question: Why do hot drinks like coffee or tea taste so much different (worse) once they've gone from hot to room-temp?
comment: It's more than just temperature, at least for coffee. When coffee is left sitting out, more than just the water evaporates. Many of the compounds that give coffee its flavor also evaporate readily at room temperatures. Once these start to evaporate, the taste of the coffee is changed for the worse. Iced coffee will taste much better than if you were to add ice to brewed coffee that has been allowed to cool on the counter. It's because the compounds haven't had a chance to evaporate in the iced coffee, allowing it to keep its flavour more than the cooled coffee.
passages: Brewed coffee, if kept hot, will deteriorate rapidly in flavor, and reheating such coffee tends to give it a "muddy" flavour, as some compounds that impart flavor to coffee are destroyed if this is done. Even at room temperature, deterioration will occur; however, if kept in an oxygen-free environment it can last almost indefinitely at room temperature, and sealed containers of brewed coffee are sometimes commercially available in food stores in America or Europe, with refrigerated bottled coffee drinks being commonly available at convenience stores and grocery stores in the United States. Canned coffee is particularly popular in Japan and South Korea.
   Water temperature is subtler but crucial to the proper extraction of flavor from the ground coffee, as it affects the proportions in which solubles are extracted – one wishes to extract the desired flavors as much as possible, and the undesirable flavors as little as possible. The recommended brewing temperature range of coffee is 91–94 °C (195–202 °F), which is a trade-off between these goals. If cooler, some of the solubles that make up the flavor will not be extracted. If the water is too hot, some undesirable, bitter, elements will be extracted, adversely affecting the taste. Note that this desired temperature range is slightly below the boiling point of water (100 °C or 212 °F at standard pressure), so coffee is best made with water that has been allowed to come off the boil slightly. Another consideration is the difference between the temperature of the water and the temperature of the coffee slurry: for example, certain brewing methods (e.g., manual pourover) can result in losing a significant amount of heat to the atmosphere during the brewing process.
   Transient temperature is not very significant: if coffee is heated to boiling point only very briefly, the taste will be little affected; the longer it is kept at a high temperature the worse the taste becomes.
  
  Section::::Strength.
   Because the ground coffee beans in cold-brewed coffee never come into contact with heated water, the process of leaching flavor from the beans produces a chemical profile different from conventional brewing methods. Coffee beans contain a number of constituent parts that are more soluble at higher temperatures, such as caffeine, oils and fatty acids. Brewing at a lower temperature results in lower acidity and lower caffeine content when brewed in equal volume. It is around 65 to 70 percent less acidic than hot drip coffee or espresso, per part. Although less caffeine is extracted with the cold brew method, a higher coffee-to-water ratio is often used, between 2 and 2 1/2 times. This may compensate for this difference in solubility, resulting in a brew with equal, if not more, caffeine (although this is unlikely).
   While most tea is prepared using hot water, it is also possible to brew a beverage from tea using room temperature or cooled water. This requires longer steeping time to extract the key components, and produces a different flavour profile. Cold brews use about 1.5 times the tea leaves that would be used for hot steeping, and are refrigerated for 4–10 hours. The process of making cold brew tea is much simpler than that for cold brew coffee.
   As the brew continually seeps through the grounds, the overall temperature of the liquid approaches boiling point, at which stage the "perking" action (the characteristic spurting sound the pot makes) stops, and the coffee is ready for drinking. In a manual percolator it is important to remove or reduce the heat at this point. Brewed coffee left on high heat for too long will acquire a bitter taste.
   The water is normally kept at room temperature, but chilled water is also used. The grounds are filtered out of the water after they have been steeped using a paper coffee filter, a fine metal sieve, a French press, or felt, in the case of the "Toddy" brewing system. The result is a coffee concentrate that is diluted with water or milk, and is served hot, over ice, or blended with ice and other ingredients such as chocolate. 
   Many coffee retailers simply use hot-brewed coffee in their iced coffee drinks. Starbucks specifically uses the double-strength method in which the coffee is brewed hot with twice the amount of grounds. With this method, the melted ice does not dilute the strength and flavour of the coffee. Unlike the cold-brew process, this method does not eliminate the acidity inherent in hot-brewed coffee.
  
  Cold coffee drinks such as Frappuccinos are premade, presweetened and typically shelf stable. They are usually made using heat-brewed coffee.
  
  Section::::Variations by country.:Vietnam.
   BULLET::::- Brew temperature 90-95 °C
  
  BULLET::::- Standard 200 ml water
  
  BULLET::::- 4 g of tea
  
  BULLET::::- Brew times: 60-40-60-70-80-(+10) seconds
  
  A cold vessel lowers the steep temperature; to avoid this, always rinse the vessel with +90 °C (+194 °F) water before brewing.
   Section::::Further sensations and transmission.:Coolness.
  
  Some substances activate cold trigeminal receptors even when not at low temperatures. This "fresh" or "minty" sensation can be tasted in peppermint, spearmint, menthol, ethanol, and camphor. Caused by activation of the same mechanism that signals cold, TRPM8 ion channels on nerve cells, unlike the actual change in temperature described for sugar substitutes, this coolness is only a perceived phenomenon.
  
  Section::::Further sensations and transmission.:Numbness.
   A subtler issue is "which" solubles are dissolved – this depends on solubility of different substances at different temperatures, changes over the course of extraction (different substances are extracted during the first 1% of extraction than in the period from 19% extraction to 20% extraction), and is primarily affected by "temperature."
   Cold brew coffee is made by steeping coarsely ground beans in cold water for several hours, then filtering them. This results in a brew lower in acidity than most hot-brewing methods.
  
  Section::::Processing.:Nutrition.
  
