I received the following email from a ChocolateLife member, who gave me permission to post it here:
I’m starting up a group of farmers in the north of Malawi, right next to Matema/Kyela in Tanzania.
We’re getting beans from Tanzania that us giving a off flavour reminiscent of grass or a yeasty taste (not smell). The flavor is particularly pronounced in the cacao powder after roasting at 135° C for 20 minutes in a drum roaster. I’m grinding the beans as for chocolate liqueur, and pressing using a vehicle hydraulic jack and large truck cylinder.
- Is this possible to remedy through roasting and conching?
- Where do I start looking for the problem in the fermentation process?
The group we started only produce about 250kg of beans per week, but we’d like to build up a artisanal chocolate business aimed at tourism, if we can get the quality right.
To the best of my knowledge you may be able to process out the grassy notes in the chocolate by roasting and conching but you’d do that at the risk of processing out flavors and aromas you want to keep.
However – there may be a simple solution and it requires an answer to a simple question: How long is it from the time the beans come off the drying pad before they are roasted?
Believe it or not, “fresh” beans need to be aged before they can be used. There’s not a whole lot of formal research on this because it’s not an issue for most chocolate makers as it normally takes several months for the beans to reach the factory after leaving the farm. If you are roasting the beans within 8-12 weeks of their being removed from the drying pad there is a likelihood that you’ll get the notes you’re finding, along with yeasty and/or wet cardboard flavors.
I know that it costs to keep beans in inventory before using them, but I would cast about for beans that have been aged for at least 2-3 months before processing them to see if you have the same issues with aged beans.
I think it’s great you’re looking into a small-scale business that incorporates tourism and please keep TheChocolateLife community apprised of your progress!
I am looking forward to learning more.
Hi Pierre – curious as to if you were ever able to try splitting a batch and roasting half under your normal conditions, and half at the elevated temperature noted earlier – and if that had any impact?
I know also Ingemann uses info about the pH of the cotyledon to help them understand the progress of fermentation.
Did a quick bit of math here. There's a few chemicals that can be causing you the issue. Try this and lets see if we can't narrow it down. next time you roast, split your bean quantity in half and roast 50% of them the way you normally do, and the other 50% raise the temperature to 132C for the same duration of the roast and report back?
Out of curiosity, how do you use the pH data you collect? I've got scads and scads and scads of it, tracked every which way. I never was able to find a compelling reason to use it, other than as an indicator of bean maturity, disease state, or rate of post drying de-acidification (which has more to do with the rate of moisture loss during drying than anything). Lots of people collect the pH data, i've yet to see a very good rationale for doing so (even though i did it for decades). How do you use it? Edit: actually it was pretty important in understanding the intra-bean transport mechanisms of flavor development during fermentation and drying, but as a day to day quality check – meh.
I would love to see a video of the modified melangeur with the ceramic balls, running. I also reached out to the Komet oil press manufacturer. You have the Komet D85-1G? What sorts of yields are you getting with it?
In my experience, the 100L mass makes achieving consistent results more difficult and this is exacerbated by the comparatively thin walls of the plastic fermentation vessels. Wooden fermentation boxes will keep the heat in better.
I also recommend getting a refractometer to measure sugar content of the pulp and on my trips to Nicaragua with Ingemann and the Academia de Cacao learned the value of knowing the pH of the pulp at T0.
Is the added yeast because you don't get a good start to fermentation without it? Do you wash the plastic barrels between uses? In wooden boxes yeasts and bacteria reside from previous ferments that can help. I would also take a look at how nighttime ambient temperatures affect the temperature of the ferment.If the difference is too great then it will be necessary to keep the fermentation vessels from cooling down.
Your roast is probably too low and might not really be long enough. Do you have a thermometer in the mass of beans or are the temps you're reporting the temperature inside the roaster itself? When you add the beans what happens to the temperature of the roaster? It will drop (quench) but how far? And how long does it take to return to the desired temperature (recovery)? A small roaster doesn't have a lot of thermal capacity so the added mass of beans can have a huge impact on times/temps.
From the roast profile, it may be that you're effectively drying the beans out but you may not actually be cooking them especially at the center. Until the water in the bean evaporates off evaporative cooling prevents heat from the roaster from penetrating the bean. A more effective roast may get rid of the grassiness you're tasting.
Sebastian – Most makers don't have experience with aging beans because by the time the beans arrive at the factory they have aged so it's not an issue. Once I learned of this and tasted the results I realized there was a common flavor element among many chocolates made at origin by small makers using beans just of the drying pad … and now I knew where it probably came from.
