machines and reaping machines (the 'combine harvester'), tractor-drawn cultivators and planters, and better varieties (see Green Revolution and Norin 10 wheat). Great expansion of wheat production occurred as new arable land was farmed in the Americas and Australia in the 19th and 20th centuries. One of the oldest technologies for making flour is the combination of a stone mortar and pestle to initially break the grain, and the saddle quern for grinding it. The saddle quern is an elongated stone with a depression in it where the grain is placed, and then a woman (it was usually a woman) kneels in front of the short end and pushes a smaller stone back and forth over the grain in a rocking motion. It takes a long time to make any useful amount of flour in this manner. In fact, archaeologists examining women’s bones from a Neolithic site in what is now Northern Syria, found many of the women had deformities to their toes, legs, back, and pelvis which can be attributed to spending many hours kneeling in front of a saddle quern. The next development is the rotary quern which consists of two round stones placed on top of each other. The lower stone is slightly convex, and the upper, concave. The top stone has a vertical handle coming from it’s top and a hole in the middle where the grain is fed. The operator (also most likely a woman) uses the handle to turn the top stone, grinding the grain between the stones. The finished flour flows out from between the edges of the stones. Some versions included a spout which would feed the finished flour out into a container. Here’s a great video of someone operating a rotary quern. That still looks like an awful lot of work to get enough flour to make a loaf of bread. The ancient Greeks and Romans made some important contributions to grain milling technology: The Romans built larger versions of the rotary quern and used animals or slaves to drive them. The ancient Greeks invented the first water mill, comprising of a wooden shaft extending down into a stream, and a horizontal water wheel was placed on top. The water's current turned top stone grinding the grain. Eventually the Romans stood the wheel on its side, and used gears to transfer the power of the water to the grinding stones. This configuration: a vertical wheel, gears, and two grinding stones working in a rotary manner, remained the predominant method of milling flour until roller mills were introduced in Europe in the 19th Century. There were some changes as to how the stone mills were configured and powered, but essentially the technology was the same for almost 2000 years. Roman Water Wheel Windmills function along the same principles, where the wind rotates sails, turning gears. DutchWindmill