Rehydrating beans - any experience?

[nrdlnd]

I've had problems with irregularities in the ROR-curve in the developing phase with my test roasts. I recognize this problem from earlier roasts and it's probably because the PID overreacting because of all the physical and chemical reactions from the beans that affect the readings from the probe. I have tried a power zone and just now I have a negative (-1) power zone at the end with some success. The big irregularities are gone. I have also a positive boost zone before 1st crack. It's starting to look rather good.

[TheBean]

I roasted rehydrated Nicaragua AAA beans with KL 1200m - 1500m REST profile and RoR was very nice; just the first 50 seconds the actual roasting curve dipped under the profile but then nicely recovered and followed the profile till the end. The beans are resting now - can't wait to try them.

[Geronimo]

Gidday

Is the stock profile used for the Nicaragua AAA beans tweaked?

Cheers
G

[nrdlnd]

Very interesting @TheBean that it worked with the stock profile 12-1500 Rest! @Geronimo this profile is already "tweaked". It has two positive boost zones 1 and 2. I'm not surprised it worked in the first 2/3rd of the roast as the profiles I've tried haven't needed modifications in the beginning of the roast when when I've rehydrated the beans.

@TheBean how did you moisture the beans? Do you have a moisture meter? I have and the moisture differs between different stocks of beans. To my surprise the newer beans are often drier. Older beans that I've stored for some time seems to have more moisture. It seems that they adapt to my storing conditions. Newer beans that have been correctly dried have in my case a moisture around 10% or a little lower (but not all). Older beans have often a moisture around 11.5%. To make 100g beans with for example 15% moisture I add about 6g water to the drier 10% beans (94g beans and 6g water) and to the 11.5% I add 4g water to 96g beans. This is to get 100g rehydrated beans that is my usual batch. Of course it's not absolutely necessary to reduce the amount of beans before adding water as the water will evaporate during the roast. I have as the profile I have been using is rather power hungry and I don't want to "run out of gas".

If you don't have a meter you can always add some water but you can't get constant results as you don't know the moisture at the beginning. That's what I think but I may be wrong. It depends in what climate you live and how you store your beans what moisture they will have. Though I think it's safe to add for example 5g water to 95g beans 8-20 hours before the roast and see if you like the result. Maybe you will find it makes the roast better or if not forget it. I'm not ready yet with my evaluation. It had been very nice if more people contribute!

[Geronimo]

Hi

I agree that it would be nice if more people would contribute. It’s actually hard to believe with the number of KL machines out in the wild that there isn’t more posts. This rehydration topic is very interesting.

Im away from home, so no roasting for a while. When I do get back, I’m going to try adding a little bit of water and wing it somewhat, and see what happens. I’ve got limited power so think I’ll go a bit light on addition of water.

Cheers
G

[TheBean]

I don't have a moisture meter so had to try "blind" by adding 4g of water to 96g of beans and keeping them in closed glass jar for 9 hours. Roasted them on the same profile as non rehydrated beans. Today I tasted the beans: it had some minor change in flavour but not huge. Perhaps these beans are not the best for rehydration trial because they're large and heavy to start with and after adding some moisture they didn't move for a minute and a half at the begging of the roasting. The other concern is the rehydration method: adding a water might not be the same as addicting a moisture by placing the beans in a humid environment. It's an interesting subject... The most important part is to enjoy its product.

[Geronimo]

Hi TheBean

Have you tried ramping up your fan speed a bit to get adequate movement. Could try the manual no heat mode, as per the KL manual (screenshot included in this post), to see how you profile performs with respect to circulation.

Cheers
G

[nrdlnd]

@Geronimo very nice tip. I didn't know about the manual mode without heat. You can without risk ramp up the fan speed in the beginning of the roast as the roaster will not reach the max available power in the beginning or it doesn't matter much if it does. A too high fan speed at the beginning can limit the amount of heat that you want to give the beans in the beginning. Some hard and dense high altitude beans may need more heat in the start of the roast. When the beans become drier and lighter they move much easier and it isn't necessary with such a high fan speed to get the "fluid bed" working. A very high fan speed at the end of the roast may result that the machine can't follow the profile because of the higher power demand. You will need 240V for some profiles with a very high fan speed at the end of the roast. EDIT: My machine is made for 220V and I have 230V so I have more available power than 1400W.

[TheBean]

Instead of increasing the fan speed, I reduce beans from 100g to 80g and it does the job.

I tested rehydrated roasted beans on day 5 and the flavour developed into more sour-winy notes, quite different from non-rehydrated beans.

[nrdlnd]

I first want to say to @TheBean that according to the article linked to in the beginning of the thread it's important not to moisture the beans too long time to avoid mold. The article also says that the beans easily takes up the water but that more of this water is "free" in the beans but will help to enhance the roasting process.I have noticed that 1st crack comes earlier and that the end temperature is lower at a compareable roast degree. I think "L" with the KL is only defined by the end temperature so it's only arbitrary. So if the "L" says "Light" it's usually "Medium Light" or "City" depending what scale you are using or where you live. I have worked with a profile and after a lot of changes I think I've got it to work with beans rehydrated to about 15-16%. I want to make roasts on the light side and most often they become Light/Medium Light.
I started with Damians D-Light profile. It needed a little to much power for my roaster and my voltage because of the high fan speed. First i changed the fan profile. In the picture the weaker line above is the original D-Light fan profile. It's still a rather high fan speed.

Fanspeed_comparison.png (32.97 KiB) Viewed 5657 times

I then made other modifications mainly testing them with Grade 2 beans from Ethiopia. These beans are a little smaller but grown on a high altitude so they are hard and can take a lot of heat. I have made three zones: Zone 1 from 3:00 to 5:07 with a 3 boost. Zone 2 from 5:07 to 6:40 with a 2 boost. Zone 3 is a power zone from 6:40 to 10:00 that I after several tries ended with a 0 setting (same power after the start of the zone to the end). I may change that to -0.5 but haven't done it yet. This is the last roast I made with the profile with rehydrated Sidamo Wendo beans rehydrated from 10% to 15-16%. I put 6g water to 94g beans and let them soak for about 20 hours. (8 hours is said to be minimum). L became 1.1. "Light" says the KL but I think it's more Medium Light. ROR looks rather OK. End weight 82,8g.The end temperature was 215.6 degrees C. DTR 20%. EDIT 220125: I grinded the beans and tasted the brew today. The color of the grind shows that it's more on the light than on the medium light side. The beans haven't rested enough. It has a not unpleasant citrus acidity, some spiciness, clean taste but not much body, balanced and holds together when cooled down. I can't taste that it's baked. This bean is probably not very special but will see when it has got more rest.

220124_SidamoWendo_rehydr_DLightRPfanmod_1.1.png (71.66 KiB) Viewed 5657 times

220127: I have deleted the profile as it didn't work well with another bean and a tendency to ROR crash and too little power at the end of the roast. I will test again with a negative boost zone and let the PID do it's job.