Post-harvest processing for reduction of bean bitterness

Hi all,

I am looking to amass as much detailed information on post-harvest/fermentation techniques as I can get my hands on. I am particularly interested in any stages of the process that might be used to reduce bitterness in the processed beans.

I am currently sourcing my beans from a grower in Sarawak, Malaysia. He grows a range of high yield genetic strains in his sun plantation (over 10 types from places all over the world including Ghana and Brazil). He harvests pods on day 1 of his cycle, splits pods on day 2 and leaves in baskets, he begins a 3 box fermentation on day 3 (shifting beans from box to box after 40 and 80 hours). He halts fermentation at 120 hours, briefly washes in a  bucket and then sun dries over 3-4 days if the weather is good.

Would more frequent aeration in the later stages of fermentation reduce bitterness? Would a longer period of pre-drying before fermentation be useful? More pod storage? Better insulation of fermentation boxes to reach higher peak temperatures? Should the microbial fauna be kickstarted with additions i.e. sourdough starter etc?

I have read some vague descriptions of an interesting bag fermentation process being used by the Camino Verde farm in Ecuador. The sources imply that it yields very good flavour results from basic high yield varieties. Does anyone know the details of this approach?

Any assistance at all with these questions would be greatly appreciated!

Best regards

Matt

Bitterness can be coming in from many, many reasons - i'm afraid there's no quick and easy answer to your question that one can answer briefly on a forum.  I suspect it's a combination of genetics, pod age (maturity), fermentation protocol (too short), and how he's drying.  washing the beans is likely providing no material benefit.

Remember you can influence bean flavor by processing on YOUR end as well.  Roast time/temp/grind conditions/formula all are part of the equation.

Thanks, Sebastian, I appreciate your comments.

What roast time/temp would you recommend as a ball park for lower end forestero type beans? Long and relatively low temp?

I am working to improve things at my end I promise, but my grower is very receptive to feedback and often complains that the Malaysian Cocoa Board offer him little guidance on best current practice. Having heard comments out of Camino Verde along the lines of 'there is no such thing as a bad variety, just inadequate /unsuitable fermentation' makes me wonder as to possible adjustments on the farm end too.

That, my friend, is probably a 2 week long discussion involving a great many details.  The old adage of 'believe none of what you hear and half of what you see' probably applies here.

Anything you can give me to point me in the right direction?

I'm not aware of any publicly published comprehensive information sets on this.  This is a specialized area, where knowledge is developed over decades and typically held as trade secrets.

I have to disagree to some extent with what Vicente says, especially given that he is in Ecuador: very few people would agree that CCN-51 is a not bad variety from a flavor perspective.

Given what we now know about fermentation - the inoculated ferments that Camino Verde uses, as well as the guided wild ferments that Ingemann in Nicaragua uses - there is such a thing as improper fermentation, whether over- or under. It is also important to recognize that drying plays a huge role in flavor development and less is know about the effects of drying than fermentation.

That said, I also have to say that not every bean deserves to stand alone in a single-bean chocolate ... and that could be a combination of variety and post-harvest processing along with an all-too-common lack of understanding among small makers who think they know what "good" cocoa is, and actually don't.

Thanks, Sebastian and Clay. I understand that it is a very expansive topic. I find the black-box nature of the process fascinating though and would like to learn more. I will have to get over to Ecuador at some point - maybe on one of Dandelion chocolate's farm visits. It seems a missed opportunity that the research on fermentation and drying that must be being done on a fairly large scale by the big buyers is not being disseminated more freely. Would this not result in better bean quality/yield/grower loyalty (i.e. not switching crops)?

Is there any good source of flavour characteristic information for the commonly cultivated varieties? The grower in Sarawak currently has a very mixed crop and is looking to plant out another 100 acres,. He is interested to know which varieties would deliver best flavour for smaller makers (who are prepared to pay more than the MCB).

I would say that most cocoa processors/farmers really don't understand the drivers of post harvest quality well at all - but often think they do.  The 'big buyers' as you say spend 10's of millions of dollars on this, and understand it very, very well - but because of the significant investment, don't make that information publicly available because, well, they've made a huge investment into something that gives them a competitive advantage.  It's like any other business.  With understanding the levers one can pull on post harvest control and their impact, there is a tremendous amount of flexibility that it generates.

But are the big buyers not generally purchasing dried beans? If so then the post harvest processing has already taken place on the farm for better or worse. If they are involving themselves at the level of the farm this must involve large scale farmer engagement and information dissemination and thus don't the best practice guidelines leak out? 

What do small-scale growers in more developed parts of the world, e.g. Hawaii, have to say about best practice for fermentation and drying? Are they more happy to share successes and failures?

Large processors are very often very well integrated throughout the supply chain. Hence part of the reason they're spending 10's of millions of dollars.  In many cases, the processing is occuring at 3rd party fermentation / drying centers, where there are information protection controls in place, as well as massive financial implications. I won't go into what those are, and i'm sure there's some info leakage to be sure.

Matt -

The vast majority of the fermentation that goes on in the world is not instrumented. People throw out five days and six days - such as "if you go from five days to six days you will get 'better' results - as if they know what they mean. But, you cannot control what you do not measure.

What they don't know, or seem to care to learn or understand, is how variables such as water and sugar content of the pulp, pH of the pulp and the cotyledons (this is a significant marker), and which specific species of yeasts and bacteria are doing the work - affect the chemistry of the beans.

It's not just five versus six days, it's also understanding when the turns are made and how many there should be. Good examples are the Ingemann double- and triple-turned Chunos. Same length of fermentation, the major difference is in the number of turns.

It also depends on what you're looking for in terms of flavor. Longer fermentations tend to result in greater presence of chemicals that contribute to cocoa/chocolate flavor. Shorter fermentations tend to result in the presence of chemicals that contribute to more complex flavors ... but fail and 80% well-fermented cut test, so people write them off as under-fermented.

The first step in getting a handle on things is to instrument and document from the point of collection. Then you can get an understanding of how changes affect flavor and correlate them back to something concrete.