What do the differences in bean gloss mean?

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
noah

#1: Post by noah »

If I roast the same beans (in my case ~1/2 cup Brazil Ipanema Dry Tree Process) to the same point (ceased right at the start of second crack) and the first batch has a nice complexion, almost like an eggshell paint, while the second is completely flat, what can I learn from this? The second batch was a slower (a little over 16 minutes).

Is the lack-lustre appearance of the second batch indicative of excessive or insufficient heat at some point during the roast, and if so, which phase?
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another_jim
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#2: Post by another_jim »

The luster of the beans just after the roast is based on how much oil is on the surface (matte, eggshell, semi-gloss, high-gloss, oildrops :wink: ).

When you roast to the second crack, the beans will be high gloss inside the roaster, but will reabsorb the oils and be matte as they cool. Then, depending on exactly how far you've gone, the oils can reappear after a few days.

The association of oils and second crack is not graven in stone. In a slow roast, the 2nd starts at a lower temperature than for a fast roast, and fewer oils appear.

These two factors, roast speed and reabsorption could explain your gloss difference.

For roast quality, it's better to examine the beans for wrinkles and cracks, rather than sheen. A really good roast to the first pops of the second should give you botox smooth beans.
Jim Schulman

noah

#3: Post by noah »

What do the small cracks in the beans indicate (near the ends of the beans mostly), and how do I fix this?
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another_jim
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#4: Post by another_jim »

It depends. Here's a pic, 3 days post roast, of a wonderful tasting coffee that roasts really ugly -- the grade 5 dry process Sidamo Bonko
Image

As you can see, there's chaff, a huge variation in roast color, some oil spots. There's even one cracked tip (top left, 2nd bean down). In this case, you can see by the color, that it's a near quaker, and damaged from the get go. The other beans are uncracked and relatively unwrinkled, showing that the roast went well. I'm putting up this pic so that people don't get too perfectionist in their roasting (especially since the easiest way to get a perfect looking bean is to bake them a bit and get a flat tasting coffee)

But if a lot of beans are cracked, especially ones that are not discolored, then you shoiuld suspect that you either over dried the beans, or that the drum surface got too hot.
Jim Schulman

noah

#5: Post by noah »

I see. I did not get any beans that quite looked like that, but several that looked like the bean on the upper right hand side of the photo, with small cracks. Is this also indicative of excessive drying? Thanks for taking the trouble to post that pic!
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another_jim
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#6: Post by another_jim »

If small cracks radiating out from the split are a problem, then my roasting sucks. They seem to increase as one gets further into the second crack. When I was talking about an uncracked, smooth surface, I was talking about the rounded side of the bean, on the opposite side of the split.
Jim Schulman

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triptogenetica

#7: Post by triptogenetica »

another_jim wrote:If small cracks radiating out from the split are a problem, then my roasting sucks.
Good! If you're saying that, Jim, then maybe my popper roasts aren't so bad after all.

(The coffee tastes good, but i do have those little cracks too)...

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farmroast

#8: Post by farmroast »

Some of us found the Ipanema tree dried to be a little on the dry side, I measured 10% YMMV(your moisture may vary ). If your flatter/oilier roast might have been slower in the start it would seem that more oil could be drawn to the surface later in the roast and if there was a little less moisture available might have somewhat limited some flavor development.
LMWDP #167 "with coffee we create with wine we celebrate"