Yellow Drying Time: Not directly linked to flavor development, but indirectly affecting it because of pressure / momentum development. • Batch momentum developed • Moisture content reduced at bean surface • Internal cellular pressure developed
Maillard Reaction: Though Maillard Reactions start before yellowing and do not end at the beginning of first crack, this is the segment where they are dominant. High molecular weight compounds and complex flavoring and aromatic compounds cause significant flavor and texture development in this region.
Development Time: Time for heat to penetrate the seed after water content is removed. Closely connected with perception of fruitiness and acidity. Likely with a bell shaped curve. Also connected with the ∆ between whole bean and ground color. Faster = larger, slower = smaller. Fruitiness
< Roasting shorter in this segment reduces length of aftertaste and bitterness (as well as body) if too quick it can Potential Defects become papery and thin. • Scorching: Too much heat in the metal, beans char wherever they come in contact with the metal. Time Time Roasting longer increases length of aftertaste and • Tipping: To high of heat application (convection or conduction) and the bitterness (body & juiciness) but if taken too far becomes End temperature is symbolic of the beans char at their soft-spot (where the embryo would have emerged heavy/savory. > degree of sugar browning that the coffee has from the seed). experienced both internally and externally. This is one of the controls for whole bean and ground color.
The darker (higher temperature) you roast, the more chocolate, woody, smoky, ashy characteristics. The darker roasted coffee tends to taste more bitter. The lighter (lower temperature) you roast, the more nutty, herbaceous, floral, and fruity the coffee. Lighter roasted coffee tends to taste sweeter.
Turn Around Point During roasting, internal cellular pressure increases due to vapor pressure of water. This changes which chemical reactions can happen, as well as the rate of chemical reactions. It also increases the boiling point of water to closer to 180-200°C. As water escapes post-first crack, reactions previously suppressed can begin in earnest. < Roasting quicker to first crack reduces length of aftertaste and bitterness (as well as body) but can become papery or thin if too fast Roasting slower to first crack increases length of aftertaste and bitterness (body & juiciness) but if taken too far becomes heavy/savory>