Drying Phase Pictorial

#1: Post by **chang00** » March 30th, 2010, 2:21 am

Since there are a few discussions regarding the drying phase, here are some pictures. The roasts are wet-processed Guatemala and dry-processed Sidamo for comparison:

In wet-processed beans, the finish of the drying stage is more easily recognized. At this stage, the extra-cellular water departs the bean, and the bean actually shrinks a bit, therefore the marbling and reticulated appearance. Due to this shrinkage, notice the chaff is loose. In the Mini500, this occurs between 150-160C. In the HotTop, it occurs around 300F:

In this Sidamo, due to beans of significantly varied sizes and dry-processing, the marbling is less apparent. The chaff is again starting to come off. It may be easier to recognize this stage by color. Again, this occurs between 150-160C with the Mini500, and around 300F with the HotTop:

#2: Post by **SlowRain** » March 30th, 2010, 10:43 am

Nice pictures!

Once the drying phase is done, what are your options? Other than looking at the beans, is there anyway to note the end of the drying phase? I know smell is one thing that is supposed to change, but, if I analyze my log, will I be able to see a change in the time-temperature relationship once I plot it on my chart?

#3: Post by **Bob_M** » March 30th, 2010, 1:46 pm

i agree these pictures are great as were your earlier ones in a previous post...do the temperatures you post represent environmental temp. or bean temp, ?

#4: Post by **draino** » March 30th, 2010, 1:59 pm

To all:

if you cannot see the beans in your roaster, how do approach this phase of the roast, i.e. how long at what temp or a gradual raise of temp from x to y? Some have said to use a longer drying pase for lighter roasts (5-7 minutes) and a shorter for darker.

David

#5: Post by **farmroast** » March 30th, 2010, 2:02 pm

Bob_M wrote:i agree these pictures are great as were your earlier ones in a previous post...do the temperatures you post represent environmental temp. or bean temp, ?

Those are BT bean temp. readings

#6: Post by **JmanEspresso** » March 30th, 2010, 2:31 pm

So, what Im thinking, for the Hottop... This stage should be anticipated, and the heater should get ramped up a little bit before the beans reach this color, so when they do reach this color, the heating element is (hopefully) already at/almost at, the higher power level?

Thats something thats been in my head on my last two roasting sessions... Anticipating the changes, so I can make up for the heating element lag.

#7: Post by **another_jim** » March 30th, 2010, 3:24 pm

draino wrote:if you cannot see the beans in your roaster, how do approach this phase of the roast

I prefer roasting by smell. There is a very distinct aroma change as the beans dry and start to roast, going the smell of boiling peas to that of bread beginning to bake. You want this to occur in the 300F to 320F (150C to 160C) bean temperature range. If it happens later, and you still get peasy smells at 320F, you need to start the roast more slowly. If the peasy smells stop before you reach 300F, you should start more quickly.

March 30th, 2010, 3:26 pm

The temperature readings are actually environmental temperature, with stock thermocouples. Both roasters are unmodified.

For Mini500, I open the vent to increase negative pressure to suction out the chaff, as at this stage, the beans have not expanded so the chaffs are looser. Once the beans have expanded, chaffs may char and become slightly difficult to remove.

For HotTop, there is not a true damper/vent, but by turning on the fan, hopefully it will achieve similar effect.

The opening of the vent and turning on of the fan also attenuate the increase in ET, so beans of different sizes can hopefully achieve similar dryness with this slowing of increase in temperature, for the actual roasting to occur over the next few minutes.

#9: Post by **another_jim** » March 30th, 2010, 3:55 pm

draino wrote:Some have said to use a longer drying pase for lighter roasts (5-7 minutes) and a shorter for darker.

The way to think about this is to realize you are roasting both the surface and the center of the beans. If you have access to an Agtron, you can see that once it's ground, coffee tends to be 5 to 15 points lighter than whole bean, since the bean centers are lighter than the surface.

The bean temperature you measure reflects how roasted the outers surface is, whereas the length of roast gives you some idea how closely the inside will match the outside. The longer the roast, the less the difference.

In a very dark roast, to a rolling second crack or beyond; there is a lot to be said for keeping the inside the bean a lot lighter by roasting fast. This will preserve acidity, sugars, and caramels to counteract the distillates, and keep the taste lively. Since the roast is dark, even the much lighter bean insides will not be under-roasted.

In a light roast, the last thing you want is the inside of the bean to be less roasted than the outside, since that means it'll be under-roasted, and the cup will taste grassy. On the other hand, you don't want to bake the beans to death by going very slow just before the first crack. Therefore, the best technique for lighter roasts is to go slow around 300F, so the beans' inside and outside are close to an even temperature as you jump into the roasting proper. This way the insides will finish properly in a reasonably fast light roast.

In cupping roasts, the finish is quick, around 90 seconds to 2 minutes from the start of the first crack, and there's a 5 agtron difference between the whole beans and ground. This gives an edgy taste, but leaves all the flaws exposed. A light roast for enjoyment can be just as light, but should run thirty seconds to a minute longer after the first crack, so that the bean centers can catch up.

#10: Post by **Hamilton** » March 30th, 2010, 4:34 pm

another_jim wrote:I prefer roasting by smell. There is a very distinct aroma change as the beans dry and start to roast, going the smell of boiling peas to that of bread beginning to bake. You want this to occur in the 300F to 320F (150C to 160C) bean temperature range. If it happens later, and you still get peasy smells at 320F, you need to start the roast more slowly. If the peasy smells stop before you reach 300F, you should start more quickly.

Jim,

Are there problems in the cup, or later in the roast that would indicate either one of these problems (too fast or too slow a drying phase)? I usually roast visually, and I have not really developed a nose for the changes during the roast. I have a terrible sense of smell to begin with, anyway.