Frequently Asked Questions

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Can Roastmax Roasters roast a full batch?
Why is it common for many commercial roasters to roast slightly under full capacity?
To optimise the roast & maximise the flavour, many roastmasters (regardless of the brand of roaster) prefer to roast slightly under full capacity as it gives the operator more control over the roast. This allows the beans to roast all the way through thus fully developing the flavour of the bean.
What is a gastrain?
A series of components that controls gas flow & pressure to the burners. All Roastmax Roasters have always had a gastrain & safety devices fitted in Australia to Australian standards. The roaster is ready for use once connected to gas, power & flues are installed.
Why is it important to have the right size burner to match the roaster?
A roaster with a burner that takes too long to heat the drum will end up baking the coffee resulting in a lifeless tasting coffee.

A roaster with too powerful burners heat directly onto the drum at a much faster rate than the air flowing through the roaster. As drum temperature is usually not measured, the bean temperature probe will not pick up straightaway that the drum is too hot. The beans rolling on the drum will therefore roast relatively quickly resulting in the outside of the bean being roasted while leaving the inside of the bean relatively uncooked (like searing a stake), giving little depth of flavour. Tipping is also likely to occur.

Roastmax Roasters have burners that are matched to the roaster capacity so that the air flowing through the drum rises at approximately the same rate as the drum.

Why is controlling airflow so important?
Probably the most important aspect of roasting & the least talked about is airflow. You need airflow for the following reasons:

    a) Remove the smoke.
    b) Remove the chaff.
    c) To roast the beans.
    d) Give even heat distribution to the beans.
    e) The moving air draws more oxygen to the burners providing a stronger flame.

The airflow does most of the roasting. However, unlike fluid bed roasters (air roasters), the airflow in drum roasters is much slower & gently roasts the coffee. Conductive heat from the drum contributes a smaller proportion to the roasting than airflow. When beans go exothermic, they also generate their own heat & cook themselves.

A roaster with poor airflow will result in uneven distribution of heat to the coffee beans. Roastmax Roasters take pride in producing evenly roasted coffee beans that are all one colour.

What is a regulator?
A device that reduces the pressure of the incoming gas to a set pressure. All Roastmax Roasters come with a regulator fitted to supply correct pressure to the burners. The regulator can also be adjusted minutely to fine tune the flame.
What is an injector?
A component that allows gas to pass through an orifice before it enters into the burner. It is critical that the orifice is drilled to the right size for LPG or Natural gas. Roastmax pre-drill the orifice to the correct size depending on what gas type customers are using.
Why do gas roasters produce a better coffee over electric roasters?
When gas is ignited, it expands very quickly. Heat from the burners fill every crevice in the drum & drum housing, like trying to blow up a balloon. This gives very even heat to the beans.

Electric roasters use elements to heat the roaster. The elements emit radiant heat, i.e. its hottest at the source & gets cooler as the heat moves away from the source. The beans closest to the element are subjected to higher temperatures than beans away from the element, resulting in uneven & fluctuating heat applied to the beans. For this reason, its difficult to maximise flavour from the bean to their full potential.

What is a continuous roaster?
A roaster that can roast & cool simultaneously, i.e. there is a motor dedicated for cooling. Generally these roasters have 4 motors (for drum, exhaust fan, cooling arms & cooling fan). Roastmax Roasters was first to come standard with 4 motors with speed controller on the drum.
Why is fast cooling important?
Coffee will continue to roast when released from the drum until its temperature has reduced considerably. The longer it takes to cool, the darker the coffee will become. Roastmax Roasters have powerful cooling fans to stop the roasting process very quickly.
What do the cooling arms do?
The cooling arms stir the beans so that the cooling fan cools the coffee evenly on all sides.
Do I need a flue for a roaster?
A flue or exhaust pipe is required to vent the smoke from the roaster out into the atmosphere or into an afterburner. Small roasters can sometimes use a ventilator to suck the exhaust from the building. Large roasters require an afterburner. A good well maintained flue system is crucial to the performance of your roaster. People who take shortcuts will ultimately lose customers with poor quality tasting coffee as the roaster is not performing at its optimum.
What is a datalogger?
A device that simply logs the roast temperature over time. These cost around $99 & come with a USB port so you can connect to your computer. Roastmax can supply & fit if requested.
What is a profiler?
A device that controls the temperature of the roaster in a given time automatically using a modulating burner. Normally a PID, PLC or computer is required to program & control the roast profile. Roastmax are experts in fitting profiler systems to roasters & have fitted them to a number of roasters. Our profiler systems also can control the air valve.
What is a modulating burner?
A burner that is digitally controlled via a PLC, PID or computer to automatically modulate the gasflow to the burner so that it maintains a setpoint temperature, or reaches a setpoint temperature in a certain time at a pre-determined rate.
What is a PID used for in a coffee roaster?
A device that basically mathematically calculates (using algorithms) the time & rate at which the roaster is to reach a setpoint temperature. Some PIDís have multiple steps & patterns used for profiling your roaster. Roastmax Roasters can provide profile systems with 99,000 profiles & 99 steps (stages).
What is the difference between Direct & Indirect heat roasters?
A direct heat burner has the flame directly on the drum.

An indirect heat burner has a chamber under the drum where a burner fires a flame into the chamber. The hot air rises which heats the drum & beans. Roastmax sells both direct & indirect heat models.

What is an afterburner & do I need one?
An afterburner is a separate chamber device that uses another burner to burn off the smoke from the roaster at very high temperatures so there is no visible smoke or odour. Afterburners operate at temperatures above 600 degrees. These are required on larger shop & industrial roasters or in built up areas where the smoke may affect others living or working nearby. You may need to consult the council whether you need an afterburner. Roastmax supply afterburners for roasters.
What is a destoner & do I need one?
A simple but clever suction device that separates foreign matter from the roasted coffee beans using the principle of specific gravity. A motor & fan is used to decrease the pressure in the destoner to create the suction.

Coffee beans can in fact be heavier than the foreign matter yet still be lifted up into the destoner while lighter foreign matter is left behind. Failure to remove the foreign matter can cause severe damage to coffee grinders.

Generally if you are using high grade beans, & roasting under 1000kg a week, a destoner may not be necessary. Lower grade beans however have a higher chance of containing foreign matter due to lower quality controls during the green bean grading process. Also very high volume roasters will need a destoner as the probability of coming across a foreign object gets higher as volume increases.

How does bean moisture effect the roast?
The more moisture in the bean, the longer it will take to roast. On average, during the roasting process, the bean will lose about 17%-19% moisture.
What is 1st & 2nd crack mean?
Coffee beans contain sugars which when heated caramelise. In the first stage of the roast (endothermic) the beans being porous are simply absorbing heat & expand. After several minutes, the beans will start to caramelise some of the sugars & produce their own heat (exothermic). There is a point where the beans will make a snapping noise (1st crack) as the sugars caramelise rapidly. After several more minutes, sugars trapped inside the bean begin to rapidly caramelise further producing a 2nd crack.

It is important to note that some coffees such as Greek, Turkish, filter & plunger are generally not roasted to 2nd crack.

What does endothermic & exothermic mean?
Endo = inside
Exo = outside
Thermic = heat
At the endothermic stage (early stage of roasting), heat is being absorbed into (inside) the bean. At the exothermic stage (after 1st crack), heat is being generated by the caramelising of the sugars within the bean which in turn releases the heat (outside) out of the bean & into the roaster. These terms often confuse people.