What does coffee taste like? Some people think coffee is bitter, others think coffee is a combination of sour and bitter, and still others think coffee is sweet. Why do we feel so different about the flavor of coffee?
        Because the way the cherries and green coffee are processed can affect the flavor of the coffee
        After the coffee fruit is ripe, after manual picking, sun drying or water washing to remove the outer pulp and pectin, the green coffee beans (green beans) are obtained.
        Different processing methods of coffee cherries, including sun drying, water washing, and semi-water washing, honey processing, animal fermentation, wine barrel fermentation and other methods gradually developed by modern technology, determine the quality of green beans. different flavors.
        Green coffee beans are mainly composed of natural chemicals such as water, carbohydrates, proteins, esters, alkaloids, chlorogenic acid, citric acid, malic acid, quinic acid, and phosphoric acid. After hot roasting, these chemicals undergo a series of chemical reactions after high temperature baptism. Different roasting methods change the proportion of various components in the beans, and the different flavors of coffee are stimulated. Come on, let's take a look at the chemicals and their changes that make coffee so attractive.
        The bitter taste of coffee comes from three aspects.
        Caffeine (scientific name 1,3,7-trimethylxanthine) is a xanthine alkaloid compound with a bitter taste. It has the effect of stimulating gastrointestinal motility and promoting defecation. It is also the most widely used psychoactive drug in the world and is addictive. It deprives you of sleep and can cause problems for people with general anxiety. Caffeine and/or its metabolites accumulate in large quantities throughout the enterohepatic circulation, and excessive caffeine exposure may increase the risk of fatty liver disease. There are also studies that suggest caffeine is a common cause of atrial fibrillation.
         Maillard reaction is a complex non-enzymatic browning reaction between reducing sugar and amino acid during food processing, that is, the process of combining sugar and protein (amino acid) to form melanin, which promotes the unique flavor and attractiveness of food. The formation of color, such as the wheat aroma and golden yellow substance produced by bread baking, the meat aroma of fried steak, etc. However, during the heat treatment, the Maillard reaction will cause the loss of amino acids, reduce the nutritional value of food, and even produce toxic substances, which has been one of the hot spots of scientific research at home and abroad for many years. With the increase of the roasting degree of green beans and the degree of coffee extraction, the by-products of Maillard reaction of protein, chlorogenic acid and other substances in coffee will also increase, and the coffee flavor will become more complex.
        The bitterness of coffee is also affected by the water temperature, time and particle size of the coffee powder. During extraction, the higher the water temperature, the longer the time, and the smaller the particle size, the more bitter substances are dissolved and the taste is more bitter; on the contrary, the lower the extraction temperature, the shorter the time, and the larger the particle size, the more sour substances are dissolved. For example, coffee extracted with water at 100°C in a moka pot has a higher content of the final product of Maillard reaction than coffee extracted with espresso machine at 88°C, and the taste is more bitter.
        The sour taste of coffee comes from natural chemicals such as quinic acid, citric acid, malic acid, and phosphoric acid, as well as new sour substances generated during the roasting process, such as the decomposition of chlorogenic acid to form quinic acid, and the decomposition of sugars to form volatile formic acid and acetic acid.
        The intensity of the sour taste of coffee is related to the degree of roasting of the coffee beans. During the roasting process of beans, before the Maillard reaction occurs, with the deepening of the roasting degree, the acidity becomes heavier.
        The intensity of the sour taste of coffee is also related to the origin of the coffee beans. Coffee trees at higher altitudes grow more slowly, and coffee beans contain higher acidity and sugar.
        The aroma of coffee comes from more than 200 kinds of volatile aromatic substances, amino acids, etc. in coffee beans. The difference in composition and content of these substances and the changes in the roasting process of green beans form various aromas of coffee.
        What are the production links that affect the flavor of coffee?
1. Baking method
        The roasting degree of green beans is divided into light, medium and dark, different roasting degree, different coffee flavor. Light roasted coffee beans have a shorter roast time and usually have higher acidity. Medium-roasted coffee beans are slightly sweeter than light-roasted coffee, with a balance of sweetness and acidity. Dark roasted coffee beans, usually stronger in flavor and more bitter in taste.
2. Brewing temperature
        Temperature affects the dissolution of natural substances in coffee grounds. The natural substances in coffee powder, including sour, sweet and bitter substances, are extracted into the solution (coffee liquid) at different speeds. Sour substances are various acids with simple molecular structure, small mass, and the fastest extraction speed; followed by sugar; the slowest extraction is the bitter substance. The higher the temperature, the faster the extraction speed of various substances. At this time, the bitter substances with slow extraction speed will dissolve more than when the temperature is low.
        Temperature affects the richness of coffee flavors. In hot coffee, volatile aromatic substances are more active and produce a strong aroma, which is why many people fall in love with coffee. After the coffee is cooled, the flavor will deteriorate. If milk or sugar is added, it is easier for bacteria to grow. Therefore, it is recommended to brew the coffee and drink it immediately, and the specialty coffee should be consumed within 5-20 minutes.
        Temperature also affects our taste perception. At different temperatures, our sensitivity to sour, bitter, and sweet tastes is different. Low temperature makes our perception of bitterness and sweetness decrease, and perception of sourness is more sensitive. Therefore, we can better experience the delicate aroma of hot coffee, and taste the sweetness of coffee without adding sugar, while hand-brewed coffee will feel more sour if it is stored for a long time at room temperature or in a cold air-conditioned environment. People who like sweets drink coffee, it is recommended to choose hot drinks.
3. Holding time
        The amount of natural substances in the coffee grounds extracted into the solution (coffee liquor) is affected by the temperature and standing time of the coffee liquor. The lower the temperature of the coffee liquid, the longer the low temperature state, the more sour substances are dissolved; the higher the temperature of the coffee liquid, the longer the high temperature state is, the more bitter substances are dissolved.
        The length of the coffee beans also affects the coffee flavor, which decreases with the prolongation of the coffee beans. The beans that have just been roasted slowly release carbon dioxide during the placement process, volatile substances are also taken away, and the pleasant aroma gradually disappears. At this time, you can experience the deterioration of the coffee.
        However, no matter how fragrant and tempting coffee is, don't be greedy! The coffee industry defaults to a cup of espresso liquid prepared from 18g of coffee powder, which contains an average of 60-80mg of caffeine. The safe daily intake of caffeine is 400mg. Considering the Maillard products produced by dark roasted coffee beans and the habit of drinking coffee everywhere, most studies recommend that coffee intake per person should not exceed 1-3 cups per day.