Wine tasting is the sensory examination and evaluation of wine. Wines contain many chemical compounds similar or identical to those in fruits, vegetables, and spices. The sweetness of wine is determined by the amount of residual sugar in the wine after fermentation, relative to the acidity present in the wine. Dry wine, for example, has only a small amount of residual sugar. Some wine labels suggest opening the bottle and letting the wine "breathe" for a couple of hours before serving, while others recommend drinking it immediately. Decanting (the act of pouring a wine into a special container just for breathing) is a controversial subject among wine enthusiasts. In addition to aeration, decanting with a filter allows the removal of bitter sediments that may have formed in the wine. Sediment is more common in older bottles, but aeration may benefit younger wines.
Although red wine contains the chemical resveratrol and there is tentative evidence it may improve heart health, the evidence is unclear for those at high risk as of 2013. Grape skins naturally produce resveratrol in response to fungal infection, including exposure to yeast during fermentation. White wine generally contains lower levels of the chemical as it has minimal contact with grape skins during this process.
Some foods not from animal or plant sources include various edible fungi, especially mushrooms. Fungi and ambient bacteria are used in the preparation of fermented and pickled foods like leavened bread, alcoholic drinks, cheese, pickles, kombucha, and yogurt. Another example is blue-green algae such as Spirulina. Inorganic substances such as salt, baking soda and cream of tartar are used to preserve or chemically alter an ingredient.