100l fermentation – in my opinion – is too small to have sufficient mass to obtain consistent results. I'd at least 2x the mass if you're able to.
Can you tell me more about the fermentation? You've got vented plastic drums, approximately 100l in capacity, and are turning the beans. How often do you turn them? How long is the total fermentation time?
Why do you drain the excess liquid off the beans? This essentially reduces the 'fuel' for fermentation – which can be ok if that's giving you the flavor profile you're looking for. Generally speaking, however, for fermentation you're going to want to have the freshest, highest potential fermentation material possible to work with. I'd encourage you to invest in a handheld refractometer, and ensure the brix if your pulp is no lower than 13 at T0 Fermentation.
I don't think you need to add the yeast – there's tons of wild yeast all around you, and mass will auto-inoculate. While I'm not sure what yeast you're using, i don't think it's fundamentally the source of your problem – but what could be happening is that by adding a large concentration of a particular yeast strain, it'll outcompete some of the other yeast – and even bacterial – strains, that are important for the many, many mechanisms that go on during fermentation – and that could be a part of what you're experiencing.
I've no experience with aging of beans resulting in lower grassy flavors- but that's not to say that it's not true, just that i don't have any experience in it, and have never observed it firsthand myself. Typically, grassiness is either a function of fermentation or drying protocols – how long does it take you to dry the beans, and do you take any analytical measurements to know when the beans are 'done' drying? If so, what's the reading? Edit: Are you saying it takes more than 7 days to dry the beans? If so, that might be part of your issue. Ideally you'll want about a 5 day dry time to get down to 6-8% H20. Any faster than that and you'll case harden the beans, leaving a high internal moisture that'll rot the bean from the inside. Longer than that, and you risk mold growth from the beans being wet but warm for long periods of time – and that can create bizarre flavors…
In my experience, regardless of where the grassiness is coming from – assuming we're both talking about the same thing when we say grassy – we might not be – it's usually pretty easy to roast it out. Increasing the time or the temperature are pretty effective ways of addressing grassiness, if you can't ID where in the process they're coming from in the first place. Just because i've never burned acacia wood – any chance that it's coming from the smoke of that wood? I've seen lots of really odd flavors come from folks trying to use the heat of various burning things to dry their cocoa.
Apparently, the material is derived (seedlings only) from Trinitario brought into Tanzania around 80 years ago by missionaries (this needs confirming). Similar plantations have, in the case of the adjoining plantations of Mababu, been given heirloom status. The plantations are around Lake Malawi (Nyasa), and is from 480m to.550m above MSL (Kathininda around 490m).
The fermentation setup:
I've opted for fermentation in new plastic injection-moulded drums, 100 liters in size. We burn holes, using a heated 6mm rod, in the bottom and sides to allow good drainage. Drums are raised off the ground, on bricks, inside a storage room, and the process is checked by cutting beans every time we turn the batch.
Since noticing the off taste, I've made a few changes – we're now only going to harvest every second week, and the beans are first collected to drain excess juice on a mat of banana leaves before mixing and placing it in the drums (previously we scraped directly from the pods into a weighing bowl, and mixed in the bakers yeast as we filled up the drums).
Beans come from a mixed plantation, belonging to 18 individual growers. They harvest on a Monday, and live close enough to get the beans to the fermentation station within 30 minutes from cracking the pods – which can take up to two hours. We give each grower a clean 20 liter bucket with lid, and they bring the beans for weighing and inspection before inoculation and adding to the batch. After mixing, we start to fill drums to 80% of capacity. The dataloggers (2) are placed one in the centre, and one in the middle but along the wall of the drum. I only have two 64k loggers available at the moment.
I live 600km away, so traveling up every two months at this point, and staying in contact with the group through digital equipment and messages, pictures and instructions exchanged via email.
Any advice and discussion is most welcome.
The roasting is done in 5 kg batches in a hone made stainless steel drum roaster at present, over charcoal (700-800g charcoal/ batch, made of woodlot of acacia trees – Acacia xanthophloea
I roasted for 30 minutes, approximately, to get temperatures of around 110°C after 10 minutes, and maintaining this below 125°C for around 15-20minutes (total roasting time around 30minutes)
Nibs are separated after roller crushing, in a home built winnowerin, and size of particles reduced by passing through a Comet small oilpress (15kg/h maximum capacity). I then use 8mm ceramic balls in a modified CocoaTown melanger, to get the liqueur down to smooth consistency, taking about 6-8 hours.
