Ethyl acetate is an aromatic compound produced by yeast in beverage brewing, bestowing sweet fruity scents and complex flavor profiles. It's also found in food like bananas, and used to decaffeinate coffee.
Ethyl acetate is a colorless, flammable liquid with a distinct sweet odor. It's used in glue, nail polish removers and decaffeination of tea and coffee. As a byproduct of yeast fermentation it's a prominent ester in brewing.
Esters are organic compounds created when alcohols react with acids. They're responsible for many natural aromas such as ripe strawberries, jasmine and other fragrant fruits and flowers.
During fermentation, yeast converts sugars into alcohol and CO2, but also brings in a range of aromatic compounds. These elevate simple beverages into flavorful brews for a full sensory experience.
Formation of ethyl acetate by yeast occurs through a biochemical process using alcohol acetyltransferases (AATs). The enzymes catalyze a reaction between molecule acetyl-CoA and ethanol, the alcohol of fermentation.
The result is ethyl acetate and free CoA, a vital component of many cellular processes. Ethyl acetate is the most abundant ester found in beer and wine.
It directly influences flavor and fragrance profiles. In small concentrations ethyl acetate contributes desirable fruity notes like banana, pear or pineapple.
High concentrations of ethyl acetate can taste like solvent. Both ethanol and acetic acid have strong solvent properties, and levels above 100 mg/L make a harsh undesirable beverage.
The amount of ethyl acetate produced is influenced by factors including yeast strain, temperature and nutrient availability. Brewers and winemakers manage these factors for desired balance of flavors and aromas.
For example, using a high-activity yeast strain at warm temperatures can raise ethyl acetate levels by up to 50%. This dramatically affects the final aroma and flavor.
Brewers and winemakers monitor these conditions carefully to achieve a precisely balanced level of ethyl acetate. Control of these variables can create complex and enjoyable beverages.
Beyond the Booze
Ethyl acetate is a naturally occurring compound present in many fruits and as a byproduct of fermentation. Its solvent ability is used to decaffeinate coffee.
In this process, ethyl acetate bonds with caffeine, removing it while attempting to maintain much of the coffee's original flavor. In the decaffeination process, green or raw coffee beans are often treated with ethyl acetate.
This solvent selectively binds to caffeine molecules, facilitating their extraction from beans. The beans are rinsed and the remaining ethyl acetate evaporates, leaving a decaffeinated product.
This method is often referred to as the "natural decaf" process, due to the naturally occurring source of the solvent. The ethyl acetate is synthetic, not fermentation-derived, though structure of the molecule is the same.
Ethyl Acetate in Fruits
Ethyl acetate is abundant in many fruits. Bananas are the most notable example, as this compound is responsible for their signature smell. As fruits ripen, their sugar content increases.
Sugar loving yeast then gets to work. It breaks down glucose and fructose to generate ethanol, CO2 and compounds like ethyl acetate.
In the laboratory, ethyl acetate is produced through direct esterification of ethyl alcohol and acetic acid. This process involves combining acetic acid with an excess of ethyl alcohol and adding a small amount of sulfuric acid.
Ethyl acetate is an asphyxiant for insect collecting. It is also used in paints as an activator or hardener. It's applied in confectionery and perfumes. In perfume it evaporates quickly, to leave the scent on the skin.
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