Starch
A polysaccharide energy store in plants and human staple.
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Starch is a polysaccharide made of many glucose molecules linked by glycosidic bonds. Most green plants produce it to store energy. It is the most widely consumed carbohydrate in human diets around the world, appearing in large amounts in staple foods like wheat, potatoes, corn, rice, and cassava. As a substance, starch is a white, tasteless, odorless powder that does not dissolve in cold water or alcohol.
It is made up of two kinds of molecules: linear, helical amylose and branched amylopectin. In most plants, starch is roughly 20–25% amylose and 75–80% amylopectin by weight. The animal energy reserve glycogen is a more highly branched version of amylopectin. Industrially, starch is often turned into sugars, such as through malting.
These sugars can then be fermented to produce ethanol for beer, whisky, and biofuel. Sugars from processed starch also appear in many processed foods. Mixing most starches with warm water creates a paste, like wheatpaste, which can thicken, stiffen, or glue things. The main non-food industrial use of starch is as an adhesive in papermaking.
Etymology
A similar paste, known as laundry starch, can be applied to textiles before ironing to stiffen them. The word "starch" comes from a Germanic root meaning "strong, stiff, strengthen, stiffen." Modern German Stärke (meaning both strength and starch) refers to its historical use in textiles—sizing yarn for weaving and starching linen. The Greek term amylon (ἄμυλον), meaning "not milled," gives the root "amyl," used as a prefix for starch-related carbon compounds like amyl alcohol, amylose, and amylopectin.
History
Starch grains from cattail rhizomes used as flour have been found on grinding stones in Europe dating back 30,000 years. Sorghum starch grains were found on grind stones in caves in Ngalue, Mozambique, dating up to 100,000 years ago. In Ancient Egypt, pure extracted wheat starch paste was likely used to glue papyrus. The extraction of starch was first described by Pliny the Elder around 77–79 CE.
Romans used it in cosmetic creams, hair powder, and to thicken sauces. Persians and Indians used it to make dishes similar to wheat halva. In China, rice starch has been used as a surface treatment for paper since 700 CE. By the mid-eighth century, paper sized with wheat starch was being produced in the Arabic world.
Quick Facts
- Field
- Carbohydrate chemistry
- plant biology
- food science
- Composition
- 20–25% amylose, 75–80% amylopectin
- Common sources
- Wheat
- potatoes
- maize
- rice
- cassava
Facts from the source article.
Lore & Background
Pure extracted wheat starch paste was used in Ancient Egypt, possibly to glue papyrus. The extraction of starch is first described in Pliny the Elder's Natural History around 77–79 CE. Romans used starch in cosmetic creams, to powder hair, and to thicken sauces. Laundry starch was first described in England in the mid-16th century and was essential for 16th-century ruffed collars.
Reader's Guide
Starch is fundamental to human civilization as both a dietary staple and an industrial material. As the most common carbohydrate in human diets, it provides energy from major crops like wheat, rice, and potatoes. Industrially, starch is converted into sugars for fermentation into ethanol for beer, whisky, and biofuel, and is used as a thickening, stiffening, or gluing agent. Its non-food uses include adhesive in papermaking and laundry starch for textiles.
The word 'starch' derives from a Germanic root meaning 'strong, stiff,' reflecting its historical use in textiles. The Greek term 'amylon' (not milled) provides the root 'amyl' for related compounds. Starch's structure—linear amylose and branched amylopectin—determines its properties; waxy starches (pure amylopectin) undergo less retrogradation, while high-amylose starches are used for gel strength and as resistant starch. The biosynthesis and degradation of starch in plants involve complex enzymatic pathways, with transitory starch in leaves providing energy at night.
Frequently Asked Questions
Who is Starch?
Starch is a polysaccharide carbohydrate that green plants synthesize to bank up energy for later use. It is built from long chains of glucose molecules linked together through glycosidic bonds.
What is Starch's role in the plant world?
In most green plants, starch serves as the primary way to store surplus energy produced during photosynthesis. It acts as a readily accessible fuel reserve that the plant can break down when it needs power for growth or reproduction.
What is Starch composed of?
Starch is a blend of two distinct glucose-based polymers: amylose, which makes up roughly 20–25% of the total, and amylopectin, which accounts for the remaining 75–80%. The two differ mainly in how their sugar chains are branched.
Where do people encounter Starch in everyday life?
Starch shows up in staple crops around the globe, including wheat, potatoes, maize, rice, and cassava. It also finds wide use outside the kitchen, for example as a binding agent in industrial adhesives.
More in Botany & Plant Biology
Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Starch (CC BY-SA 4.0).
- Word definitions: the Codexery glossary, each quoted from its Wikipedia article.
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