HELP! What's happening to my beans?

There seems to be a massive misconception between tipping, scorching, blowing, and burning.. Part of the problem is there is no naming convention – does “roaster” make reference to the individual or the device; is “dropping” taking the beans out or putting them into the drum? Is “tipping” and “scorching” a similar thing and how can we spot the difference?coffee roasting business 

Well, I don't know who decides on the precise naming conventions, but here's my undertake it:

Tipping
The term “tipping” most likely identifies the phenomenon where in fact the “tip” of the bean burns black. That produces sense in my experience, at least.

How to “spot” Tipping

Tipping happens when the beans experience any temperature too much for the bean's heat-transfer coefficient. i.e., there is so much energy (heat) around a certain area of the bean that the bean cannot absorb/conduct/disperse the power fast enough. The only choice left would be to burn because area.

An analogy can be found in virtually any form of meat grilling. A straightforward lamb chop on the grill has tipping across the edges. This is caused by an excessive amount of heat at any one time, causing the meat to char in place of cook. This is exactly what happens to the beans: there is an excessive amount of heat for the bean to occupy, therefore it burns.

What causes Tipping?

So, when does tipping occur? The fact is that people don't know exactly. The definition above tells us so it could happen whenever you want, whenever the temperature is too much through the roast. It could happen due to too much a receiving temperature (the starting temp), too much a slam during roasting…an excessive amount of heat anywhere!

The following question is whether this is caused by convection or conduction heat? Quite simply: is the drum too hot or is the air too hot? The clear answer is: either. Tipping is really a factor of the beans, not the environment, the roaster, the drum, or air temperature. The fact is that the beans cannot handle it.

Look at the image below:

Tipping
Photo Source: www.sciencedirect.com

The colours show the difference in temperatures inside the beans. It's clear from the image that, if anything should burn, it will be the tips of the beans! But this changes depending on the bean: try finding tipping on peaberries. Because the peaberries are round and has minimal distinct “tip”, the chances of tipping happening are much smaller in peaberries.

What is the effect of Tipping you roast?

So, is tipping a poor thing? That is a question only the drinker can answer. Allow me, as I cannot stress this enough:

TASTE YOUR COFFEE!

Quite simply, if the coffee tastes bad, then tipping is bad. If your coffee tastes good but you have tipping, then surely tipping is not a bad thing! May be the “tipping” on the lamb chops a poor thing? No, we all love only a little char-grilling on our chops. But surely this is per definition a burned chop? Well, possibly so, but it still tastes great!  The chances of tipping affecting your roast to the stage of experiencing to dump everything is extremely slim.  Chances are that the chosen profile or roast degree is way off, and that tipping is just a very small area of the problem.

Scorching
So, if tipping is really a burnt spot on the end of a bean, then what's scorching? In my experience, scorching is bad practice. Certainly not a poor tasting bad practice, but one which points to inexperience quietly of the roast master.

Scorching happens when the bean touches a floor that's too hot for the thermal conductivity of the bean. Just like for tipping, but almost exclusively caused by conduction heat. In layman's terms: your drum was too hot! Try a cooler charge temperature or reduce steadily the ramp-time of your profile to negate any scorching. You should not need certainly to scorch the beans to attain your preferred roasting profile.

Scorching is different from tipping in so it typically presents on the flat side of the bean. It is really a larger spot that's burnt black.

Some tips about what scorching looks like:

Scorching
Photo Source: www.perfectdailygrind.com

Cratering
There will be a lot of confusion between craters and tipping. The two are VERY far apart. Cratering happens near or into second crack where in fact the pressure inside the beans is released at such a higher level that the bean's surface cannot handle the release. This is per definition “second crack”, but in the case of cratering, the second crack was brought on so much so it affects the structural integrity of the bean and literally blows a bit off when the bean releases the built-up gasses inside the bean.

Crating
Photo Source: www.fullcoffeeroast.com

What is the perfect solution is?
If you select that tipping, scorching, or cratering is the cause of any unwanted flavours in your bean, here's how to proceed:

Tipping: Lower your charge temp and do a slower, gentler roast.  Increasing your convection heat also needs to help, as well as increasing the batch size and drum speed.  The best should be to roast longer and gentler to allow your beans enough time and energy to absorb and distribute the power that you want to force into them.

Scorching: Lower your charge temp and raise your drum speed.  The less time the bean spends quietly of the drum, the less scorching you will have. Try to maximise your convection heat and minimize your conduction heat, i.e., transfer your time by way of heat in place of a warm drum.

Cratering: Increase the time from first to second crack and take a gentler approach will assist you to prevent cratering.  Dial back on your gas pressure when you reach first crack and let the beans carry themselves into second crack.   In the event that you force more and more energy into the batch, it stands to reason that “something's gotta give&rdquo ;.In cases like this, the whole bean is splintering apart because of your requirement for burnt coffee!

The Genio Academy, together with Shaun Aupiais from We Roast Coffee produced a brand-new online Coffee Roasting 101 course on our Genio Hub, available to any or all Genio customers, where he discusses common roasting defects in depth. Click on the link to view this type of module.