How to roast green coffee samples consistently

Nuvin Sithanen
September 22, 2022
How to roast green coffee samples consistently

Green coffee is the raw material at the core of everything a roastery does. 

Before committing to a large order of green beans, a roaster should know about every aspect of the coffee. For example, where it was grown and how it was processed. 

This can provide roasters with a better understanding of what to expect when they roast green coffee samples for the first time

Just like a chef choosing ingredients for his restaurant, a roaster will have to taste the coffee to determine whether it is the right product for their business goals. 

That said, unlike most fruits and vegetables which can be tasted raw, coffee must be roasted before it can be brewed and cupped. 

Therefore, roasters must be able to roast green coffee samples consistently, in order to learn how to unlock the inherent characteristics within. 

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An image of roast coffee beans being weighed on digital coffee scales in an article on how to roast green coffee samples consistently

What is sample roasting?

Sample roasting refers to roasting a small sample of a selected stock of green coffee. 

Sample evaluation roasting is done to analyse samples of coffee for a specific purpose, such as grading and scoring coffees to decide how much it can be sold for. It is also done to identify defects within the green beans, and help determine purchasing decisions in a roastery. 

Once a sample is roasted, it is then cupped to evaluate the potential and quality of the coffee. If a roaster is happy, they will order more. 

That said, after buying a large quantity of green coffee, roasters may want to experiment with roast profiles. They can use small samples to play with different roast profiles in order to find the right match.

Using roasting samples to determine roast profile can be an effective way to save time, money, and prevent unnecessary coffee waste

When roasting green coffee samples, some roasters choose to use a sample roaster. This is a compact version of a normal roaster, allowing roasters to manipulate certain variables on a smaller scale. The capacity of some sample roasters ranges from 50g (1.76oz) to 1kg (35oz). 

The popularity of fluid bed sample roasters has risen recently, due to the consistency they tend to provide. Fluid bed roasters use convection heat, rather than conduction or induction, pushing hot air across the coffee beans.

Traditional drum roasters are also available in small 1kg versions for sample roasting and are often cheaper than their fluid bed counterparts. 

Using a sample roaster can often make experimentation more affordable for many roasters, helping them refine their knowledge of the craft.  

An image of a coffee roaster roasting coffee in an article on how to roast green coffee samples consistently

What affects roast consistency?

Two of the main variables that affect roast consistency are charge temperature and the quality of the green bean. 

An effective sample roast should unlock the flavour potential within the green bean.

That said, when requesting samples, roasters will often receive a wide variety of beans to choose from. More so, the ability to taste a coffee’s characteristics beyond the curtain of a roast is a skill few people have. 

Those who possess and hone this skill are known as Q graders. These coffee-tasting professionals undergo rigorous testing and training and regular recalibration to earn and keep this certification

However, attaining a Q-grader certification can be expensive, but that should not serve as a barrier for roasters wishing to hand-pick quality green beans. 

Roasters can make up for this by roasting a green coffee sample to determine the coffee’s qualities – which is why consistency is so vital. 

All samples should have a standardised way of being assessed to ensure roasters are making the correct purchasing decisions. 

An image of green coffee beans being scooped into a bucket in an article on how to roast green coffee samples consistently

Green bean characteristics

When aiming for consistent sample roasts, factors such as the green bean characteristics must be considered, as this will dictate how it behaves in the roaster. 

The coffee varietal and processing method, as well as the beans size and density, will affect the way it reacts when heat is applied. 

While experience is essential when manipulating the beans, roasters have a wealth of technology they can tap into

For instance, a number of crowd-based databases collect and share information from roasters around the world. 

This allows roasters to successfully replicate roast profiles used by others if they are unfamiliar with a specific variety of coffee. 

Sample size

The chosen sample size will affect how heat is transferred to the beans. 

Every coffee roaster comes with a recommended capacity size, as determined by the manufacturer. But this is the maximum recommended amount of beans you can roast, not the optimal amount for the best results. Manufacturers may be inclined to state the largest amount possible.

It is important to note that overloaded roasters will poorly agitate the coffee beans as there will not be enough room for them to move around.

Coffee beans also expand in size during roasting, so a full drum can quickly become even more overloaded. 

Using too big of a batch size can mean that some coffee beans are over-exposed to the direct heat of the drum walls, while others are under-exposed. 

For bigger batches, roasters may want to consider extending the roast time or increasing the heat in order to scale up.

Roast time

The time the beans spend in the roaster is a key variable of the roasting process. 

Usually, roasters will look out for the first and second crack as indicators of which development stage they are at. 

The longer the bean is held in the roaster, or the higher the roasting temperature, the darker the bean will become. The darker the bean, the more bittersweet the flavour. 

As a result, roasters should consistently note down the ideal roast time for their preferred profiles.

An image of a coffee producer weighing roasted coffee at origin in an article on how to roast green coffee samples consistently

How to achieve consistent sample roasts

For a barista, a well-thought out workflow will create consistency from cup to cup.

The same applies to coffee roasters. They should design a workflow that optimises consistency when they roast batch after batch.

One way roasters can improve workflow and the consistency of their roasts is by planning their day and organising the workspace. 

For example, a chef usually has a carefully prepared mise-en-place in anticipation of service time. Roasters should aim to be just as organised. 

Having a well-organised workspace with everything at hand will not only mitigate errors, but can also save time. Additionally, having an itinerary of the day can help roasters and staff determine which equipment must be preheated. 

Preparing the roaster is an essential part of an organised workflow. The roaster should be at the same starting point each time a roaster drops a new batch. 

This ensures all the beans have the same starting point and is a variable that is easy to keep consistent. 

Additionally, roasters should check the temperature for the first batch, as well as in between batches. 

An image of multilayered coffee bag with cup of coffee in foreground in an article on how to roast green coffee samples consistently

Preserving the freshness of roast coffee is of the utmost importance. Hours of hard work and effort can be undone if the freshness of coffee hasn’t been effectively preserved by the time it reaches the consumer.

MTPak Coffee offers specialty coffee roasters a range of 100% recyclable coffee packaging options that can be fully customised to your business specifications. 

Our coffee bags are made from renewable materials such as kraft paper, rice paper, or multilayer LDPE packaging with an environmentally friendly PLA lining, all of which minimise waste and contribute to a circular economy.

More so, we give you complete control over the design process by allowing you to build your own coffee bags. Our design team is available to help you create ideal custom-printed coffee packaging for your brand with fast turnaround times of 40-hours and a quick 24-hour shipping time.

For more information on sustainable, custom-printed coffee packaging, contact our team. 

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