Why Can't I Taste the Sweetness in Coffee? What Is Coffee Sweetness? Should It Be Perceived by Smell or Taste?

Barista: "Hmm! This coffee has a high level of sweetness!"

You: "?? What sweet?"

Barista: "The sweetness of coffee, of course!"

You: "Coffee what???"

If you're new to single-origin coffee, you might find it confusing. Why do FrontStreet Coffee's baristas often mention that a particular coffee has excellent sweetness, yet you can't taste it at all? What is coffee sweetness? Why can't your taste buds perceive it?

Sugars in Green Coffee Beans

The sugars in green coffee beans are divided into monosaccharides, disaccharides, and polysaccharides, with sugars accounting for approximately 50% of the weight of a single green coffee bean. However! Not all sugars are sweet.

Monosaccharides are the simplest form of sugars, soluble in water and sweet in taste. Glucose, fructose, and others belong to this category. Disaccharides are formed by the dehydration of two monosaccharide molecules and are also soluble in water with a sweet taste. Sucrose, lactose, and maltose are all disaccharides.

Polysaccharides are quite special - they have no sweet taste and are insoluble in water, yet they constitute the largest proportion of coffee beans! This is because they are the main component of coffee bean cellulose (which makes up coffee grounds), formed by the polymerization of ten or more monosaccharide molecules.

Does Coffee Sweetness Come from Sugars in Green Beans?

No, it doesn't!

Coffee beans are typically roasted at temperatures above 190°C before being removed from the roaster. During this process, monosaccharides and disaccharides cannot withstand the baptism of Maillard reactions and caramelization reactions. By the time the beans are removed from the roaster, these sugar compounds that could bring sweetness to the taste buds are almost zero. What can we do if we want our taste buds to experience the sweetness from coffee beans? (Eat green beans) Of course, that's a joke!

What Actually Is Coffee Sweetness?

Do we perceive it through our taste buds or our sense of smell?

The answer is through our sense of smell. Our taste buds can only detect sour, sweet, bitter, salty, and umami flavors that are soluble in water. If these flavor compounds are not water-soluble, our tongues cannot perceive their existence, or if there are too few water-soluble flavor compounds, our taste buds find it difficult to detect a distinct taste. Although the content of monosaccharides and disaccharides is almost zero after coffee beans are roasted, it doesn't mean they're completely absent - there are still trace amounts of sweet substances infused into the coffee.

During the roasting process, FrontStreet Coffee refers to the time period between the yellowing point and the first crack as the intermediate stage. During these few minutes of the intermediate stage, the sweet and fragrant flavors of coffee are developed - this is what baristas refer to as sweetness. This sweet and fragrant flavor belongs to aroma, mostly manifesting as sugarcane, honey, or fruity sweetness; after the first crack, coffee beans gradually develop caramelized sweet flavors such as caramel, brown sugar, and black sugar. These aromas typically manifest in the aftertaste phase when tasting coffee.

The coffee aftertaste phase is perceived through our sense of smell (yes, not through taste buds). Olfaction is divided into two stages: orthonasal olfaction and retronasal olfaction. Orthonasal olfaction refers to directly inhaling air into the nasal cavity to perceive external odors. When we experience dry aroma and wet aroma, we are using orthonasal olfaction.

After entering the mouth, taste buds first detect sour, sweet, bitter, salty, and umami flavors. Then, during the swallowing process, aromatic compounds travel to the nasal cavity. At this point, our brain begins to match the flavors just tasted with the aromas that have traveled to the nasal cavity, finally presenting the flavor of a specific food. This is what we call retronasal olfaction.

How to Improve Your Ability to Identify Coffee Sweetness?

Everyone's ability to identify aromatic compounds varies. Not everyone can perceive the same aromas in the same coffee. To enhance your ability to identify sweet aromatic compounds, you can consume more foods with obvious sweet flavors, such as fruits and candies.

Before tasting, we can use orthonasal olfaction to make initial judgments and form memories. Then, when tasting and swallowing, close your mouth and exhale through your nose to perform retronasal olfactory judgment and form memories, thereby enhancing your ability to identify sweet aromas.

After training to improve your sweet taste identification, you will experience the following scenario: