Roasting coffee is a complex process, and mistakes are easy to make. Without the proper oversight, coffee can come out overdeveloped, underdeveloped, scorched, or baked – all of which can ruin the flavour of entire batches. Commonly known as “roast defects”, these mistakes typically occur when roasters lack information on what’s going on during key points of the roast.
Tipping and scorching are two of the most common defects roasters will face. Unlike other defects, such as baking or underdevelopment, both tipping and scorching are easy to spot. They appear as scalds or burns on the surface or ends of the beans, indicating it has suffered physical damage.
Even for the most skilled roasters, it can be difficult to achieve a consistent roast every single time. So how can you avoid these roasting defects? To learn more, we spoke with Hannah Whitton, who is Head of Coffee for Craft House Coffee, in South East England.
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Sign upUnderstanding the difference between tipping & scorching
While they are similar defects, there is a visual difference between tipping and scorching. “Scorching is a result of the coffee beans being exposed to excessively high temperatures early in the roast, or because the batch size is too large,” explains Hannah, who has 12 years of experience in the industry.
A batch size that is too large can lead to too much conduction. The beans will lack space and remain in contact with the surface of the drum for too long, which results in blistering. Essentially, scorching happens when the drum is too hot. This may be a result of charging the temperature extremely high or having the flame too high at the start of the roast.
When the beans are dropped into the roaster, they scorch because the conductive heat transfer is too large for the bean surface to handle. It is a bit like cracking an egg on a stove or burning the outside of a marshmallow on a direct flame. Rather than taking the time required to break down the cell structure, it is a flash impact on a small surface area.
“Scorching can also occur when the rotation of the drum is too slow,” Hannah adds. This means there is not enough kinetic energy to lift the beans off the drum. As a result, they stick to the bottom and burn.
The best way to determine whether scorching has occurred is to check the beans for burn marks on the surface. These often look like tiny round holes. “I’ve always thought scorching made the beans look like Ladybird bugs with their dotted wings.”
While tipping causes the same flavour taint and visual markers as scorching, it is for different reasons. “Tipping occurs when the environment in the roaster is too hot or the drum is rotating too quickly. This results in the tips of the beans having dark burn marks,” Hannah explains.
Tipping has more to do with convection than conduction, as the beans are unable to conduct or absorb the heat fast enough and burn in a particular area. “It can happen because of overall charge temperature and air in the drum being too hot, or there not being enough airflow, which causes too much heat transfer too quickly.”
In his publication ‘Tipping and It’s Avoidance’, coffee consultant and author Rob Hoos explains the defect can happen at any time during the roast. It is due to the diffusion of the heat happening much faster at the endpoints than in the core, leading to burning the tips.
“Tipping is caused primarily by excessively hot air impacting the coffee seed where the ends are particularly susceptible. The heat will damage the softest part of the seed,” the publication states.
Identifying roast defects through flavour
Roast defects can affect the flavour of the roast in different ways. This can range from slightly obscuring flavour notes to dramatically overpowering the flavour in general. Identifying these defects and how to combat them means the desired flavours of the coffee can shine through and roasts are consistent.
Consistency in coffee roasting is key. Roast defects will interrupt the consistent and special flavours of coffee, so it is crucial that they are identified after roasting in the quality control phase.
“Tipping and scorching can cause astringent, burnt, and smoky flavours in the coffee,” Hannah says. That said, both defects can be a subtle backdrop to an otherwise acceptable or flavoursome cup of coffee. Depending on how much is within the batch, it can range from an extremely noticeable to a slightly astringent aftertaste that only someone with a trained palette would identify.
Are there prerequisites of green coffee for tipping & scorching?
“In my experience, green coffees that are naturally processed, with a larger screen size and lower density, are more at risk of scorching and tipping,” Hannah reveals. With low-density beans, the cell structure will be more sensitive to heat, increasing the risk of scorching or over-roasting.
In his publication, Rob Hoos further explains low altitude beans, even those with higher density, are more susceptible to tipping. More so, the shape of the bean has an impact, as beans with pointed tips at each end are more susceptible to tipping. He goes on to discuss that the physiological composition of the beans at the ends can be slightly different to the core due to germination, which would put the bean at risk of tipping. ‘A weakened endosperm cap could explain the greater damage that heat energy can cause relative to the rest of the bean,’ the statement reads.
Hannah’s top tips to avoid scorching include reducing your batch size, increasing the drum speed, and using a lower charge temperature. When it comes to tipping, Hannah suggests roasters decrease drum speed, lowering the initial charge temperature, and increasing the length of roast profiles.
Once the roast is perfected, roasters must ensure their coffee stays fresh until it is consumed. MTPak Coffee is conscious of the fact that more consumers are demanding sustainable packaging. We offer a range of 100% recyclable coffee packaging options 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.
We also offer recyclable degassing valves and resealable zippers, while all our inks are water-based and low in volatile organic compounds (VOCs). We are able to custom-print coffee bags using innovative digital printing technology, with a quick turnaround time. We offer a wide range of customisation techniques, including spot UV with a glossy, satin, or matte finish, embossing and debossing, as well as hot foil stamping in a variety of colours.
MTPak Coffee also offers low minimum order quantities (MOQs) to micro-roasters who are looking to remain agile while showcasing brand identity and a commitment to the environment.
