CFRR – Most of the aroma and flavor in coffee are caused by the coffee beans roasting.
Coffee is one of the widely traded beverages in the global market. With the increasing demand for quality coffee, especially specialty coffee, the scientific sensory evaluation of coffee is rapidly interested in understanding and meeting the needs of consumers.
There are two parameters of great interest in the roasting process that is, bean color and roasting time, which affect the sensory properties of coffee beans. Color and time are related to browning rates through dark roasting, and longer times are associated with increased bitterness and decreased acidity, fruitiness, and sweetness
The varies relationship between time, temperature, and color during roasting, and affects the chemical composition depending on the degree of roasting. The color of coffee beans can help determine the degree of roasting, common roast levels such as light – medium – medium dark – dark. The longer the coffee beans are roasted, the darker the color will be, and the aroma and flavor will also change.
Popular roasting levels
Light roasts
Light roasted coffee beans usually reach a temperature of about 192-205°C, having a predominantly color is light brown, having many pleasant sour tastes close to citrus or lemon, rich aroma, more delicate taste accompanied by a thin body. Some popular light roasting levels are cinnamon, half city, light city and new england. Characterized by a stronger and more pronounced acidity, most of the sweetness will be retained in the beans because the caramelizing reaction at this stage is lower than the darker roasting levels.
For coffee beans with good physical, high quality, light roasting contributes to preserving the taste of coffee beans to get a great coffee experience. But for low-quality coffee beans, light roasting will reveal some astringent, bitter taste, and parched (dry mouth)
Medium roasts
Medium roast level is one of the popular choices with roasting temperatures around 210-220°C. Medium roasted coffee beans will have a medium brown color, medium body, and more balanced acidity, aroma, and taste. Some coffees originating from Africa will be suitable for light to medium roasting. There are common roasting levels such as american, breakfast, city, or regular. Roasting at this level will retain many of the unique flavors of coffee origin, the bright flavor notes at the light roast will be lost to give way to balance and still retain the natural aromas in the coffee.
Medium dark roasts
Coffee beans are dark brown or appear with a little oil on the surface of the roasted beans at a temperature of 225–230°C, less sour, more intense in flavor that is similar to chocolate but mellow and super smooth, faint with flavors of nuts or roasted peanuts. Roasters may also call this roast after dinner, full city, or vienna.
Dark roasts
Most people will be familiar with a darker roast because the closed flavors are as accessible as dark chocolate, cocoa, and nuts although it has a high bitterness and a full body, ending the roasting process when the temperature reaches between 240 and 250°C. Dark roasted coffee beans will be dark brown turning black, the surface of the beans is oily, and has a distinctly concentrated flavor, with a smoky smell, this type of roasting is characterized by high bitterness and low acidity. Common roast levels are espresso, french, and italian.
Coffees from Brazil and Colombia will have the best flavor notes in the medium to dark roasts because their standard flavors are chocolate and roasted nuts or caramel lingering in the aftertaste.
Photo: shutterstock pongpinun traisrisilp
Choose the right level of roasting
During the roasting process, with specific roasting stages here, the structure of the coffee beans will change from 50°C starting the transformation of protein properties and evaporation of water. Above 100°C, coffee beans will turn brown due to thermal decomposition and pyrolysis of organic compounds. At about 150°C, water vapor, carbon dioxide, and carbon monoxide are released to the outside while the particle volume increases. At 180-200°C, the breakdown of the internal structure of coffee beans during the caramelizing reaction, which is also the time when the aroma develops, aromatic compounds such as phenolic esters, carbonyl, and ester is produced that contribute to the sensory properties in coffee.
The popularity of two types of coffee that are widely consumed worldwide are arabica beans and robusta beans. Arabica coffee beans have a gentle flavor, the aroma of tropical fruits or berries, high acidity, and high sweetness. Robusta coffee beans have a higher caffeine content and a darker bitter taste. While the beans have an effect on flavor, the roasting process is the way to develop those flavors through the transformation from green beans to roasted coffee beans.