The off flavour that I described as grassy, has decreased a lot already in the first batch on storage – subjective observation- and I suspect it is caused by hexanal and its derivatives. That could be explained by the bakers yeast inoculation? I suppose I get a more conrolled, but also a more aggressive fermentation in the first stage.
Beans are dried with good air circulation on reed mats, and stored in woven polyester bags (50kg) .
Let me know if I missed any other important information
Now that i know what to look for, it’s obvious. Could just be me 😎
Sebastian – I sent your note off to publisher support at the Maven, and I’ve asked what we can do to make new comments more visible.
Hi Pierre – this wasn’t immediately obvious to me (it could just be that as i’m aging technology is outpacing me…) – but my response is collapsed underneath your post, and may not be apparent that it’s there. In fact, when i came back to the page after i posted, i had to do a double take to find the post that i knew i just posted, but couldn’t find…
I need to drive on over and have lunch with Ed one of these days – it’s been too long since we’ve gotten together!
Hi Pierre – this is great – clearly you’ve done some of this before – it’s always a joy for me to ‘meet’ someone new who’s methodical and passionate about it!
I’m now going to ask lots of questions, the answers to which will probably create more questions for me to ask 😎
Do you know what varietal(s) you’re working with?
Do you know the elevation of the trees (highlands, or lowlands)?
Are you in control of the trees, or is the cocoa being brought to you?
If being brought to you, are they bringing pods or bags of beans?
If bags of beans, what are the bags made of, and is it the first time they’re being used? What was the temperature of the beans in the bags?
What was the brix of the pulp at the beginning of fermentation?
Do you have any photos of the bags, receiving area, pods, beans, fermentation area, drying area that you can share?
Where in the fermentation was the data logger placed (ie center of mass?)
Were the fermentation boxes vented (are there holes for fluids to drain out?)
Were the fermentation boxes ever used for anything else?
What were they stirred with? Was that thing ever used for anything else? Where is that thing stored?
How are the beans dried? On a slab? on a mat?
What is the drying surface made of?
Is it ever used to dry anything else?
Can air get to it from underneath?
Are you measuring the moisture of the beans as they’re drying/ at the end of drying?
If so, how? What’s your moisture curve look like?
Once dried, you store them in a plastic bin. Sealed or open? Was that bin ever used to store anything else?
I assume your grassy notes are in the liquor. How are you roasting/winnowing/grinding to make the liquor? Times, temps, methods, etc.
Great input. By grassiness, I refer to a “green” taste reminiscent of freshly mown lawn..the beans are processed very cleanly, no cross contamination, and were fermented for 7 days (low temperatures and rain in first couple of days required this) The fermentation was also – as en experiment – started off with inoculation with 10g packet of local bread yeast in a batch of 180kg of wet beans. Beans were fermented in 60 liter plastic bins, and stirred well every second day. On the 4 th day, temperatures reached 47°C (recorded with a HOBO datalogger), and when the temperatures kept dropping, the beans were first shade-dried fir 24 hrs from day 7, then moved to full sun. A nice dark reddish brown colour developed.
The beans were not showing any signs of mould or bacterial growth, and low acid smell compared to beans normally from groups in the region. After drying, and storing in plastic bin, acid smell (acetic) was more pronounced. A sample of 3kg (wet) was drawn at day 4.'
The grassy notes seems to be common to samples from the area this time of the year – of another 7 samples obtained, 6 showed the same “problem” – it does seem to decrease as the batch rests, and I will be keeping an eye on the process.
Ant other helpful suggestions, or comments?
I have to agree on your point that communicating about flavor is really tough to do – at a distance and even close at hand. I have no idea what Pierre means by grassiness.
The lack of research I was referring to was not about processing out grassiness but about the influence of aging on fresh beans. I had a long conversation with Ed Seguine about a year ago on this topic and his experience with some samples he’d been working with for Cocoa of Excellence. I offered up the observation as one point of entry to solving the issue.
Troubleshooting flavor from a distance is a VERY difficult thing to do, largely as a result of not having a shared lexicon (are you positive that what he means by grassy, you mean the same thing?)
There’s a tremendous amount of research in this area – almost none of which is public i’m afraid. Grassiness as a function of bean processing (note: NOT as a result of cross contamination), absolutely can be processed out. If it’s present as a result of cross contamination (ie be stored or coprocessed with other vegetal materials) – it becomes a bit more complex. Sometimes it can be processed out, sometimes it can’t.
Out of curiosity, what makes you recommend aging of the dry beans as a solution to grassiness?