Roast defects & Development quality
Exploring phenomena such as scorching, tipping, facing, uneven roasting, underdevelopment, and baked character through physical evidence, process data, and sensory observations. The section distinguishes observable signs from hypotheses about their causes rather than diagnosing roast defects through a single metric.
Explaining the principles of mechanical separation, density separation, and magnetic separation used to reduce the risk of foreign matter in roasted coffee production. The section also clarifies the capabilities and limitations of each system across different types of foreign material.
Explaining First Crack as a marker of pressure and structural changes within the bean while examining the transformations that continue afterward. The section also clarifies the distinction between light roasting and underdevelopment without relying on a fixed temperature or Development Time threshold.
Using the multi-scale Giesen system — from 200 g and 1 kg to 6 kg and 15 kg — to explain the transition from sample roasting through development to production. Scale-up is examined as a process of recalibrating energy, airflow, machine response, and related variables rather than directly copying a curve from one roaster to another.
Explaining the role of optical sorting in identifying beans with off-color or other visual differences after roasting, while distinguishing machine vision from sample-based roast color measurements such as Agtron. Optical sorting is treated as an additional layer of physical QC rather than a replacement for sensory evaluation.
Explaining the physical changes that occur as green coffee is exposed to heat, including moisture loss, mass reduction, volume expansion, density changes, porosity development, and structural transformation within the bean. The section distinguishes physical transformation from chemical reactions while providing a foundation for understanding First Crack, roast color, gas retention, and other changes that occur throughout roasting.
Building knowledge around how a roast profile becomes a production reference through batch records, process tolerances, roast color, sensory checks, and traceability. Repeatability is understood as maintaining a controlled standard across variations in raw material, equipment, and environment rather than reproducing an identical curve every time.
Explaining the major chemical reactions and transformations that occur as green coffee is exposed to heat, including Maillard reactions, Strecker degradation, caramelization, acid transformation, volatile formation, and CO₂ generation. The focus is on interacting reaction networks rather than assigning a fixed flavor note to a single reaction or compound.
Exploring phenomena such as scorching, tipping, facing, uneven roasting, underdevelopment, and baked character through physical evidence, process data, and sensory observations. The section distinguishes observable signs from hypotheses about their causes rather than diagnosing roast defects through a single metric.
Building foundational knowledge around describing and measuring roast degree, from labels such as Light, Medium, and Dark to reflectance-based measurements such as Agtron. Roast color is treated as an important layer of information, but not as a standalone measure of development or sensory quality.
Exploring how time, temperature, Rate of Rise, Turning Point, event timing, and Development Time are used to describe roast progression. The section examines both the usefulness and limitations of these metrics rather than treating a particular curve shape or time ratio as a universal flavor formula.
Explaining how energy moves from the roaster into the coffee through conduction, convection, and radiation, alongside the influence of airflow, drum speed, batch size, and thermal mass. This section provides the foundation for understanding roast progression before introducing metrics such as RoR or First Crack.
Distinguishing the purposes of sample roasting, profile development, and production roasting while explaining how green coffee information, trial roasts, and sensory evaluation contribute to building and refining a roast profile. Sample roasting is treated as a tool for observing and comparing material rather than as a perfectly scaled-down production roast.
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