final bean temperature

[beanless]

Hi there

I have read about the temperatures and the times for roasting posted by Sebastian for microbial kill rates but is that just related to the surface temperature of the bean? The reason I ask is that I am using a drum roaster and not the static 2" depth that Sebastian talks about in his post, so I am wondering if there is a bean temperature (and time held at this temp) that I should be aiming for.

Sebastian - hopefully you may offer some wisdom.

Cheers
Ali

[jdub9]

Good question Ali, I can't believe it fell on deaf ears.
Have you found an answer yet; I'm curious in knowing.
Thanks, Jim

[Sebastian]

Just to be clear, I have an extraordinarily demanding full time job, and it often requires that I travel, sometimes for months at a time, and not always to places that have internet access. As much as i enjoy the topic, and helping others, there's a very high likelihood that I'll miss any given message. I do make every attempt to provide non-confidential help where I can; however it's not always possible.

That said, I've already given the answer. It's whatever provides a 5 log kill. What - exactly - are the conditions that will allow you to achieve that? Well, you'll have to do some legwork yourself to identify that. I have no idea what equipment you're using, what it's made out of, how you're heating, what size it is, etc. It's impossible for me to give you specifics w/o having any of the specifics myself, and even if i did, there's so many possible combinations, the only way to answer it is to conduct the test. Asking for specifics is a bit like telephoning your doctor when you're not feeling well, and asking him for a very accurate diagnosis - he can provide some direction, but without doing some testing, he's only going to speak in generalities.

Likely not the answer you're looking for, I know, but it's the honest one. Additionally, surface bean temperature can lead to very misleading conclusions, as microbes are quite often found in internal bean structures as well - i would not use surface temp as your guideline...

If you have a local college, you may contact their micro department and offer a 'case study' opportunity for the students to solve a real-world problem, at no cost to you. Offering chocolates to the professor might help 8)

[beanless]

We couldn’t agree more Sebastion, whilst we were after an easy answer the more papers etc that we read which highlighted the dangers associated with bean micro spoilage contamination the more we realised that it is not a simple equation and we came to the same realisation. To achieve the log kill rates required is complex and involves what type of roast we were doing the bed depth and mixing whether we were utilising steam to assist and also what sort of temperature profile was being utilised as well as the residency above micro temperature thresholds to achieve the log 5-6 reduction that we are looking for. Your idea around trying to utilise a local collage to help with identifying how our particular process works is an excellent idea and something that we will be following up on. Thanks for your time, energy and commitment Sebastian much appreciated.

[Sebastian]

good luck ali - i think we talked via phone the last time i was in NZ? southern island, western side if i recall?

[beanless]

Thanks Sebastian, yes we didn't quite manage to catch up but if you are ever back this way with a spare moment let me know.