what use it is given to the shell of the cocoa beans

Chris -

Thanks for the clarifications. There is history of infusing an already-produced rum or whiskey using cocoa. This is one of the things Cacao Prieto intended on doing and they purchased a huge macerating tanks exclusively for this purpose. They were planning to distill the resultant liquid, but my guess is that a simple filtration process prior to bottling is all that is necessary unless you suspect microbial contamination from the cocoa.

My experience is that it's more efficient to use nib (over whole beans with shell) because of the increased surface area available. Nib will absorb the alcohol much, much, faster than a whole bean can - and that's reason enough to go with nib. Another reason is that it's going to be easier to remove excess liquid from a mass of nib than it will be from a mass of whole cocoa bean and shell. (You do need to find something to do with the paste from the nib.)

If you want to try something in the kitchen, get an ISI cream whipper and NO2 cartridges. Warm the container with hot water and then empty - no need to dry. Measure in some alcohol (sweeter - relatively speaking - rums and bourbons give better results than less-sweet spirits such as vodkas and many whiskies in my experience; gins are mostly a no-go), and measure in some refreshed nib (warmed up in an oven). Pressurize the container and shake. Wait 3-5 minutes before carefully releasing the pressure. You will have cocoa-flavored spirits -- and you can control the level of cocoa flavor by experimenting with the ratio of nib/alcohol, type of alcohol, other ingredients, and time spent macerating under pressure.

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clay - http://www.thechocolatelife.com/clay/

Chris -

"[...] the temperatures involved in the distillation process, coupled with the alcohol of the finished product, are likely to kill any bacterial pathogens that might be present on the shell."

Does this still hold true now that I've clarified that the product would be a rum infused with cacao and not a spirit distilled from cacao? 

Temperature is only a consideration if you re-distill after maceration. Alcohol levels still apply.

Also, does this also hold true for the brewing of beer? Figured it's worth asking since the alcohol content is significantly lower.

It depends on how you get the cocoa flavor into the beer.

You could do it by making the cocoa nib a part of the mash bill (whole beans would probably not work). In which case, the boil would kill everything. However, there are issues with respect to fat content that need to be taken into consideration if you are going to boil nib. This is something that a competent brewer should know about.

If you are getting the flavor into the beer using the technique known as dry-hopping (again, whole beans will not work here), then you are relying totally on the alcohol to take care of any microbial contamination unless there is a post-winnow sterilization step. I don't know the efficacy of a 3.2% level of alcohol relative to an 8%+ level of alcohol. You'd have to test.

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clay - http://www.thechocolatelife.com/clay/

updated by @clay: 02/05/17 12:55:46

Clay: 

Thanks for all the info. That pressure-maceration trick sounds awesome, too, so I'll definitely try that sometime! Seems like main thing I'll have to contend with then in the scenarios I've described is heavy metal and other inorganic compounds in brewing. Fortunately, this brewery has a chemical engineer of-sorts on staff, so he'll probably be excited about testing for that. Cheers! 

I will add on tangent.

In the beer brewing world, roasted cocoa nibs are used as an flavour additive in several different beer recipes. Roasted to develop flavour and than soaked in neutral alcohol to sanitise. Introduction of live microorganisms present on nib into brewing systems brings very unpleasant results.  

Peter - Good tip as a way to perform the kill step after winnowing.

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clay - http://www.thechocolatelife.com/clay/