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Roasting Basics: Tips for Roasting Samples

When you get a sample of green coffee, how can you determine that it is good grain? How to choose the best roasting profile? Showcase coffee to potential customers?

And how to do it as efficiently as possible, with minimal cost and maximum accuracy?

The answer to all these questions is simple: frying the samples.

Aysatu Diallo, European Lab Coordinator and Sales Manager at Caravela Coffee, uses IKAWA digital micro roaster to sample the samples. Photo:  IKAWA

What is Sample Roasting?

Sampling (sampling) roasting, in theory, is a fairly straightforward process – it is roasting a small sample of green coffee. And there are several reasons why you should do this.

  1. Evaluate the quality of green coffee.

The main purpose of roasting samples is to objectively evaluate the quality and uniformity of green coffee, which is beneficial to everyone in the supply chain.

For green coffee exporters, importers, and polarists, sample roasting is an important part of selling and buying green coffee. “This is how you determine the quality of a particular coffee,” says Moz “Mani” Keleher, chief roaster at Ancoats Coffee Co. in Manchester, UK – “You take a small amount of coffee, and this small amount will represent the entire lot (batch) of coffee. You are trying to understand this coffee, turn it from green to roasted, within the set parameters. ”

Moreover, it is effective. Ed Brown, UK sales manager for Ally Coffee, says: “You can’t tell what the coffee will taste like when it’s green and you don’t want to buy a bag of coffee and roast all 50kg… you can just roast 50g at a time, and that will be enough to appreciate coffee. ”

With the help of sample roasting, companies can make key purchasing decisions. But sample roasting is also incredibly relevant in countries of origin. Frying and caping can be done by producers or buyers themselves, who will then share their impressions with the farmer, as this is a source of valuable information on grain quality. In turn, this opens up new avenues for improving the cultivation and methods of coffee processing.

Mauricio Contreras, a Q-grader from El Salvador, fries a sample of coffee at Cooperativa Cuzcachapan to evaluate its quality. Photo by  Dennis Tan Flickr CC BY-SA 2.0

  1. Choose the perfect roasting profile.

Roasting a sample of coffee, you have 2 goals. First, you want to roast each coffee equally so that you can compare it on a fair basis. Second, you want to fry it so you can choose the best profile.

But when you roast coffee for consumption, you have a new set of goals: to emphasize the best features of coffee and to create a product that pleases consumers. To do this, you need to experiment with different roasting profiles. Again, sample roasting is the most effective for this purpose.

  1. Capture sales or training.

The approach will be different if you are frying for consumers, customers, for capturing or training for staff. In this case, you want each sample to emphasize the best features of coffee. This means that Ergacheff’s Ethiopia should be fried to emphasize its sparkling acidity or to reveal the sweetness of Bourbon’s natural finish.

However, although the goals are different, the principle is the same: you roast a small sample of coffee so that it can be valued at no extra cost.

Samples of green and roasted Brazilian coffee; the green sample will be checked for visible defects, color and size stability. Photo by  TJ Ushing / UC Davis CC BY-SA 2.0

The way coffee goes from green samples to sale.

Let’s say you ordered the samples of green grain you plan to buy. You will be sent standard packages of 300 gr to 2 kg. Such samples are large enough and can be divided into smaller ones (within 50-200 gr) and only then can the samples be fried.

Next, you want to roast all your samples equally to determine the overall taste of the coffee. It is important that your roasting profile does not hide or highlight the characteristics of the coffee. “You want to taste the grain, not the fry,” says Mani. “You focus on neutral taste. Determining the best taste and the right profile will be later. ”

Samples should be stored within 8-24 hours after roasting. At this stage the fryers check the grain for defects, especially those that are not noticeable in the greens. “Taste defects, such as phenol, mold, or contaminants, can often only be detected after roasting,” says Roland Glu, Chief Roaster at Has Bean Coffee in Staffordshire, UK.

Once you find the coffee you want to buy, you can switch to another type of roast. Now you are trying to choose the best roasting profile. Of course, “best” is a subjective concept; each roasters will want to emphasize different features in a particular coffee.

Once you’ve found your profile, it’s time to move to production roasting. For commercial roasters, the whole process, from getting a sample to launching new coffee at retail, can take 1-3 weeks. It depends largely on the speed at which you bid and buy coffee. “You want to deal with the sample frying fast enough,” Mani says, laughing. The coffee is over so fast!

And then the process starts again! Polar is constantly on the lookout for coffee, and they also regularly do sample frying to check the quality.

“Here at Colombo, we make samples of every new coffee we get at least once a week,” says Chad Whitby, chief roaster and assistant general manager at Colombo Coffee in Durban, South Africa. He emphasizes that the sampling is very strict, adding: “There is a certain protocol for stability.”

