Force as opposed to Agtron for measuring roast development

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
day
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#1: Post by day »

Well, recently I found a great local roaster. He has taken a lot of time talking to me, and I really enjoyed an Ethiopian konga he has been brewing. I bought another bag last week and it lacked some of its berry flavor from the previous roast (starting to develop now 8 days out) but I immediately noticed when I ground in my Pharos that it was slightly harder to grind. I asked him about it and he had changed his fan and such to alter the roast and he wasn't as happy with how it turned out. He was cleaning his roaster at the time or I am sure he would have pulled his notes out, but it got me thinking, instead of using color couldn't we use some sort of crushing device to measure force, or even a grinder kept at the same grind setting with some way of measuring starting torque to refer to Roast development?
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yakster
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#2: Post by yakster »

Hand grinding for me has given me feedback on degree of roast, but because the density of different coffees varies I'm not sure that you could come up with anything but a relative scale. How much does a hardness tester go for? Maybe Socratic would want to take this up?
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TomC
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#3: Post by TomC »

day wrote:Well, recently I found a great local roaster. He has taken a lot of time talking to me, and I really enjoyed an Ethiopian konga he has been brewing. I bought another bag last week and it lacked some of its berry flavor from the previous roast (starting to develop now 8 days out) but I immediately noticed when I ground in my Pharos that it was slightly harder to grind. I asked him about it and he had changed his fan and such to alter the roast and he wasn't as happy with how it turned out. He was cleaning his roaster at the time or I am sure he would have pulled his notes out, but it got me thinking, instead of using color couldn't we use some sort of crushing device to measure force, or even a grinder kept at the same grind setting with some way of measuring starting torque to refer to Roast development?

You might get a rough idea, but nothing close or dependable. And that would have to be on the exact same crop/harvest etc. Even within one type of coffee you're going to encounter variable bean sizes and densities to a certain degree. It's just part of dealing with an agricultural product. The cellulose makeup of each individual bean would likely vary enough to make useful measurements difficult. Cherries receiving more sunshine will usually store more sugar and ripen faster than those under its own foliage. All that taken into account will give you different levels of seed development and structural makeup. This doesn't even include the variables like the occasional peaberry in a normal lot, or if they're a natural processed coffee.

Of course, there's the old school (and free ) method, chomp a few beans. Your teeth will give you some feedback that you can compare (roughly) if you're doing subsequent roasts.
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day (original poster)
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#4: Post by day (original poster) »

TomC wrote:You might get a rough idea, but nothing close or dependable. And that would have to be on the exact same crop/harvest etc. Even within one type of coffee you're going to encounter variable bean sizes and densities to a certain degree. It's just part of dealing with an agricultural product. The cellulose makeup of each individual bean would likely vary enough to make useful measurements difficult. Cherries receiving more sunshine will usually store more sugar and ripen faster than those under its own foliage. All that taken into account will give you different levels of seed development and structural makeup. This doesn't even include the variables like the occasional peaberry in a normal lot, or if they're a natural processed coffee.

Of course, there's the old school (and free ) method, chomp a few beans. Your teeth will give you some feedback that you can compare (roughly) if you're doing subsequent roasts.
I have always understood that the bean to bean variance would cause a range of color as well, and of course a peaberry finding its way into an AA kenyan lot would end at a very different color than the rest of the beans. Naturally, when grading color we have to grind several beans to get both internal/external color as well as the average of bean color.

As i understand it the color develops as cells break open and begin to roast, which is all dependent on temperature, I dont really see why it wouldn't be possible for a relationship to exist between average crushing force (say 25 beans laid flat on a plate and measure the force required to crush) and average color since they both change relative to the drop temperature. If, in fact, such a relationship exist and is dependent on the sugar and overall cellulose make-up of the bean, it seems to me that there is a real possibility that the average crushing force may be able to be linked to how the beans will extract when ground. This, in turn, could potentially provide useful data when accurate color grading is not available, but, more importanly, if a relationship exist between crushing force and solubility it might even help when dialing in a particular roast.

Ultimately, I think I hear what you are saying, but I dont really see how the variability you mention are significantly different than the same variability present when using color as a benchmark of roast development.
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day (original poster)
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#5: Post by day (original poster) »

One more follow up thought. I have certainly done and read of users changing brewing temperature and parameters based on roast color. Would it not seem logical then that a similar, but maybe more precise, relationship exist with crushing force and brewing parameters?
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#6: Post by TomC »

day wrote:
Ultimately, I think I hear what you are saying, but I dont really see how the variability you mention are significantly different than the same variability present when using color as a benchmark of roast development.
Most roast color measurements are used with ground coffee for the most part. It's homogenized and averaged that way. Using a roast color meter for whole bean (although useful to some), only shows the delta of outer bean to inner bean development.
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day (original poster)
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#7: Post by day (original poster) replying to TomC »

That's why I wrote : "Naturally, when grading color we have to grind several beans to get both internal/external color as well as the average of bean color."

Several was perhaps a bit of an understatement but I meant that we would similarly be looking at the force to crush multiple beans to get average roast profile information. It may not be meaningful but it certainly feels meaningful on the Pharos.
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