Beany business

Author: Jamie Zachary

A bit of art, a dash of science … so much goes into creating that perfect cup of coffee or sweet, delicious chocolate. 

And it all starts with that diminutive bean – or more specifically, how it’s handled before it ever lands in your hands. 

We recently sat down with Caroline Richard, senior process engineer with Solex Thermal Science, to break down the role pre-heating plays in production process of beans, nuts or cereals and grains, including how new applications with indirect heating technology is giving producers a competitive advantage. 

Solex: What happens to a bean during the roasting process? 

Caroline: At a high level, the bean loses moisture and gains temperature. For example, most dried green coffee beans are packaged and shipped to roasters with eight to 12 per cent moisture. Yet by the end of the roasting process, this will be around two to four per cent. 

Solex: So then why would you want to pre-heat beans prior to roasting? 

Caroline: It can contribute to a more efficient production process. No matter what kind of roast we’re talking about, it's more cost effective to raise the bean’s temperature prior to roasting than roasting cold, wet beans. If we go back to coffee, roasting happens at temperatures upward of 200 C (400 F). But before beans can be roasted, moisture needs to be removed and the bean itself needs to be raised to the roasting temperatures. And that can’t happen until the beans are hot enough to essentially “sweat it out” – until you’ve spent the necessary energy to raise the temperature enough that the moisture is pulled from the beans. Extracting that moisture is energy intensive. It’s also what takes the longest. And trying to do this from storage in a roaster is inefficient. The roasters are effectively doing double duty both pre-heating and roasting the beans. By pre-heating, you can fast-forward to the roasting process quicker and more economically. 

Solex: Wouldn’t the roasting process also then be quicker? 

Caroline: Absolutely. Because we can reduce the bean’s moisture content and/or raise its temperature in advance, it takes less time to roast. For example, imagine we’re looking at a typical coffee roasting cycle of 12 minutes. We can take care of up to the first five minutes, which is the heavy lifting part of creating consistent temperature and moisture levels, as well as stable product properties. And by doing so, we’re essentially debottlenecking the roasting process. 

Solex: If you’re spending less time roasting, then wouldn’t you be spending less on energy? 

Caroline: Yes. And operating costs because the process doesn't take as long. The expensive part comes when you’re extracting the moisture. That’s what takes the most amount of energy. It’s also what takes the longest. While traditional tray dryers upstream of roasters can take upward of 12 hours to achieve, Solex can do the same in four hours. We use indirect heating by conduction to heat the beans. That process uses drastically less energy than tray heaters that rely on hot air. In fact, we only use small amounts of air to wick away the moisture instead of relying on air for heating purposes. Once the beans are dry enough, the energy costs for roasting are pretty reasonable. 

Solex: But what if my recipe dictates that I retain that moisture before it goes into roaster?  

Caroline: In applications where producers want to pre-heat their beans but retain their moisture, we can still effectively raise the temperature to the point just before roasting, and then inject steam to trap that moisture from escaping. 

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Did you know? 

The Solex heat exchanger also offer the ability to uniformly heat and dry beans, nuts, cereals or grains. Visit our Food Products page for applications, videos and more. For Coffee or Cocoa, download our product handouts. 

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