Usually when we buy coffee beans, if we want a sweeter taste, we will give preference to sun-treated coffee over washing. Is sun-dried coffee really sweeter than washed coffee? Where does the sweetness come from?
As mentioned in previous articles on Front Street, the sweetness in coffee we drink mainly comes from the amount of carbohydrates (sugars) in green beans, and the higher the sucrose content, the better the sweetness. The sucrose content depends on growth factors such as the variety of coffee, the ripeness of the berries, and the altitude at which it is grown, and is not affected by the way the green beans are handled.
In 1963, Michael Sivetz, a well-known coffee chemist in the United States, wrote "Coffee Processing Technology" (Coffee Processing Technology) and in 1994, food chemist Alan Varnam's research pointed out that the composition derived from the sun-dried method is significantly different from the washing method, and the fat, sugars and acids contained in sun-dried beans are higher than those of washed beans.
The structure of a coffee cherry can be divided into peel, pulp, pectin, sheepskin, silver skin, and seeds.
When washing, the skin and flesh need to be peeled and fleshed by a machine before drying, and the remaining inner seeds and a layer of sticky pectin are thrown into the sink to allow the acidic substances produced by fermentation to decompose the pectin. The coffee bean is soaked in water, so that the bean mistakenly thinks that it has come to a suitable environment for growth, so it begins to want to sprout, so it causes some chemical changes in the bean and consumes the simple sugars (fructose and glucose) in the coffee, resulting in a decrease in the sugar content of the green coffee bean, and at the same time increases a part of the amino acids. Amino acids are the precursors for the complex aroma of coffee.
The plant hormones and water in the pulp inhibit the germination of the seeds, and the metabolism of the new city in the green beans will be completely stopped, and the sugar content will of course be more than that of washed coffee.
Compared with washing, the fermentation time of the sun treatment is longer, and the reaction between the bacteria and the pulp is higher. When the fruit begins to ferment, the microorganisms produce more volatile compounds, especially esters. While most of the sugars are destroyed during baking, these compounds are converted into another form of aromatic compound during the caramelization reaction. It is also these aromatic substances that provide more floral aromas and fermented aromas of tropical fruits, such as esters, that give coffee a wider range of flavors and a sweeter taste.
Although the sun-dried method can preserve more monosaccharides, it does not mean that sun-dried beans are necessarily sweeter than washed beans. Coffee beans are dehydrated and dried when the sugar content is at its highest, and if the fruit is over-fermented and produces spoilage acid, or if the fermentation process is not properly controlled, resulting in mold, it is easy to release undesirable sourness or bitterness after brewing, which affects the sweetness performance of the final coffee.
In addition to the processing method, the difference between roasting and extraction can also affect the sweetness of the coffee.
Roasting sublimates the sugary content of the coffee, and the professional roaster knows how to achieve the highest sweetness point and how much acidity is retained in the coffee, so that the sweet, sour and bitter aromas of the coffee interact and ultimately affect the overall impression when we taste it. Therefore, with a reasonable roasting certainty, we may still be able to drink washed coffee with a stronger sweetness than sun-dried coffee.
A coffee bean that has reached its sweet point in roasting will also affect the final taste performance due to the difference in brewing parameters. Sour will neutralize sweetness, bitterness will suppress sweetness, and coffee that is too sour or too bitter will affect the feeling of sweetness in the mouth.
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