Before specialty roasters offer a new coffee to customers, they first need to perform a series of checks to reveal any defects and ensure it meets quality standards. Sample roasting is a quick and cost-effective way of performing the appropriate checks. In its most simple form, it involves roasting a small quantity of green beans, typically between 50g and 250g.

In sample roasting, the roast level tends to be light and nautral as darker roasts may mask any defect or issues in the green beans. The sample roaster’s skill is important here as the beans need to be roasted just at the right level to reveal all of their intrinsic characteristics, both positive and negative.

The roast level should not accentuate or obscure any of its qualities. At the same time, the roaster also needs to ensure that any defect in flavors is not contributed by the roast itself.

Double drum (applies only to classic drum roasters) and powerful burner:

The foundation of a good classic drum roaster is its burner and drum. As noted previously, burner output determines a machine’s true capacity.

Double drums allow for faster and hotter roasting with less risk of tipping or scorching.

Make drum quality and burner output your first two concerns when choosing a coffee bean mixer from Coffee Pro Direct.

You can easily replace or upgrade fans, valves, ducts, etc, but you cannot easily replace a drum, and upgrading a burner can be expensive. 

Variable-speed-drive (VSD) fan: 

As long as your roaster’s fan provides a reasonable amount of draw, you don’t need a variable-speed fan to produce good roasts.

But without a VSD fan, it’s impossible to maintain consistent airflow levels day to day. The combination of a digital air-pressure manometer and a VSD fan is essential for expert-level roast repeatability. 

Air manometer (aka drum-pressure manometer): 

A manometer in the duct between the roasting drum and exhaust fan is a relatively new, worthwhile addition to a roaster.

The manometer reads pressure, not flow, but that pressure reading correlates with airflow.

Using the same fan setting every day does not ensure consistent roasting because airflow may vary day to day with the weather and other factors.

Having an air-pressure manometer helps one know how to adjust the fan to provide consistent airflow every batch. (Note: directly measuring airflow requires installing probes in the exhaust duct, but the probes get dirty too quickly during roasting to work effectively. Using an air-pressure manometer is the best current option to monitor and maintain consistent airflow batch to batch. However, the relationship between pressure and flow will shift slowly as the ducts get dirty, so frequent chimney cleaning is critical.)

High-resolution gas manometer: 

Most roasting machines come with small, cheap analog manometers that offer imprecise gas-pressure measurements.

I recommend replacing your stock analog manometer with a high-resolution digital manometer. Analog manometers may be aesthetically pleasing, but they make discerning precise readings too difficult. 

Proper probes and probe locations: 

To be a best sample coffee roaster by today’s standards, one needs better green, lighter roasts, quality data collection, precise controls, and software to track and analyze the data.

To ensure adequate data collection, insist on having a bean probe and an environmental probe, each with diameters of 2.5 mm– 4 mm. An inlet-temperature probe is helpful but not critical. 

The optimal bean probe location in most machines is as follows: 

• The probe’s tip should be 3–5 cm from the inside of the machine’s faceplate. 

• The probe’s tip should be 3–5 cm from the inner drum edge.  (2 cm is ok for machines with a capacity of 1 kg or less.)

• The probe tip should be in the heart of the bean pile, even when roasting very small batches. If the probe is too high in the drum or too close to the center axle, it may not be immersed in the bean pile of very small batches. Proper probe location should provide quality data for batches as small as 20% capacity.

Paying for a machine: 

Manufacturers typically require the buyer to deposit 50% of the machine’s price upon ordering, with the balance due upon shipment of the machine.

The problem with such arrangements is that once a manufacturer has your deposit, he or she may lose motivation to deliver your machine on time.

Salespeople routinely promise a machine in three months, secure a deposit, and then ship the machine six to nine months later, claiming unavoidable delays.

The buyer is helpless as he or she pays rent on an empty roastery and loses money waiting for the machine to arrive. I have seen such delays happen on fully half of my clients’ orders.

I strongly suggest insisting on a sales-contract clause guaranteeing delivery by a certain date, with a penalty against the manufacturer for late delivery.