Hojicha and coffee both use the terms light and dark roast. That does not mean a matching roast name comes from the same temperature or time. A coffee roaster’s manual reveals other clues to the process, including overlapping time ranges and the sounds coming from the beans.
A time chart does not draw an exact boundary between roast levels
The reference times in FUJI ROYAL’s Coffee Discovery manual are about 10–13 minutes for light roast, 11–14 for medium and 12–15 for dark. Notice that the ranges overlap.
Twelve minutes, for example, falls within all three ranges. The chart therefore does not say that reaching twelve minutes guarantees a particular roast level. Even within the guidance for this one machine, elapsed time alone cannot identify the finished roast. The figures themselves make that clear.
Cracking sounds reveal changes inside the beans
Iwatani describes a first crack followed by a second crack during roasting. FUJI ROYAL explains that gas builds up inside the beans and they expand, making crackling sounds. Sound offers information about changes in the beans alongside what can be seen in their surface colour.
The clock tells you how much time has passed since heating began; the sound tells you something about what is happening to the beans. Those are different kinds of information. Reading about roasting becomes more revealing when “how long?” is joined by “what is happening at that point?”
A signal from coffee beans is not a finishing signal for tea
Hojicha uses leaves or stems, while coffee uses beans. The cracks described here are indicators of changes in coffee beans. They cannot simply be carried over as a signal to stop roasting tea.
On the tea side, a study using stems from first-flush Yabukita tea grown in Kagoshima recorded a colour shift from yellow-green towards yellow-red during roasting. Stems also expanded in samples roasted briefly at high temperatures. Alongside the account of sound revealing changes in coffee beans, this tea study offers colour and shape as clues to changes in its samples.
A temperature needs a measuring point
A preheating temperature, the temperature of a drum’s inner wall and the surface temperature of the material refer to different places or stages. Matching numbers do not establish matching conditions if different things were measured. Temperature, like time, needs context.
When a source gives a temperature, look for the machine, where the measurement was taken, and whether it refers to preheating or to roasting in progress. Leave an unresolved comparison open rather than guessing the missing information. The same habit helps when reading about tea-roasting equipment and research.
Shared roast names do not create a shared recipe
The times given here are reference values for Coffee Discovery. They are not heating instructions for another coffee machine or for hojicha. To compare tea and coffee roasting, first follow each process on its own terms: the material, the equipment and the cues used to judge the result.
Behind the words light and dark are several kinds of information: the clock, the sound, the point where temperature is measured and changes in the material. Understanding roasting means knowing what a number explains, as well as what it leaves unanswered.