  Brewed coffee from typical grounds prepared with tap water contains 40 mg caffeine per 100 gram and no essential nutrients in significant content. In espresso, however, likely due to its higher amount of suspended solids, there are significant contents of magnesium, the B vitamins, niacin and riboflavin, and 212 mg of caffeine per 100 grams of grounds.
  
  Section::::Processing.:Serving.
   BULLET::::6. Sweltering / Yellowing: Unique to yellow teas, warm and damp tea leaves from after kill-green are allowed to be lightly heated in a closed container, which causes the previously green leaves to turn yellow. The resulting leaves produce a beverage that has a distinctive yellowish-green hue due to transformations of the leaf chlorophyll. Through being sweltered for 6–8 hours at close to human body temperatures, the amino acids and polyphenols in the processed tea leaves undergo chemical changes to give this tea its distinct briskness and mellow taste.
   BULLET::::2. experience, such as prior exposure to taste-odor mixtures
  
  BULLET::::3. internal state
  
  BULLET::::4. cognitive context, such as information about brand
  
  Section::::Temperature modality.
  
  Section::::Temperature modality.:Description.
  
  Temperature modality excites or elicits a symptom through cold or hot temperature. Different mammalian species have different temperature modality.
  
  Section::::Temperature modality.:Perception.
   Temperature can be an essential element of the taste experience. Food and drink that—in a given culture—is traditionally served hot is often considered distasteful if cold, and vice versa. For example, alcoholic beverages, with a few exceptions, are usually thought best when served at room temperature or chilled to varying degrees, but soups—again, with exceptions—are usually only eaten hot. A cultural example are soft drinks. In North America it is almost always preferred cold, regardless of season.
  
  Section::::Further sensations and transmission.:Starchiness.
   Cold brewing, also called "cold water extraction" or "cold pressing," is the process of steeping coffee grounds in water at cool temperatures for an extended period. Coarse-ground beans are soaked in water for a prolonged period of time, for 12 to 24 hours.
   BULLET::::- "Glossodoris angasi"
  
  BULLET::::- "Glossodoris aureola"
  
  BULLET::::- "Glossodoris bonwanga"
  
  BULLET::::- "Glossodoris buko"
  
  BULLET::::- "Glossodoris cincta"
  
  BULLET::::- "Glossodoris erythraea"
  
  BULLET::::- "Glossodoris gregorius"
  
  BULLET::::- "Glossodoris hikuerensis"
  
  BULLET::::- "Glossodoris kahlbrocki"
  
  BULLET::::- "Glossodoris katoi"
  
  BULLET::::- "Glossodoris kophos"
  
  BULLET::::- "Glossodoris limbata"
  
  BULLET::::- "Glossodoris lamberti"
  
  BULLET::::- "Glossodoris misakinosibogae"
  
  BULLET::::- "Glossodoris moerchi"
  
  BULLET::::- "Glossodoris pallida"
  
  BULLET::::- "Glossodoris pantherina"
  
  BULLET::::- "Glossodoris prismatica"
  
  BULLET::::- "Glossodoris rufomarginata"
  
  BULLET::::- "Glossodoris semeion"
  
  BULLET::::- "Glossodoris souverbiei"
  
  BULLET::::- "Glossodoris thalassopora"
  
  BULLET::::- "Glossodoris vespa"
  
  BULLET::::- "Glossodoris xishaensis"
  
  BULLET::::- Species brought into synonymy:
  
  BULLET::::- "Glossodoris acriba": synonym of "Felimare acriba"
   BULLET::::4. Owing to the "circumstances, conditions or dispositions," the same objects appear different. The same temperature, as established by instrument, feels very different after an extended period of cold winter weather (it feels warm) than after mild weather in the autumn (it feels cold). Time appears slow when young and fast as aging proceeds. Honey tastes sweet to most but bitter to someone with jaundice. A person with influenza will feel cold and shiver even though she is hot with a fever.
   BULLET::::- Coffee tag – Each coffee sample tray will have a tag with the lot number, region, type of coffee bean and year grown listed on it, so that the taster can inspect the history of the coffee being tasted.
  
  BULLET::::- Hot water kettle and heating stand – Traditionally there is one or more large brass kettles in a heating stand nearby the coffee tasting table keeping water at the ideal temperature for coffee tasting, which is typically just below boiling temperature.
   The amount of coffee used affects both the strength and the flavor of the brew in a typical drip-brewing filtration-based coffee maker. The softer flavors come out of the coffee first and the more bitter flavors only after some time, so a large brew will tend to be both stronger and more bitter. This can be modified by stopping the filtration after a planned time and then adding hot water to the brew instead of waiting for all the water to pass through the grounds.
   Section::::Reception and legacy.
   The method of adding hot water produces a milder version of original flavor, while passing more water through the load of ground coffee will add other flavors to the espresso, which might be unpleasant for some people.
  
  Section::::Cold.
   Factors affecting the chill filtering process include the temperature, number of filters used, and speed at which the whiskey is passed through the filters. The slower the process and the more filters used, the more impurities will be collected, but at increasing cost.
   In addition to the "cold press", there is a method called "Cold Drip Coffee". Also known as "Dutch Ice Coffee" (and very popular in Japan), instead of steeping, this method very slowly drips cold water into the grounds, which then very slowly pass through a filter. Unlike the cold press (which functions similar to a French Press) which takes eight to twenty-four hours, a Cold Drip process only takes about two hours, with taste and consistency results similar to that of a cold press.
  
  Section::::Brewing.:Pressure.
   Since gyokuro is typically steeped at such a low temperature, sources may recommend preheating both the pot and cup to maintain the warmth of the tea as one drinks it.
  
  Section::::Cultivation.
  