HCCI – HunterLab Coffee Color Index measures the reflectance of ground coffee products at 640 nm, which is optimal for defining the degree of roast.
HCCI works best for measuring during the roasting process, taking the coffee product to a consistent end point.
HCCI = [HCCI_slope * R%(640 nm)] + HCCI_offset
where default coefficients for HCCI_slope = 1.958 and HCCI_offset = – 3.32.
HCCI* comes with a user-adjustable bias and offset in each setup to allow display in agreement with existing instruments.
HCCI values are typically displayed to 1 decimal place.
The HunterLab ColorFlex EZ Coffee meter comes with a built-in correlation to report HCCI – HunterLab Coffee Color Index, SCAA # and SCAA Roast Classification, all used to quantify the degree of coffee roast.
FAQ: “Can the HCCI Index be used for any application that has a product that goes from dark brown to light brown? Like a contrast meter?”
In theory, yes; in practice, maybe.
HCCI, implemented in the CFEZ Coffee Meter, does have a user-configurable offset and gain that your customer can tailor the output value to their process color.
Be cautioned, however, that this metric was optimized based on the reflectance at 640 nm. This is the spectral point of greatest change for the intended application of quantifying coffee roast color. Your customer’s dark-to-light brown process should be similar but they should look at the reflectance curves for a range of their product color to verify 640 nm represents a significant change point with their process.
As alternate metrics, L* lightness value, b*/a* ratio or % Strength may also work to color quantify their process while being more robust as a metric and in more general use for all colors.
FAQ: “Are there limits to HCCI values for ground coffee?”
Again, there is theory and practice at work here. In theory, a perfect black with a value of 0% reflectance at 640 nm defines a corresponding HCCI value of 0. So this would be the theoretical darkest HCCI value that could be measured, darker than charcoal. There is no upper limit but anything over 25% would be odd.
In practice, it would be unusual to be roasting to a target color far outside the range of the visual SCAA color standards for ground coffee of Very Light (approximate HCCI ≈ 22 to Very Dark (HCCI ≈ 1).