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We've noticed that different beans seems to have different amounts of intrinsic oil. The Peruvian Maranon seems to have quite a bit of oil and produces a chocolate that flows very easily but it tricky to temper correctly. Is there a way to know in advance the amount of oil in a bean so we can adjust the amount of cocoa butter we add?
Yes, cocoa beans have different levels of cocoa butter. There isn’t a practical way to measure the amount of cocoa butter yourself. I’ve tried multiple times and the results don't reproduce well which in turn makes the data basically useless.
I tried to determine the amount of cocoa butter at home using techniques readily available coupled with my knowledge of laboratory procedures so I could pass it along to you. It didn't go well.
The general procedure is to grind up the beans into liquor, mix it with a solvent that will dissolve the cocoa butter and allow you to separate the solids and then weigh and calculate the amount of oil in the solvent. Unfortunately the only solvents that cocoa butter is freely soluble in are ether and chloroform and somewhat soluble in various hydrocarbons like hexane. None are available to the general public since they are dangerous without proper protective gear and equipment. Cocoa butter is also soluble in dehydrated alcohol but again that isn’t available to the public nor is it easy to produce at home. Even Everclear at 190 proof has too much water to work well. But since that is as close as I could get, I decided to give it a try.
In short I failed miserably. The water just caused too much of a mess. The mixture just formed an emulsion. You can read this as mud for the amount of liquor I needed to use so that I could get a extract enough cocoa butter to weigh on the gram scale I have.
By using a lot of Everclear, and a bunch of salt get the cocoa solids to settle out I ended up with a jar of yellow liquid presumably colored by the cocoa butter. Boiling off the ethanol directly didn’t work well at all. At some point it hit a gummy thick stage that would not turn into pure cocoa butter and which weighted more than the amount I started with. Clearly it had too much water in it still. Start with 10 grams, end up with 15 grams....nope.
I eventually slowly dried it over days letting the ethanol and water naturally evaporate. It was very slow. I ended up with what looked like pure cocoa butter in my jars. I was very hopeful until I weighted them and calculated the cocoa butter percentage. My three attempts were
Like I said, a miserable failure since we already know there is 50-55% cocoa butter. Days and days of work that was not any good. The water and non-laboratory conditions were just not suitable.
For those extra daring, in theory you could try gasoline since it is a hydrocarbon (it contains hexane) but I would not advise it for two reasons.
1) You have to evaporate all the gasoline and that just isn’t healthy
2) It is only slightly better for dissolving cocoa butter and would probably give you similarly poor results.
You can of course have the beans analyzed in a laboratory. I have personally done it. I didn’t just have them analyzed but literally did the analysis myself and I can tell you cocoa beans are a hard matrix to analyze. My results were better than those I was able to perform at home, but they still were not very useful. The problem comes in with your need for a very precise and accurate number and what is considered acceptable from a quality assurance standpoint in the laboratory.
I used the proper solvents, evaporation techniques and equipment and on a set of 5 samples I was able to produce these results.
From a laboratory quality control standpoint this was not too bad. It gave a relative standard deviation of 8.1%, a standard deviation of 4.3% with an average of 53.4%. This officially passed the laboratory quality control limits and could reported to the customer, usually without the supporting data. Only 53.4% would be given unless other data was asked for. So keep that in mind should you have samples analyzed. You may get a single number and believe it to be the truth but it isn’t the whole truth as there are a bunch of statistics and uncertainty in the data.
A common way to phrase it (and yes, it can sound like double speak and dodging the answer) is that I was 96% certain that the actually percentage was 53.4% give or take 4.3% (the standard deviation). Or I am 96% sure the answer is 49.1 - 57.7%.
Are you noticing a problem?
At the end of the day it is just way easier to refine your chocolate and then add a little more cocoa butter right at the end until you get the thickness, or lack thereof that you desire.
I want to bring up one other observation that I have had recently with all of the vertical EOR roasting profile tests I have been doing.
I can say with confidence that final viscosity is affected by your EOR temperature the higher temperatures leading to consistently thinner/less viscous chocolates. 234 can be on the thicker side, 248-250 pretty average and 260 and over flows like melted butter.
There are some other loose correlations I saw also but they are much less well defined and harder to separate from the final EOR. Longer roasts seem to be slightly less viscous, as do REALLY long drying phase roasts (as in over 20 minutes). Mostly I toss this information out there so you keep in mind that it may or may not be a the cocoa butter content of your cocoa beans causing viscosity issues. There are clearly other factors that come into play.