Sour chocolate

[fredrik]

Hi,

I have some issues with getting sour chocolate as an end product.

I roast in my home "hot air" oven. 5kg per batch on 4 perforated aluminium sheets. 125C for 35 minutes. Then I put it in the premier melanger and run 4kg batches for 72 hours. The end result is rich in flavor, but aftertaste is very sour. What can I do to keep the flavors, but get rid of the sourness?
 

[Chip]

It sounds like you have it down as far as the roasting goes. Are you getting good "popping and snapping" from the beans at this temp/time schedule?

72 hours in a melange is a long time imho.

The aftertaste could also be a result of the ratio of nibs/sugar/cocoa butter, etc. you are using. An 80% dark is going to have a lot more aftertaste than a 65% dark. What are your formulations?

[fredrik]

Thanks,

I'm not getting any noise from the beans at all. I have tried roasting longer (45 min) at 125C and also on higher temperatures (up to 140C), but have never got the beans to crack or make any noise. But I do notice that the taste is flatter when roasting a bit longer.

Do you think that the long time in the melanger creates the sour aftertaste? I need to go for that long to get the particle size down to 20-25 ym when running 4kg in the premier tilting melanger (10lbs size).

I'm using 70% cacao nibs and 30% cane sugar.

[Ben]

Where are the beans from? It could just be that they have a sour flavor to them. Running them in the stone grinder longer won't bring out a sour aftertaste. Generally, longer run times result in a more mellow flavor than otherwise as various flavor-producing chemicals have more opportunity to evaporate.

Oven time and temp are not particularly useful pieces of information. More helpful would be to know the end of roast bean temperature and the various times for the roast phases as Chocolate Alchemy describes in his series on roasting (see the Ask the Alchemist posts starting around #200 on the site).

On a side note, 72 hours doesn't seem particularly long for that much chocolate to me. I'd actually recommend running smaller batches, though. Once your chocolate goes over the axles in a stone grinder, the grinding and 'conching' efficiency goes way down.

[fredrik]

Hi,
the beans I am currently trying are:
- Haiti PISA
- Boliva Alto Beni

Do you have any experience, or knowledge about those?

I'm aware of the roast phases as described by Chocolate alchemy. The end roast is measured with IR temp to 125C, but I have no idea about the different stages. (on the wishlist is a drum roast…)

I'm aware of the batch size "issue" related to the stone grinder. But due to cost reasons (I cannot afford to buy bigger grinders) I have to run 4kg at the time. I run 72h to get down to the right particle size. My assumption is that the "conching" effect is anyway not significant in the premier grinder as it's not heated, or airiate the chocolate in any specific way.

[Ben]

I don't have any experience with those specific beans. Sorry. Have you experimented with different roast profiles? It could very well be that 125C is too high of a final bean temp, or that if you slow down or speed up the roast, that you could achieve a better flavor.

It is possible to chart the roast progression using an IR thermometer. Just crack the oven and take a reading every so often.

Regarding the batch size issue, I found that I was able to make more (and better) chocolate by running smaller batches as the time-per-pound of the smaller batches was less than the larger batches.

[Ben]

Another possible issue is the size of your roasts. How deep are the beans on your sheet pans? 5kg over 4 sheet pans sounds like it's probably deeper than a single layer. If so, they'll need to be stirred regularly to roast consistently. Otherwise, you're probably getting some less well-roasted beans that could very well be adding a sour flavor to your chocolate. I'd highly recommend roasting with only a single layer of beans.

Even with a single layer, I'd recommend rotating your pans in the oven to get a more consistent roast. Home ovens are notoriously inconsistent. When I was roasting on sheet pans, I would get a 20-30 difference between the hottest and coolest beans in a roast. I hacked a drum into my oven, which made my roasts much more consistent and controllable.

[fredrik]

Hi Ben,
1) It could very well be that 125C is too high of a final bean temp, or that if you slow down or speed up the roast, that you could achieve a better flavor.
- I am interested in knowing more about the background of this advise. Are you able to elaborate a bit more on the final bean temp, as well as the slower/faster roast. I do not fully understand what you mean.

2) Regarding the batch size issue, I found that I was able to make more (and better) chocolate by running smaller batches as the time-per-pound of the smaller batches was less than the larger batches.
- I have an idea that I will add 2,8kg cacao at the start, then wait 24 hours until I add 1,2kg sugar. That way the cacao would be airiated better and get a better "conche". Do you have any experience of dividing it like this?

3) Another possible issue is the size of your roasts. How deep are the beans on your sheet pans? 5kg over 4 sheet pans sounds like it's probably deeper than a single layer. If so, they'll need to be stirred regularly to roast consistently. Otherwise, you're probably getting some less well-roasted beans that could very well be adding a sour flavor to your chocolate. I'd highly recommend roasting with only a single layer of beans.
- I did just try to roast 1kg divided on 2 pans instead of 2,5kg divided on 4 pans (I wrote 5kg/batch by mistake in my first post). The roast was much more even and reduced the sour notes a lot. So I have ordered a new "commercial" convection oven to use instead of my "home" oven. Let's hope that helps.

[Ben]

1) For more info on this, see the Ask the Alchemist posts on chocolatealchemy.com related to roasting profiles. If I remember correctly, there are 5 or 6 of them starting right around #200 with a few more later in the series.

2) I've tested adding the sugar at different times and haven't found it to make a huge difference one way or the other. But I have found that grinding and conching efficiency go way down when you your chocolate is over your axles.

3) A commercial convection oven will definitely work better than a home oven, but my advice to have your beans only one layer deep still holds true. You may also want to look at perforated sheet pans which allow the air to move more freely around the beans.

[Sebastian]

Your sourness is coming from organic acids that were produced during fermentation. If your roast smells like vinegar - then the acids that are creating your sourness are acetic acid, and can be removed by roasting longer. If your roast doesn't smell like vinegar, then you've got a non-volatile organic acid (lactic acid) that will be present no matter how your roast your beans. There's a chance it can be processed out by incorporating sodium bircarbonate (baking soda) at a 1% level in your conche cycle. This may or may not work depending on any number of specifics that i won't go into here due to time.

[mark]

Hi Sebastian, always interesting to read your posts. Is my assumption / experience correct that the acetic acids also dissipate during refining with a melangeur?

[Chip]

Yes, that is correct.

[Sebastian]

Indeed - acetic is volatile - meaning it wants to evaporate. It's the reason you smell vinegar when you open the vinegar container - the acid is evaporating. When you melange, you're generating heat (which makes it easier for the acid to evaporate), and moving it all around - again making it easier for it to get out, in fact one of the large chocolate manufacturers places a probe over their conche to measure the concentration of acetic acid in the air as a control mechanism for their conching progression. At another manufacturer, there's a piece of speciality equipment that does many things - one of which strips much of the acetic out, and it's so strong that it's begun to destroy the equipment!.