infusion and tea

Infusion
Infusion is the process of extracting chemical compounds or flavors from plant material in a solvent such as water, oil or alcohol, by allowing the material to remain suspended in the solvent over time (a process often called steeping).  An infusion is also the name for the resultant liquid.

A common example of an infusion is tea, and many tisanes are prepared in the same way.  Lemon, chamomile, senna, apple, ginger, rooibos, and a great many other plants are used individually or in combination.  Herbal infusions in water and oil are both commonly used as herbal remedies.  Coffee can also be made through infusion (as in a French press), but it is more often made through percolation.

Tisane
Tisane or "herbal tea" is a catch-all term for any non-caffeinated beverage made from the infusion or decoction of herbs, spices, or other plant material.  These drinks are distinguished from caffeinated  beverages like coffee, maté, and the true teas (black, green, white, yellow, oolong, etc.), or from a decaffeinated tea, in which the caffeine has been removed.  In addition to serving as a beverage, many tisanes are also consumed due to a perceived medicinal benefit.

Like brews made from the tea bush (Camellia sinensis), such infusions are prepared by combining hot water and fruits, leaves, roots or grains.

Tisanes can be made with fresh or dried flowers, leaves, seeds or roots, generally by pouring boiling water over the plant parts and letting them steep for a few minutes.  Seeds and roots can also be boiled on a stove.  The tisane is then strained, sweetened if so desired, and served.  Many companies produce herbal tea bags for such infusions.

Flavored teas are prepared by adding other plants to an actual tea (black, oolong, green, yellow or white tea); for example, the popular Earl Grey tea is black tea with bergamot (the orange oil, not the herb of the same name), jasmine tea is Chinese tea with jasmine flowers, and genmaicha is a Japanese green tea with toasted rice.

Tea
Tea is an aromatic beverage commonly prepared by pouring hot or boiling water over cured leaves of the tea plant, Camellia sinensis.  After water, tea is the most widely consumed beverage in the world.  It has a cooling, slightly bitter, astringent flavor, which many people enjoy.

The phrase "herbal tea" usually refers to infusions of fruit or herbs made without the tea plant, such as rosehip tea or chamomile tea.  Alternative phrases for this are tisane or herbal infusion, both bearing an implied contrast with "tea" as it is construed here.

Although single estate teas are available, almost all teas in bags and most other teas sold in the West are blends.  Blending may occur in the tea-planting area (as in the case of Assam), or teas from many areas may be blended.  The aim of blending is to obtain better taste, higher price, or both, as a more expensive, better-tasting tea may cover the inferior taste of cheaper varieties.

Some teas are not pure varieties, but have been enhanced through additives or special processing.  Tea is highly receptive to inclusion of various aromas; this may cause problems in processing, transportation, and storage, but also allows for the design of an almost endless range of scented and flavored variants, such as bergamot (Earl Grey), vanilla, and caramel.

FURTHER READING

Caffeine
Caffeine is a bitter, white crystalline xantine alkaloid that acts as a stimulant drug.  Caffeine is found in varying quantities in the seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants.  It is most commonly consumed by humans in infusions extracted from the seed of the coffee plant and the leaves of the tea bush, as well as from various foods and drinks containing products derived from the kola nut.  Other sources include yerba maté, guarana berries, guayusa, and the yaupon holly.

In humans, caffeine acts as a central nervous system stimulant, temporarily warding off drowsiness and restoring alertness.

Percolation Percolation concerns the movement and filtering of fluids through porous materials.

In coffee percolation, soluble compounds leave the coffee grounds and join the water to form coffee. These soluble compounds are the chemical compounds that give coffee its color, taste, and aroma. Insoluble compounds remain within the coffee filter.

Decoction
Decoction is a method of extraction by boiling, of dissolved chemicals, from herbal or plant material, which may include stems, roots, bark and rhizomes. Decoction involves first mashing, and then boiling in water to extract oils, volatile organic compounds, and other chemical substances. Decoction can be used to make tisanes, teas, coffees, tinctures and similar solutions. Decoctions and infusions may produce liquids with differing chemical properties, as the temperature/preparation difference may result in more oil-soluble chemicals in decoctions vs infusions. The process can also be applied to meats and vegetables to prepare bouillon or stock.

A decoction is also the name for the resulting liquid. Although this method of extraction differs from infusion and percolation, the resultant liquids are often functionally similar.

Alkaloids
Alkaloids are a group of naturally occurring chemical compounds, that contain mostly basic nitrogen atoms.  They are produced by a large variety of organisms, including bacteria, fungi, plants, and animals, and are part of the group of natural products.

Sources:

http://en.wikipedia.org/wiki/Infusion
http://en.wikipedia.org/wiki/Tisane
http://en.wikipedia.org/wiki/Tea
http://en.wikipedia.org/wiki/Caffeine
http://en.wikipedia.org/wiki/Percolation
http://en.wikipedia.org/wiki/Decoction
http://en.wikipedia.org/wiki/Alkaloid