You can choose the right roasting level according to the tips below:
- If you like coffee with a bright sour taste, rich natural notes, and a long-life sweet aftertaste, choose the light roast with arabica beans.
- If you like coffee with low acidity, aroma, and balanced sweetness but less fruity flavors than chocolate or caramel, choose medium to medium-dark roast.
- For the dark roast level chosen by many users for a cup of dark coffee, the bitterness is high, and the acidity is almost the lowest, with the taste of dark chocolate or the aroma of roasted nuts. If you prefer a dark roast, you may want to consider using a combination of arabica and robusta beans in your desired ratio.
Roast level and taste sensation
All flavors, aftertaste, sweetness, acidity, and consistency in brewed coffee are created by different chemical compounds and in typical reactions such as mailard, and caramelization during roasting. The sensory evaluation of dry flavors, then wet flavors, and flavors will be analyzed at different stages in the cupping process
The compounds that make up the flavor in coffee include both volatile and non-volatile compounds, the amount of these compounds will depend on the quality of the green beans, but the chemical composition of the green beans and roasted coffee beans is different.
Non-volatile compounds that affect the taste in brewed coffee can be mentioned as caffeine and trigonelline which contribute to the bitterness and aroma of roasted coffee beans, chlorogenic acid, quinic acid, and caffeic acid increase bitterness in brewed coffee at the level of dark roast, carbohydrates and polysaccharides contribute to the retention of volatile compounds that produce aroma, consistency, sweetness in a cup of coffee, lipids contribute to the texture of brewed coffee, especially the way crema is created in espresso, and the last is melanoidin, product characteristic of mailard reaction that produces the brown and taste of roasted coffee beans.
Volatile compounds create interest in coffee beans that play a role in determining the aroma and flavor of the coffee. These volatile compounds are formed during the roasting of coffee and are also associated with the quality of green beans. After roasting, more than 800 volatile compounds can be formed, but only about 20 volatiles contribute to the characteristic aroma of a cup of coffee.
Volatile compounds include hydrocarbon, alcohol, aldehyde, ketone, carboxylic acid, phenol, furan, pyrazine, etc. From a scientific perspective, these compounds are very unfamiliar to most coffee drinkers. Fortunately, the set of 36 scents from Le Nez du Café has transformed from confusing scientific names into intimate aromas for sensory perception and enhanced sensory skills in enjoying coffee.
Among them, compounds such as ketone and aldehyde will be perceived as floral and fruity or benzaldehyde which determines the aroma of apricots. The smell of caramel or roasted coffee is the result of furan and furanone. Pyrazines contribute to the smell of nuts and roasted coffee. And the interaction of some compounds will give the odors that are noted as negative such as phenolic and burning odors.
The reactions that take place continuously during roasting are factors in changing the compounds that contribute to the flavor of coffee beans. So, in the roasting levels from light to dark, there are changes found and recorded by Jean Lenoir in a set of 36 scents in coffee.
The set of 36 scents in coffee is contained in 36 glass jars divided into 4 groups of scents as follows:
- Enzymatic: characterized by floral, fruity, and herbal aromas is a group of scents found in lightly roasted coffee beans.
- Sugar browning: a group of scents obtained when coffee beans are roasted at a medium level, beans will tend to turn to scents like caramel or chocolate.
- Dry distillation: coffee beans that are roasted for a long time at a dark roast level will turn to the smell of spices, smoke, and roasting.
- Aromatic taint: this is a group of negative scents that will appear in roasted coffee beans when errors in processing and preserving green beans occur. So, the technical errors in the roasting process, the beans will smell of straw, the smell of paper, moldy smell…
Conclusion
The sensory quality of coffee is a combination of the coffee production chain including plant genetics – collection – processing – transportation – storage – roasting – grinding – brewing. From a sensory point of view, roasting has a great influence on the quality of coffee and is also the process that can make a difference in the final coffee product.
When you enjoy coffee at different levels of roasting, you will discover and enjoy different flavor notes, thereby choosing the right roasting level for your own coffee-drinking needs.
Reference
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