Ethiopian producers check the uniformity and consistency of coffee during the caping. Photo by  G. LaRue / USAID Flickr , United States Government

Sample roasting: process.

The process will depend on your goals, if you want to evaluate and compare the quality of green coffee, it is very important to roast consistently. You won’t be able to exactly compare two coffees if one is more sophisticated.

This means that all the frying elements, from airflow, gas and time, to the exact weight and labeling of the samples should be monitored. You do not want to mix your coffee (and data)!

And be sure to visually evaluate green coffee for defects before you start roasting the sample.

According to my interlocutors, a typical sample roast on a traditional drum roster (more on that!)  Can look something like this:

0:00:  When the roaster is heated, a sample of green coffee is loaded into the drum and a timer is started.

~ 1: 00-1: 30:  The camera temperature should be raised and the air flow lowered. The temperature of green coffee at this time itself increases due to the “reversible phase.”

~ 3:00:  Water evaporates from green coffee, so steam out should be provided.

~ 3:30:  Usually check for color: the grain should turn yellow between 3: 00-4: 00.

~ 4:00:  Coffee is noticeably yellow. Humidity drops from 10-12% to 1.5% and “caramelization” begins (Maillard reaction).

~ 6: 30-7: 30:  Depending on the coffee, you will begin to see and hear the first crack. It is useful to check the smell if there is an opportunity to know that the coffee is not burning. You may need to increase the airflow to get all the steam or smoke out of the rotor. Otherwise, they can affect the taste of roasted coffee.

~ 8: 00-9: 30:  90-120 seconds after the first crack, the frying is complete. Even if you usually fry up the second crack, it should be finished before you can evaluate the quality of the green coffee. The temperature must be maintained at all times to avoid baking.

Finally, turn off the roaster and pour the grains into the cooling tray. Coffee can now be analyzed. In addition to the caping, you can check the weight change and color on the spectrometer.

A traditional two-reel sampler. Photo:  Stephen Brooklyn Wikipedia CC BY-SA 3.0

Which equipment should be used for sample roasting?

We looked in detail at the process of roasting samples on a traditional drum rotor. However, this is not the only option.

  • Drum Rosters: A Traditional Approach.

Traditionally, a roaster with several drums is used for roasting samples.

“The sample rosters are designed for very small batches – within the range of 30-300 g,” Roland says. “Many of them are able to roast several batches at a time, having two, three or four drums, all of which are usually connected to one drive shaft. The algorithm of drum samplers is usually very similar to production ones. ”

In this method, the coffee is roasted mainly due to the heat transfer that occurs during the interaction of air flow and heat from the drum. The process during which grains receive heat from the inner surface of the drum is called conduction.

The airflow is generated by the holes in the drum and is controlled by the levers on the panel. Heat provides the flames inside the rotor. Grain is constantly moving due to the rotation of the inner drum.

An important aspect is air flow management, as it affects heat transfer efficiency and also protects the grain from smoke and defects. Therefore, it is worth noting that drum samplers often have limited air flow control.

Coffee roasted on a IKAWA digital sample roaster. Photo:  IKAWA

  • Digital samplers: fashionable technologies.

In recent years, new tools for sample roasting have become available, namely digital micro-routers. Sample roasting on traditional raster can take a lot of time and resources. Sample evaluation is one of the most important activities of the polar, but sometimes it becomes too routine.

Digital micro-roster profiles are programmable, allowing consumers to roast coffee consecutively using the same profile each time. They are often portable and use fluidized bed technology. This means that the coffee lies on a “layer” of hot air that is constantly in motion, so roasting is due to convection.

The results obtained on the digital micro-roster can be copied and sent. “Creating and sharing digital roasting profiles allows you to use common language at all stages of the supply chain,” says Alex Georgiou, Head of Marketing at IKAWA. “You can send a frying profile to an email that minimizes discrepancies.”

  • Home roasting: an approach for small volumes.

While many polarities work with larger-scale digital or drum routers, others opt for a simpler and more affordable method: a home desktop roster.

Small in size, they are perfect for frying samples. They are also more accessible to farmers who use them to evaluate the quality of coffee and low-budget polarities. And, of course, they are ideal for home-based fryers who want to find the best grain profile, with minimal losses.

Behmor 1600 desktop roasters, which Behmor provides to cooperatives around the world for free, so that producers can roast and roast their coffee. Photo:  Behmor

You may be evaluating green grain, looking for the best profile, or arranging for a cap – sampling is useful in many cases.

So remember: fry the samples according to your goals. Select the equipment you want. And carefully monitor and record all variables.

Author: Sierra Burgess-Yo.

Translation: Anna Polstiankina.

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