The curve compare feature allows you to overlay several profiles on one screen to visually analyze similarities or differences between multiple roasts. Many roasters will use this to compare a single roast to a previous template and assess how close they were able to match landmarks and times to each event.
In our production roastery, we've found additional ways to utilize Curve Compare as an effective tool in quality assurance. We will often underlay roasts for one green coffee from several weeks or months to evaluate how a green coffee's age is changing how it takes on heat.
Coffees that have been in your inventory for several months will contain less moisture, as a result of long-term storage and evaporation. This decrease in the water content will mean that the dry phase will become shorter over time. When we compare several roasts from when we initially purchased a green coffee to roasts after it's been in our warehouse for over three months, we will tend to see a 30-second decrease in the Dry End landmark. To account for this, we will adjust our initial fuel setting to a lower gas pressure, applying more gentle heat to these dryer seeds, and try to hit the Dry End target closer to where it occurred in the original profile.
The Curve Compare above shows a roast curve in red for a Peru Cajamarca from January, when it was first purchased, and a curve in blue for the same coffee roasted six months later. All events occur about 30 seconds earlier for the older coffee. In the fuel values at the bottom, you can see that we use a much lower initial fuel setting (a kind of "faux soak") at the beginning of the roast to apply more gentle heat to the older coffee beans.
Another use case for Curve Compare comes up when we roast pre-blends and have to change out components. Our espresso and cold brew blends are all pre-roast blends that we carry year-round. The seasonal availability of green coffee means that we swap components in these blends 3-4 times each year. Using Curve Compare, we can easily see how fresher coffees are changing the way that a blend is behaving in the roaster. Combining those observations with our notes at the cupping table, we can decide how to make changes to the blend profiles to ensure a consistent flavor experience for our customers.
In this comparison, our Cold Brew pre-blend from a few months ago is shown in red. In blue, a recent curve of the same blend with a new replacement, which we roast for longer to the same finish temperature to achieve the same flavor profile.
How else can Curve Compare help you better understand your coffee? We compare curves from different seasons of the year to evaluate the impact of extreme swings in temperature (hello, Minnesota winters!). This helps us fine-tune our pre-heat and between-batch protocols for consistency year-round. Curve Compare also offers insight as to how changing our batch sizes impacts time to events for a single coffee, helping us dial in full, half, and small-sized batch sizes for our most popular coffees.
This is one of the many tools built into RoastPATH that puts roasters in control of their data and their coffee quality.
