The art of roasting: our secrets after 30 years in the field

In the world of coffee, every detail counts. At Café Castelo, nothing is left to chance, from roasting and sorting to quality testing. Our approach is based on a simple conviction: for coffee to be exceptional, you must understand the science behind each bean and respect it down to the last drop.

Welcome behind the scenes of our workshop, where artisanal tradition and cutting-edge technology work hand in hand.

Infrared roasting: mastering heat

Roasting is the crucial step where green coffee beans are transformed, developing their aromas and color. At Café Castelo, we use infrared micro-roasting technology. Infrared heats the bean by radiation rather than by contact with hot air or a flame. This method allows the bean to be heated from the inside out, preventing surface burning while ensuring even roasting throughout.

Result :

• perfectly developed grains
• without smoky or bitter notes
• improved preservation of sugars and essential oils responsible for the body and cream
• and impeccable consistency from batch to batch.

This precision is key to revealing the aromatic complexity of each origin and exclusive blend: high-altitude coffees, rich in organic acids, gain in sweetness and brightness; full-bodied coffees develop a deep, chocolatey roundness without bitterness.

Infrared is modernity at the service of craftsmanship: a gentler, more respectful and more consistent roasting.

Slow roasting: respecting the natural rhythm of the bean

Beyond infrared technology, we also favour slow roasting.
Each cooking process is carried out slowly at a lower temperature, allowing the grain time to fully develop its aromatic profile without thermal stress.

This gentle approach offers several major advantages:

• a The gradual caramelization of natural sugars brings roundness and length to the palate.
• improved internal homogeneity of the grain, without burning or overheating
• a improved digestibility, because acidic and volatile compounds are naturally stabilized
• and a more balanced cup, where primary, secondary and tertiary aromas coexist harmoniously.

Slow roasting is an artisanal choice: taking the time necessary to allow the bean to reveal its full richness, rather than pushing it to performance.

Filtration: purity above all

Before, during and after roasting, each coffee bean goes through several filtration stages designed to guarantee the cleanliness, consistency and safety of the final product.

Two filtrations of coffee dust (before roasting)

Before entering the roaster, the beans first pass through two separate filtration stages designed to remove any traces of coffee dust accumulated during transport and drying. This fine dust, often invisible, can affect the consistency of the roast by preventing heat from circulating evenly. By removing it completely, a homogeneous temperature profile is achieved, resulting in a stable and precise roast, without areas of over-roasting or under-roasting.

Filtration of foreign matter (after roasting)

Once the roasting is complete, the beans pass through a mechanical filtration system to remove foreign matter.This step removes any hard or abnormal elements, such as twigs, stem fragments, or even volcanic rocks, sometimes found in high-altitude coffees. It's a crucial step to protect coffee grinders and espresso machines, while guaranteeing pure coffee, free from impurities and any risk to our clients' equipment.

The optical eye (final sorting)

Finally, the coffee passes under the optical eye, an ultra-precise sorting technology that analyzes each bean individually. In milliseconds, the machine assesses the color, shape, and density of each bean. Any deviation, such as a bean that is too pale, burnt, broken, or damaged, is automatically ejected.

Why? Because a cup of coffee contains approximately 100 beans, and just 3 or 4 imperfect beans are enough to disrupt the balance. These "off-profile" beans they bring bitterness, unpleasant acidity or herbaceous notes.

Thanks to our optical inspection system, we ensure absolute homogeneity, guaranteeing consistency and aromatic purity. It's a technology that very few artisanal roasters possess, but for us, it's essential.

Humidity: the invisible heart of quality

Humidity control is one of the most critical parameters in roasting. Yet, it is often the least understood by the general public.

Before roasting: the green bean

Green coffee must contain between 9% and 12% moisture, according to the standards of the Specialty Coffee Association (SCA) and the International Coffee Organization (ICO).

This is the ideal beach to guarantee:

• a stable and uniform roasting
• optimal preservation
• and a balanced grain density.

Below 9%, the grain becomes brittle and too dry: it heats up too quickly and burns before developing its internal aromas. Above 12%, it becomes unstable: it heats up slowly, cooks unevenly, and risks fermenting.

⚠️ The critical threshold: 12.5%

Above 12.5%, green coffee is considered not to meet international standards.

Why? Because he is entering a health risk zone. Grain that is too moist promotes the development of molds and mycotoxins, including ochratoxin A, a substance regulated by Health Canada and the European Union. These microfungi develop inside the grain, invisible to the naked eye, but devastating to food quality and safety.

Coffee that is too moist can therefore be downgraded or banned from sale. At Café Castelo, every batch received is analyzed: we reject any raw material that does not meet this strict standard.

After roasting

Once roasted, coffee naturally loses moisture. The optimal level is between 1% and 3%, depending on the degree of roasting.

This residual moisture is essential for:

• preserve volatile aromas
• avoid dehydration and loss of body
• to ensure better preservation.

Coffee that is too dry becomes dull and brittle; coffee that is too moist spoils more quickly and promotes condensation in the packaging. This is why we systematically measure the moisture content before and after each roasting in our laboratory.

Our laboratory: science at the service of taste

At the heart of our factory, our quality control laboratory plays a crucial role. We conduct pre- and post-roasting tests there, including:

• humidity and density measurement
• verification of the mass loss rate
• the evaluation of aromatic development
• and the visual and olfactory analysis of the batches.

This technical data allows us to fine-tune our cooking profiles according to each origin, each season, and each harvest batch. Each variable—temperature, time, airflow—is recorded, compared, and optimized.

Tasting after each roasting: the final judgment

Even with all the technology in the world, nothing replaces taste. After each roast, our team performs a sensory tasting (cupping). We taste each roasted batch to evaluate:

• aromatic balance
• the softness, the texture
• and consistency with the expected profile.

If the slightest deviation is detected, we adjust and discard. It is this daily rigor that has built Café Castelo's reputation: a coffee that is artisanal, consistent, and of remarkable purity.

A unique testing room: coffee tested on all machines

We know that exceptional coffee should taste great regardless of the machine. That's why our testing room at the Saint-Nicolas plant houses all the major coffee makers on the market: espresso machines, automatic machines, filter coffee makers, Keurig, Nespresso, Italian, French, and more. Each batch is prepared on several types of equipment to ensure that the taste remains consistent and balanced, whether you prefer filter coffee or a strong espresso. This approach allows us to adjust our grind and roast profiles so that each coffee delivers its best results in every situation.

Café Castelo: the science of coffee, the soul of the family

Our expertise is a blend of experience, passion, and precision. Every step, from green bean to cup, is measured, tested, tasted, and validated. We believe that quality isn't claimed, it's demonstrated, bean by bean.

At Café Castelo, infrared roasting, optical inspection, laboratory testing, sensory analysis, and multiple filtrations are not extras. They are the foundations of our commitment: to offer authentic, consistent, and impeccable coffee that lives up to the trust of our customers.