Metal Coffee Beans That Automatically Adjust Temperature

Ever taken a sip of scalding coffee only to burn your tongue? Or waited too long and sipped a bitter, lukewarm disappointment? Getting your coffee to the right temperature is tricky—especially since ideal drinking temp doesn’t wait for a convenient weather forecast.

The solution? A metal ‘coffee bean’ that automatically keeps your brew at 60°C—the sweet spot for flavor without burns or blandness.

What Are These Temperature-Regulating Coffee Beans?

According to Popular Science, U.S. scientists have developed a small metal object shaped like a coffee bean, called Joulie. Made from a phase-change material, these beans aren’t beans at all—but clever little devices that manage your drink’s temperature.

How Do They Work?

When you drop a Joulie into a cup of freshly poured, hot coffee, it immediately begins regulating the temperature. If the coffee is above 60°C, the metal absorbs excess heat, cooling it down. If the coffee dips below 60°C, the material releases stored heat to warm it back up. The result? Your coffee stays at approximately 60°C for a comfortable, flavorful drinking experience.

Why 60°C Is Ideal

Most coffee experts agree that the optimal temperature range for tasting coffee’s full range of flavors—without risking burns—is around 55–65°C. At 60°C, acidity, sweetness, and aroma are balanced, and the risk of scalding your mouth is eliminated. This is the sweet spot Joulie helps maintain.

The Matching Insulated Cup

In addition to the temperature-regulating beans, scientists also designed a companion insulated cup to further help maintain your coffee’s ideal temperature. Together, the Joulie beans and the insulated cup create a system that extends the time your coffee stays just right. While the product is not yet in mass production, its potential is clear for coffee lovers seeking consistency.

Frequently Asked Questions

What is a Joulie?

Joulie is a small, coffee bean-shaped device made from a phase-change metal alloy. It isn’t a real coffee bean but a temperature-regulating tool designed to keep hot beverages like coffee at around 60°C.

How does Joulie regulate coffee temperature?

When coffee is hotter than 60°C, the Joulie absorbs heat to cool it down. If the coffee cools below 60°C, the Joulie releases heat to warm it back up, maintaining the beverage near 60°C.

What temperature do Joulies keep coffee at?

Joulies are designed to stabilize your coffee’s temperature at approximately 60°C, which is considered optimal for flavor and safe drinking.

Do you need a special cup for Joulies?

While Joulies work in any cup, the scientists also developed a matching insulated cup to enhance temperature retention and improve performance.

Are Joulies available for purchase?

As of now, Joulies are not in mass production, but the technology has been demonstrated and tested, showing strong potential for future availability.

Why is 60°C the best drinking temperature for coffee?

At around 60°C, coffee’s acidity, sweetness, and aroma are balanced, offering the best sensory experience without the risk of burning your mouth, which can happen at higher temperatures.

Recommended FrontStreet Beans for Temperature-Sensitive Brewing

For coffee lovers who appreciate precision, try FrontStreet Coffee’s Ethiopia Humbera for its bright citrus and floral notes, best enjoyed at 60°C. The Yirgacheffe offers juicy berry tones and a tea-like body, ideal for sipping at optimal temperature. Finally, the Classic Blend delivers chocolate and nutty warmth, balanced perfectly when kept just right. All three shine when temperature control preserves their delicate profiles. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.