Where Does Coffee's Sweetness Come From and What Factors Influence It? Why Can't You Taste Sweetness in Pour-Over Single-Origin Coffee

For more professional coffee knowledge exchanges and coffee bean information, please follow Coffee Workshop (WeChat public account: cafe_style)

Introduction

When purchasing coffee beans, you'll often find sweet descriptions like honey, cane sugar, and caramel in the flavor notes. But strangely, some people can taste sweetness in the same coffee beans while others cannot! What exactly causes this? Where do these pleasant sweet flavors come from?

What are Sugars?

Carbohydrates (sugars) are divided into monosaccharides, disaccharides, and polysaccharides, accounting for about 50% of the weight of raw coffee beans.

Monosaccharides are the simplest structural sugars that dissolve in water and have a sweet taste. Glucose, fructose, mannose, arabinose, and galactose all belong to monosaccharides.

Disaccharides are formed by the dehydration of two monosaccharide molecules, dissolve in water, and have a sweet taste. Sucrose, lactose, and maltose all belong to disaccharides.

Polysaccharides are composed of more than ten monosaccharide molecules, are insoluble in water and have no sweet taste, and are the main component of lignocellulose in coffee beans.

What Affects the Sweetness of Coffee Beans?

Coffee Varieties

Let's first look at the proportion of sugars in Arabica and Robusta raw beans.

From the data, we can see that the proportions of polysaccharides and monosaccharides in Arabica and Robusta coffee beans are roughly the same. The only factor affecting coffee sweetness is sucrose. The higher the sucrose content, the better the coffee flavor, which explains why Arabica coffee beans taste much better than Robusta coffee beans.

Secondly, there's the maturity of the coffee cherries. As coffee fruits ripen, the sucrose content in the pulp and mucilage also increases. Through drying, these sugars are transferred to the coffee seed (coffee bean).

Coffee Growing Altitude

The higher the growing altitude, the greater the temperature difference between day and night, and the longer the ripening time of coffee fruits. Warm sunlight during the day helps coffee fruits form sugars, while cold nights reduce the respiration of coffee plants, decreasing sugar consumption. The higher the altitude, the greater the temperature difference, giving coffee fruits more time to form more sugars. This is why coffee beans grown at higher altitudes have higher sweetness.

Coffee Bean Processing Methods

Different processing methods also affect the sweetness expression of coffee beans. Taking the washed processing method and the natural processing method as examples.

In washed processing, coffee beans have their skin and pulp removed and are then placed in water for fermentation to remove mucilage. Due to water soaking, the coffee bean embryo becomes active and begins to digest the sugars stored in the coffee beans, while also increasing the amino acid content. This is why washed-processed coffee beans have more pronounced acidity and a cleaner taste.

In natural processing, coffee beans are dried with their entire skin, pulp, and mucilage intact. During the drying process, the moisture content inside the fruit decreases, inhibiting the activity of the embryo. Meanwhile, the sugars in the pulp and mucilage are slowly absorbed by the coffee beans. This is why naturally processed coffee beans have more pronounced sweetness and a fuller body.

Coffee Bean Roasting

The caramelization reaction during coffee roasting plays a very important role. Insufficient caramelization makes coffee taste bland, while excessive caramelization makes coffee taste bitter. The caramelization reaction occurs at roasting temperatures between 170-205°C, which coincides with the temperature during the first crack stage of coffee beans.

The first crack stage occurs when sucrose in coffee beans releases water vapor and carbon dioxide after dehydration, causing the originally colorless sucrose crystals to turn brown while simultaneously forming aromatic compounds such as furan compounds. Furan compounds are the main components that constitute coffee aroma. The charming sweet and roasted aromas we smell in coffee mostly come from these substances.

Why Can't Everyone Taste Sweetness in Coffee?

After roasting, coffee beans undergo a series of Maillard reactions and caramelization reactions, leaving almost no sucrose content. Therefore, the sweetness described in coffee flavors is actually aromatic substances, not taste substances. If you really want to taste the sweetness of sucrose in coffee beans, you might have to chew on raw beans!

When FrontStreet Coffee's baristas cup a coffee bean, they judge the coffee's flavor through two types of olfaction: orthonasal olfaction and retronasal olfaction.

Orthonasal olfaction refers to directly inhaling through the nose to perceive external odors. For example, the citrus, floral, and herbal aromas we smell after grinding coffee beans into powder, or the aromatic vaporizing substances that only volatilize at high temperatures, which we often call "wet aroma," such as fruit aroma, tea aroma, sweet and sour aroma, etc.

Retronasal olfaction is often mistaken for taste from the tongue. Retronasal olfaction refers to the olfactory experience that occurs after coffee enters the mouth, is catalyzed by saliva, releasing aromatic molecules hidden in coffee oils, which then pass through the oral cavity into the nasopharynx and into the nasal cavity. For example, chocolate aroma, nut aroma, and other caramelized aromas are more pronounced in retronasal olfaction.

However, everyone's ability to identify aromatic substances varies, and not everyone can perceive the same aromas in the same coffee.

If you want to improve your ability to identify sweet aromatic substances, you can eat more foods with obvious sweet flavors, such as fruits and candies. When swallowing, close your mouth and then exhale through your nose to perform retronasal olfaction judgment, thereby enhancing your ability to recognize sweet aromas.

For more specialty coffee beans, please add FrontStreet Coffee on WeChat: ID: kaixinguoguo0925

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473