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Roasting 101 – Roast Stages and the Use of Airflow

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Roasting 101 – Roast Stages and the Use of Airflow

Hi. Dave Borton – Mill City Roasters – here in Minneapolis,

continuing segments of Roasting 101.

Today we’re going to look at roast stages…

and the use of airflow.

So, where do we start?

Okay, the unit has been pre-warmed

for 40 minutes.

I’m looking…

I’ve got a drop temperature of roughly

three hundred ninety degrees

for this high-grown.

The burners are on, it’s hovering around

390.

Its been pre-warmed, I’ve got my charge loaded up…

Let’s roast.

We’ll open the hopper,

and I shut the burner off for the first minute.

I’m going to turn my air down to low.

During this drying stage,

I want all of that energy…

picking up and wicking away the moisture.

Coffee starts at about 10.5-11%

Uhm…

water moisture.

And so I want to dry that bean out

to about one half of

one percent at the end of drying.

I do that with an airflow setting of low.

Now, about five minutes or so into the roast…

I’m going to have been checking the trier

and when the beans are entirely yellow,

they’ve lost all their green hues,

I’m going to mark “end of drying” and turn my

air up to medium.

During this airflow

Uhm…

Convective energy begins to work with

conductive energy.

This is the carmelization stage: roughtly between

five minutes and first crack.

By using an airflow of medium,

so that we pick up convective

as well as conductive energy.

Long about 380 degrees on the bean

temperature, I’m going to be keeping an

eye on that bean

and when those beans

begin to have seam openings

and I begin to see the finest wisps of smoke

under that light – before first crack – I’m

going to turn my airflow up to high.

That is going to expel the smoke from

the unit and that smoke won’t cloud the

volatile oils that are in the coffee.

So from first crack, through the end of the roast

I’m going to go ahead and use an air

setting, or an air flow, of high.

That’s about as simple as it gets.

Three stages of roasting.

Drying to five minutes,

“first crack”

Before first crack, the “carmelization phase”

and “first crack” between 8 and 10 minutes

completing the third stage

which is “first crack and beyond.”

You’re going to use three airflow settings:

Low, during the -uhh – drying stage.

In the caramelization phase, I’m going to use medium.

and then 20 seconds before first crack – as indicated

by opening seams and wisps of smoke –

I’m going to use an airflow setting of high.

That’s the way we roast at Mill City Roasters.

Glad you watched in with us today

and look for other segments of

Roasting 101.

Goodbye.

WRITTEN BY:

Self proclaimed "humblest man in the universe", Nick enjoys simple things like 4th century architecture remodeling and eating unripened tomatoes.

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