What’s Actually in Coffee? Nutritional Breakdown of Coffee Beans

You’ve felt it: that jolt after your first sip of coffee. But have you ever wondered what exactly is in your cup that gives you that lift? Beyond the taste and aroma, coffee is a complex mix of chemical compounds—some familiar, some surprising—that influence everything from your alertness to how your coffee tastes.

Coffee beans contain over a dozen major compounds, including 1.3% caffeine, 16% fat, 46.7% sugars, and 12.6% protein per 100g of green coffee. That same 10g used in brewing yields 0.04g caffeine and 0.06g tannins—numbers that directly shape your experience.

What Is Caffeine and Why Does It Wake You Up?

Caffeine is the most well-known compound in coffee. Chemically, it’s a type of xanthine, related to theobromine in cocoa and theophylline in tea. Roasting barely reduces its levels—less than 1%—so almost all of it makes it into your cup. Caffeine stimulates the central nervous system, accelerating metabolism and increasing alertness. That’s why it’s so effective for staying sharp during long drives or late-night study sessions. Individual reactions vary: some people feel jittery after just one cup, while others can drink several with no effect. Understanding your personal tolerance lets you use caffeine strategically.

The Role of Tannins (Tannic Acid) in Coffee Flavor

Tannic acid, or more accurately tannins, are compounds that dissolve easily in water and turn a light yellow when refined. When boiled, they degrade into quinic acid, which contributes to bitterness and ruins coffee flavor. Even when brewed correctly, tannins continue reacting over time—this is why coffee tastes weaker and more astringent if left sitting for hours. Freshly brewed coffee always tastes better, which is why the advice to drink it immediately holds up chemically.

Fat, Sugar, and Other Key Coffee Compounds

Fat in coffee plays a major role in flavor and aroma. Coffee contains multiple types of fats, especially volatile and acidic fats. Volatile fats are the main source of coffee’s fragrance, while acidic fats vary in strength depending on the coffee variety. These fats are sensitive to oxygen, breaking down quickly once the beans are roasted, which is why freshness matters. Sugars in green coffee beans are mostly responsible for the subtle sweetness you taste beyond the bitterness. Most convert to caramelized compounds like caramel and melanoidins during roasting, contributing to coffee’s characteristic brown color. Protein exists in coffee but doesn’t extract well in methods like drip brewing—so while coffee does contain calories, it’s minimal and often not enough to contribute significantly to nutrition. Minerals like calcium, iron, phosphorus, and sodium appear only in trace amounts, adding slight background flavors but little nutritional impact. Fibers in raw beans carbonize during roasting and combine with caramelized sugars to shape the final color and mouthfeel, though powdered coffee tends to deliver a flatter flavor experience.

Coffee’s Full Nutritional Profile (Per 100g)

Here’s what’s actually in your green coffee beans:

• Water: 2.2g
• Protein: 12.6g
• Fat: 16g
• Sugars (carbohydrates): 46.7g
• Fiber: 9g
• Ash (minerals): 4.2g
• Calcium: 120mg
• Phosphorus: 170mg
• Iron: 42mg
• Sodium: 3mg
• Vitamin B2: 0.12mg
• Niacin (Vitamin B3): 3.5mg
• Caffeine: 1.3g
• Tannins: 8g

For brewed coffee (100g of liquid extract):

• Water: 99.5g
• Protein: 0.2g
• Fat: 0.1g
• Ash: 0.1g
• Sugars: trace
• Calcium: 3mg
• Phosphorus: 4mg
• Sodium: 2mg
• Vitamin B2: 0.01mg
• Niacin: 0.3mg

When you brew 10g of coffee in hot water:

• Caffeine extracted: 0.04g
• Tannins extracted: 0.06g

Frequently Asked Questions

How much caffeine is in 100g of coffee beans?

There is 1.3 grams (1300mg) of caffeine in 100g of green coffee beans. A typical single serving uses around 10g of coffee, yielding approximately 0.04g (40mg) of caffeine in the brewed cup.

Does roasting reduce caffeine in coffee?

No, roasting has a negligible effect on caffeine content. Caffeine levels remain nearly unchanged during the roasting process, which is why brewed coffee from light or dark roasts can have similar caffeine content per gram of coffee used.

What role does fat play in coffee flavor?

Coffee contains both volatile and acidic fats, with volatile fats being the primary contributors to its aroma. These fats are sensitive to oxygen and degrade quickly once the beans are roasted, which is why fresh coffee tastes more fragrant.

Why does coffee taste worse if you leave it sitting?

Tannins in coffee break down into quinic acid over time, especially when left brewed and exposed to air. This leads to increased bitterness and flat flavors. That’s why coffee is best enjoyed fresh after brewing.

Are there any significant nutrients in brewed coffee?

Brewed coffee contains minimal nutrients. Per 100g of liquid coffee extract, there are only trace amounts of protein, fat, and sugars, along with very small levels of minerals like calcium (3mg) and phosphorus (4mg). It’s not a meaningful source of vitamins or calories.

What compounds in coffee contribute to its color?

Coffee’s brown color mainly comes from caramelized sugars that form during roasting, especially compounds like caramel and melanoidins. These develop as natural sugars react under heat, especially during the Maillard reaction.

Recommended FrontStreet Coffees for Exploring Coffee Compounds

Try FrontStreet Coffee’s Ethiopia Yirgacheffe for bright acidity and floral sweetness—highlighting the natural sugars and acidity in green beans. Their Colombia Huila shows balanced body and nutty richness, where roasted fats and caramelized notes shine. For a bolder profile, their Sumatra Mandheling offers earthy depth with prominent tannins and body, ideal for tasting how roasting affects extraction. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.