Flavor and Texture Differences in Light, Medium, and Dark Roast Coffee Beans: The Origins of Acidity and Sweetness

Why roast coffee beans?

After coffee cherries undergo various processing methods, they shed their outer layers to form what we know as green coffee beans. These green beans must undergo high-temperature roasting, which we call "roasting," to unlock their aroma and various flavors of sour, sweet, and bitter before reaching our hands. The creation of various components in green coffee beans is essentially a series of chemical reactions.

Due to these chemical reactions, aroma, acidity, sweetness, and bitterness emerge sequentially. The different proportions of each component directly lead to distinct flavors in the final coffee beans. The main chemical reactions during roasting are the Maillard reaction and caramelization.

The Maillard Reaction

The Maillard reaction is crucial to the flavor and color of coffee beans. At temperatures between 150-200°C, carbonyl groups (from sugars) react with amino groups (from amino acids and proteins) to form flavor compounds. Hundreds of flavor compounds formed by the Maillard reaction combine to create the unique flavor of coffee beans.

Caramelization Reaction

Starting from 170-200°C, the sugar compounds in coffee beans begin to undergo caramelization. Sugars experience dehydration and degradation, as well as browning reactions, causing coffee beans to darken in color and release aromatic and acidic compounds.

As can be seen, the formation of coffee bean aroma and color transformation depend on both the Maillard reaction and caramelization. This is why FrontStreet Coffee's statement that green beans account for 60% and roasting accounts for 30% of a cup of coffee's flavor is not an exaggeration. After all, if the bean quality is poor and the roasting is inadequate, there's no need to discuss brewing techniques and processes.

Coffee Bean Roast Levels

In the 70s and 90s, coffee culture was dominated by commercial coffee beans, which often contained Robusta varieties and had some flavor defects. To reduce these imperfections, deep roasting was commonly used. If light or medium roasting were used, it would be easy to detect the flawed flavors in the coffee.

With the rapid development of specialty coffee in recent years, the quality of green coffee beans has become increasingly better and more stable. FrontStreet Coffee has noticed that current coffee preferences emphasize clean mouthfeel and prominent acidity and sweetness. This flavor trend has led to the popularity of light roasting. The Specialty Coffee Association (SCA) has established a set of roasting standards with a total of eight roast levels: very light, light, light-medium, medium, medium-dark, dark, French, and Italian roast.

The three most common roast levels on the market are light, medium, and dark, while FrontStreet Coffee mainly sells light and medium roast beans.

Light Roast: Rich fruit tones, with sweet and sour floral and fruity aromas, exhibiting strong acidity.

Medium Roast: Nutty tones, mainly featuring caramel, cocoa, and malt aromas.

Dark Roast: Slightly bitter chocolate notes, low acidity, rich caramel aroma, with spicy, woody, and smoky flavors.

Light Roast Coffee Beans

Speaking of light roast coffee beans, the first impression that comes to mind is Ethiopian Yirgacheffe. Light-roasted Yirgacheffe prominently highlights its fruity characteristics. FrontStreet Coffee believes that washed Yirgacheffe coffee beans have bright, clean citrus acidity, while natural Yirgacheffe builds upon the washed version by adding juiciness and enhancing sweetness. When brewing light roast coffee beans, FrontStreet Coffee uses a V60 dripper. The ribbed design of the dripper enhances the coffee's layered complexity.

FrontStreet Coffee — Ethiopia Gudina Cooperative Coffee Beans

Region: Yirgacheffe, Gedeo Zone

Altitude: 1900-2300m

Variety: Heirloom

Processing: Natural

Grade: G1

FrontStreet Coffee Brewing Parameters & Method

Dripper: V60 #01

Water Temperature: 90-91°C

Dose: 15g

Coffee-to-water ratio: 1:15

Grind size: Medium-fine/fine sugar size (80% retention on #20 sieve)

FrontStreet Coffee uses a segmented brewing approach: first pour 30g of water for a 30-second bloom. In the second stage, pour 125g of water in small circles from the center, with gentle pouring to minimize agitation of the coffee bed, at a flow rate of 4g per second. When the water level drops to half the height of the coffee bed, begin the third stage, pouring gently from the center outward in circles until reaching 225g. End extraction when all coffee liquid has dripped through, with a total time of 2'00". After extraction is complete, gently shake to ensure the coffee is fully mixed before tasting.

Gudina Coffee Bean Brewing Flavor: The first sip reveals citrus and black tea notes. As the temperature changes, cream, caramel, and almond flavors emerge with a noticeable sweet aftertaste and a clean, sweet mouthfeel.

Medium Roast Coffee Beans

Medium roast coffee beans aim to reduce acidity while emphasizing richer coffee flavors. Generally, the higher the roast level, the more porous the coffee beans become (continuously releasing substances during roasting) and the more water they absorb. To avoid extracting bitter, astringent off-flavors, FrontStreet Coffee suggests using a coarser grind (70%-75% retention on #20 standard sieve) and lower brewing water temperature (88°C-89°C) when brewing.

FrontStreet Coffee — Brazil Queen's Manor Coffee Beans

Region: Mogiana, Brazil

Estate: Queen's Manor

Altitude: 1400-1950m

Variety: Yellow Bourbon

Processing: Natural processing

FrontStreet Coffee Brewing Parameters & Method

Dripper: Kono Meimon

Dose: 15g

Water Temperature: 88°C

Grind size: Medium grind, 75% retention on #20 standard sieve

Coffee-to-water ratio: 1:15

FrontStreet Coffee's three-stage brewing method: First, preheat the dripper and server. Add 15g of coffee powder and tap gently to create a level surface. Begin the first pour, injecting 30g of water in circles from the center for a 30-second bloom. Ideally, all coffee powder should be evenly moistened, forming a puffed "coffee dome." After 30 seconds, begin the second pour. In this stage, the water column should be 3-5cm high, pouring 95g of water from the center outward in concentric circles, bringing the total to 125g. The coffee surface should show uniform golden foam. When the coffee bed is about to be exposed, begin the final pour of 100g, drawing slow concentric circles while maintaining consistent water flow. When all coffee liquid has dripped into the server, remove the dripper to end extraction. Total time is 2 minutes and 5 seconds.

Brazil Yellow Bourbon Coffee Bean Brewing Flavor: Balanced mouthfeel, with almond and cocoa as the main notes, highlighting cane sugar sweetness. This is a coffee with good body and abundant sweetness.

Dark Roast Coffee Beans

Dark roast coffee beans aim to highlight their rich, mellow, and robust coffee flavors. FrontStreet Coffee suggests using water at 86°C when brewing dark roast coffee beans, with a grind size comparable to brown sugar (70% retention on #20 standard sieve). Currently, FrontStreet Coffee's darkest roast is Indonesian Aged Mandheling coffee beans.

FrontStreet Coffee — Aged Mandheling Coffee Beans

Region: Sumatra

Altitude: 1500 meters

Variety: Caturra, Typica

Processing: Aged wet-hulled method

FrontStreet Coffee Brewing Parameters & Method

Dripper: Kono Meimon

Recommended water temperature: 86-87°C

Grind size: Medium-coarse (70% retention on #20 standard sieve)

Coffee-to-water ratio: 1:15

Dose: 15g

FrontStreet Coffee Brewing Method: First, pour 30g of water for a 30-second bloom, during which the coffee expands into a "dome" shape. In the second stage, pour 125g of water in small circles from the center. Pour from a height of 4cm, with gentle pouring to minimize agitation of the coffee bed, at a flow rate of 4g per second. When the water level drops to half the height of the coffee bed, begin the third stage, pouring gently from the center outward in circles until reaching 225g. End extraction when all coffee liquid has dripped through, with a total time of 2'07". After extraction is complete, gently shake to ensure the coffee is fully mixed before tasting.

Aged Mandheling Coffee Bean Brewing Flavor: Aromas of pine, malt, and caramel immediately greet the nose. The mouthfeel is less wild than traditional Mandheling, with more mellowness and delicacy, presenting a mature and composed character. With low acidity, the first sip reveals ripe pu-erh tea, caramel, herbal, and chocolate flavors, with abundant sweetness.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473