Why Bulgarian Roasters Are Measuring Color, Not Just Temperature

A roaster in Sofia adjusts the gas, watches the temperature curve climb toward first crack, and pulls the batch at exactly the same point as yesterday. The beans look right. The numbers match. But the cup tastes different.

This scenario plays out in roasteries across Bulgaria every week. The problem isn't skill. Temperature, the metric most roasters rely on, tells only part of the story.

The Probe Problem

Temperature sensors inside a roasting drum measure a combination of bean temperature and ambient air temperature. As Perfect Daily Grind reports, the position, thickness, and sensitivity of these probes vary between machines. A roaster who develops a perfect profile on a sample roaster will find that same profile produces different results on a production machine.

This becomes critical as Bulgarian specialty roasters scale up. Sofia's coffee scene has grown rapidly, with over 60 specialty cafes now operating in the city. Roasters supplying these cafes face pressure to deliver consistent quality across larger batches. Temperature curves that worked at small scale break down when equipment changes.

Color, by contrast, is inherent to the bean itself. It reflects actual chemical development, unaffected by machine type or sensor placement.

What Color Actually Measures

The shift from green to brown during roasting isn't cosmetic. Two primary reactions drive the transformation: the Maillard reaction (a reaction between amino acids and reducing sugars that creates hundreds of aromatic compounds) and caramelization (the thermal decomposition of sugars). These reactions generate the flavor compounds that define a coffee's character.

Here's where it gets complicated: beans with different compositions develop color at different rates under identical temperature curves. A high-altitude Ethiopian and a low-altitude Brazilian, roasted with the same time and temperature profile, will reach different color values. Altitude, variety, processing method, and fermentation level all influence how quickly color develops.

This is why experienced roasters have always watched their beans, not just their thermometers. The difference now is that watching can be measured.

From Guesswork to Shared Language

The Agtron scale has long served as the industry standard for roast color measurement. Higher numbers indicate lighter roasts; lower numbers indicate darker. But historically, the equipment cost thousands of euros, putting it out of reach for small roasteries.

That's changing. Compact spectrophotometers have dropped in price and grown in capability. Modern devices measure both whole bean and ground coffee, display distribution graphs showing batch uniformity, and track color change in real time during roasting.

For Bulgarian roasters, this accessibility arrives at the right moment. Roasteries like Aroma Coffee, which operates three locations in Sofia and roasts from green beans under owner Georgi Gagov's SCA Roastery Diploma credentials, face exactly the challenge color analysis solves: maintaining consistency across batches and locations.

When roasters across a city use the same measurement standard, "medium roast" stops meaning different things to different people. Cafes can specify what they want. Consumers can understand what they're buying.

Real-Time Tracking Changes the Game

The most significant development isn't measuring color after roasting. It's tracking color change during the roast itself.

Фото: Виктор Младенов

Devices like DiFluid's OmniFlux can point at a roaster's observation window and generate a color curve alongside the traditional temperature curve. When a roaster sees color developing faster than expected, they can adjust energy input immediately rather than discovering the problem after the batch is finished.

One example illustrates the disconnect between temperature and color: a roaster experimenting with kombucha-soaked beans found that after 14 minutes at only 180°C (well below first crack), the Agtron reading had already dropped to 60, a medium-dark profile. The color had developed far ahead of what temperature suggested.

The Investment Question

Good color analysis equipment remains an investment. Entry-level spectrophotometers start around €200-300, while professional-grade analyzers run significantly higher. For a small roastery on thin margins, this isn't trivial.

But the cost of inconsistency is higher. A batch that misses the mark wastes green coffee, time, and customer trust. As Bulgarian roasters compete regionally with neighbors in Greece, Serbia, and Turkey, precision becomes a competitive advantage.

The roasters investing in color analysis now aren't just buying equipment. They're building the foundation for Sofia's reputation as a serious specialty coffee hub. The numbers on the screen don't replace judgment. They sharpen it.

Frequently Asked Questions

Q: What is the Agtron scale and how do roasters use it?

A: The Agtron scale is a standardized measurement system for coffee roast color, where higher numbers indicate lighter roasts and lower numbers indicate darker roasts. Roasters use Agtron readings to ensure batch-to-batch consistency and communicate roast profiles precisely with cafes and other professionals.

Q: Why doesn't temperature alone guarantee consistent roast results?

A: Temperature probes measure a combination of bean temperature and ambient air temperature, and their readings vary based on probe position, thickness, and machine design. The same temperature profile on two different roasters rarely produces identical results because the sensors aren't measuring the same thing.

Q: How much do color analysis tools cost for small roasteries?

A: Entry-level spectrophotometers suitable for small roasteries start around €200-300, while professional-grade analyzers with real-time tracking capabilities cost significantly more. Prices have dropped considerably in recent years, making the technology accessible beyond large commercial operations.