Coffee Roasting Temperature and Coffee Profiles

Roasting Temperature and Heat Transfer

The article examines the relationship between the roaster’s operating temperature and the temperature of the coffee beans. It recommends an operating range of 140–165°C, or roughly 300°F.

Bean temperature continues to rise over time even when the machine remains at a constant setting. Heat moves from the exterior of each bean toward its center, with the fastest temperature change occurring after the drying phase.

During drying, water inside the green coffee turns to vapor. This contributes to heat transfer through both direct contact and convection. The article notes that the bean’s temperature can be measured as it exits the roasting machine.

Bean Density and Chemical Composition

Bean density influences resistance to heat and the rate at which internal chemical changes develop. The article gives a typical green-coffee density range of 0.64–0.72 g/mL and identifies values above 0.68 g/mL as high density.

It associates density with the concentration of chlorogenic acids, a family of polyphenol esters that includes compounds formed from caffeic, ferulic, or p-coumaric acids combined with quinic acid. Green coffee is described as containing approximately 6–7% chlorogenic acids by mass.

The concentration of aroma- and flavor-related compounds can be affected by several factors:

• Bean density
• Coffee variety
• Soil composition and nutrients
• Rainfall and irrigation
• Sunlight and other growing conditions
• Altitude
• Fermentation and processing method

Honey and natural processing can introduce additional aromas and flavors.

Altitude and Bean Development

The article links higher farm altitude with lower atmospheric oxygen and greater physiological stress on coffee plants. Alongside variety, latitude, water, sunlight, and soil nutrition, altitude may contribute to denser beans and a higher concentration of desirable compounds.

Altitude-based classifications vary by country and latitude. The abbreviations discussed are:

• SHB: Strictly Hard Bean
• SHG: Strictly High Grown or Strictly High Grade
• HG: High Grown or High Grade

As an example, the article states that Costa Rica commonly classifies coffee grown above about 1,200 meters as SHB, while a comparable threshold in northern Nicaragua may be around 1,000 meters.

The Maillard Reaction and Roast Curves

The Maillard reaction occurs when amino acids and sugars react in the presence of heat. It contributes to the development of roasted coffee’s color, aroma, and flavor.

A roasting curve plots bean temperature against time. A complete profile can also show the cooling stage that follows roasting. The behavior of the curve depends on the heat source, the roaster’s heat distribution, and the properties of the green coffee.

Moisture and Density in Profile Design

The article identifies two principal green-coffee variables that affect bean temperature during roasting:

1. Moisture: Green coffee should contain approximately 10–12% moisture, with consistent moisture across the entire batch. The article gives a typical roasted output yield of about 80–83% of the input weight.
2. Density: Dense, well-sorted beans generally resist heat more effectively and may develop more evenly.

Roasters should adapt heat application to the coffee rather than relying on temperature alone. Moisture consistency, density, batch size, airflow, heat distribution, and elapsed time all influence the resulting profile.

Roasting Samples

A roasting sample is a representative portion of green coffee used to assess quality and roasting behavior. The article describes sample batches of approximately 250–300 grams and recommends retaining part of a larger supplied sample as a reference.

For general evaluation, coffee is often roasted to a light City profile so that subtle flavors remain perceptible. The article places this around 75–85 on the Agtron color scale. Longer medium or dark roasts may reduce some delicate characteristics while intensifying caramelized, chocolate-like flavors and lowering perceived acidity.

Customized sample roasting can test how a coffee responds to a target profile. One example is a Full City roast around 55–65 on the Agtron scale, evaluated for changes in aroma, body, flavor, and overall balance. Such trials support quality control and help roasting businesses match a profile to the characteristics of a particular coffee.