May 5, 2020

Responding to Coffee Bean Weight Loss in Roasting

Bean weight loss can cause profitability to plummet and also, in its own way, affect roast profiles – and it’s all down to moisture content. However, roasteries can control moisture content in green coffee and protect themselves from significant weight loss.

We’re going to explore what bean weight loss is, how bean weight loss affects roastery profits, and how to control bean weight loss.

Lee este artículo en español Cómo Manejar la Pérdida de Peso Del Café Durante el Tueste

What Is Moisture in Green Coffee?

Water is a component in all living organisms. Coffee beans, the seeds of coffee cherries, are no exception.

Green bean moisture content in specialty coffee usually varies from 10–12%, although the International Coffee Organization accepts a broader range, between 8–12.5%.

Low moisture content in a green coffee (under 10%) can result in a reduction of cup quality, while high moisture content (over 12%) puts the coffee at risk of mold and greater bean weight loss after roasting.

Green coffee is a living plant matter so it will lose moisture to its surroundings, causing moisture levels to fluctuate. Therefore, the correct storage of green coffee beans is integral to maintaining a steady moisture content.

You may also like: How Does Moisture Content Affect Coffee Roasters?

How Can Bean Weight Loss Affect a Business?

During the roasting process, coffee beans will lose the majority of their moisture, and the weight of the coffee beans will drop because of this. It’s not uncommon for a batch of coffee to lose around 16% of its weight during a roast due to the reduction in moisture.

Roasted coffee is the end product that is sold by weight. Although roasted coffee has a higher value than green coffee, the larger the discrepancy between the green coffee weight and roasted coffee weight, the greater the economic loss is made. 

So, the higher the initial moisture content in the green coffee, the more weight there is to lose during roasting. The management of green coffee moisture content is, therefore, key to profitability.

Although small percentages in weight loss can seem minute or potentially irrelevant, this is not the case. If there have been continual significant drops in weight through roasting, this can lead to greater financial losses overall.

Weight loss in roasting coffee is unavoidable. However, this can be managed.

What Causes Bean Weight Loss & How Can It Be Controlled?

Roasters and businesses can control bean weight loss by managing as many aspects as possible throughout the coffee supply chain. This will help minimize the inconsistency during roasting, and hopefully, create more predictability on how much bean weight loss there will be.

Buying & Transporting Coffee: Controlling Moisture Content

Roasters may not be in the best position to implement quality control during production and transportation, but they can make sure moisture content is in the contract they sign with buyers.

Agustina Román, Q Grader and manager of Ninina coffee roastery, in Buenos Aires, explains that communication and consistency are key when buying and storing coffee. This, in turn, will help control inconsistencies throughout the rest of the roasting process.

First, determining and establishing a maximum and minimum moisture content in a contract is beneficial to creating an understanding as well as a requirement from producers and exporters. For example, at Ninina, Agustina allows a maximum of 12.3% moisture content in the green coffee.

Controlling the levels of moisture is not only relevant for how coffee responds to roasting but also the quality of the coffee. For example, high levels of moisture can produce mycotoxins from mold, such as Ochratoxin-A, which can be harmful to consumer health. 

When green coffee arrives at the roastery, it must be weighed and have its moisture content measured. If moisture exceeds the agreed range from the contract, this should be communicated with the exporter and resolved.

Coffee is hygroscopic, which is why hermetic and sealed bags are always the best option for transporting and storing coffee. 

Storing Coffee: Controlling Moisture Content

Green coffee will respond to temperature and humidity in warehouse and storage rooms. Roasters must, therefore, ensure that they are storing coffee to protect it from these conditions and prevent fluctuating moisture content.

If coffee is packed in hermetic storage bags, this will help prevent the coffee from losing moisture to the air. 

Agustina also says, “Once the coffee arrives at our facilities, we have a warehouse with controlled temperature continuously circulating air at 20ºC/68ºF.”

As well as keeping control of temperature and humidity, keeping bags raised off the floor on small pallets and rotating coffee bags will increase the circulation of air around the coffee.

Roasting

Controlling a roast will enable you to both manage the weight loss in a bean as well as achieve the desired profile.

First, it’s crucial to understand your roaster and have a roasting routine. At Ninina, Agustina highlights the importance of consistency. Roasters follow a pre-heating and in-between-batch protocol as well as always roasting the same size batch every time. This is essential to help predict the bean’s behavior.

Second, always be aware of the moisture content in the beans before a roast. When roasting coffee with a high moisture content, you will need to apply more thermal heat during the drying phase. Depending on your roaster and your process, there are different options on how to do this that have different potential risks. You can try a higher charge temperature (not too high as this could scorch your beans); try using a higher flame during the drying phase; or opt for a longer drying phase.

Roasting your coffee dark will result in a higher loss of moisture, and therefore more bean weight loss. Light roasting will mean less moisture loss and therefore less weight loss. Lighter roasts can, therefore, be helpful in increasing profit margins. However, always keep in mind the overall flavor of the coffee. Stopping a roast early to prevent moisture loss is never advised, the development of the flavors should always be the priority.

Maintaining a reasonable content in green beans during storage is a challenge, but tackling it is essential. Make sure to request samples, check the moisture level of green beans when you receive them, and store the beans well to keep that moisture content stable. Build a good relationship with a supplier you trust, so that if there is an issue, you can resolve it quickly.

Enjoyed this? Check out How to Measure Moisture in Parchment & Green Coffee Beans

Featured photo credit: Jean Pierre Flores. All photo credits: Nicole Motteux, Fernando Pocasangre, and Jean Pierre Flores.

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