A better bean

Pre-heating technology gives roasters added flexibility with out-of-spec beans

Author: Jamie Zachary

In the world of coffee beans, weight equals money.  

Too much weight, or what we’d refer to as moisture content, and the beans can spoil before they even get to the roasting process. Too little and it can compromise flavour when the beans comes out of the roaster. 

For exporters in the world's “Bean Belt” region that includes Brazil, Vietnam, Columbia and Indonesia, green beans are harvested with around 45 to 55 per cent moisture. By the time those beans are shipped to roasters, they usually contain moisture levels ranging from eight to 12.5 per cent. (Anything above 12.5 per cent and the International Coffee Organization says the beans are more like to spoil.) 

But over-drying also has unintended consequences. Drying requires energy, and energy costs money. Coffee also sells by the pound, meaning over-dried beans fetch less in a market where every cent counts. 

Additionally, over-drying has the unintended consequence of leading to loss of colour, which leads to lower liquor quality. The International Trade Centre notes that when moisture levels drop below 10 per cent, aroma, acidity and freshness begin to fade. At under eight per cent, they have all but disappeared. 

Mission possible 

The challenge for buyers then lies in fetching a quality bean that doesn’t break the bank. 

Advancements in bulk solids thermal exchange is giving commercial roasters unique opportunities to better accept out-of-spec beans at lower prices without adversely impacting the final recipe. 

“Indirect heat exchange technology provides roasters with a sustainable solution where they can uniformly raise the temperature of their beans using surplus plant energy and either reduce moisture or use steam to trap that moisture at whatever level they want prior to roasting,” says Pedro Moran, Global Director of Food Products for Solex Thermal Science, a global leader in bulk builds thermal exchange. 

“By doing that, roasters are able to accept coffee at a wider range of specifications. They are able to buy green coffee beans with a bit of out-of-specs characteristics at a relatively lower price, increasing their profitability while maintaining the overall product quality.” 

How does it work? 

Solex uses water, steam or condensate as heat transfer mediums inside heat exchanger plates that the beans then uniformly pass by and come out with a consistent temperature and moisture. 

“Our proprietary thermal modeling software pre-determines the bean-to-bean temperature profile, moisture profile and drying rate, which is then used to predict the optimal control settings for specific beans,” says Moran 

Because the mechanisms of raising the temperature and/or drying are separated within the exchanger operators can essentially select the optimal control parameters for each type of bean or recipe blend. 

“We can dial in a recipe and offer the operator complete temperature control. If they want beans with five per cent moisture at 165 F, we can give that to them consistently, day after day,” says Moran, adding Solex doesn’t depend on air to heat or dry, and therefore is not impacted by ambient conditions and reduces the overall roasting air emissions footprint 

Want to learn more? Download our Coffee and Cocoa product handouts. 

Ready to talk specifics? Contact a Solex team member today. 

Did you know? 

In addition to coffee. the Solex heat exchanger is also able to heat and uniformly dry cocoa beans, nuts, cereals and grains. Visit the Food Products page for applications, videos and more.  

This entry was last updated on 2023-1-17

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