Since the dawn of commercial coffee making, stones, rock fragments, shards and other detritus have been the mortal enemies of grinder burrs. The sound of one itsy bitsy stone on rapidly revolving metal chills the spine.
While the industry has developed a broad range of “destoners” to sort out these damage-causing pebbles, nearly all of those machines are designed to live in industrial mills, warehouses or roasteries.
Now, a research team at the Singapore University of Technology and Design has come up with a mechanical solution that would put destoning in the hands of busy baristas or cafe operators.
While nowhere near commercialization, the novel solution involves the use of microphones placed strategically within the grinder that capture the machines acoustic profile in real time.
The method employs an algorithm called empirical mode decomposition (EMD), which breaks down complex sound signals into simpler components known as intrinsic mode functions (IMFs).
In isolating IMFs, the system can accurately pinpoint the presence of stones within a grinder in which coffee beans are merrily rumbling amidst the whir of the burrs. The system also involves programmable processors for real-time data analysis called field programmable gate arrays (FPGA).
“Stones produce transient, distinctive acoustic patterns that EMD easily recognises, even amidst background noise,” study author Teo Tee Hui said in an announcement from the university. “We specifically chose FPGA for its real-time processing capabilities and cost-effectiveness — crucial for adoption in small-scale commercial coffee settings.”
The study was published in February in the MDPI journal Applied Sciences.
The research team said it is continuing to refine the method, given the challenge of detecting tiny fragments, whose acoustic signatures can overlap with, or become masked by, coffee beans within a grinder.
“Ultimately, our goal is straightforward. We want to prevent stones from ever damaging a coffee grinder again,” Teo said. “By developing a reliable detection method that enhances the efficiency and longevity of coffee grinders, we could benefit cafe operations and the coffee industry as a whole.”
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