Bean to bar bitterness / astringency problem

Hey guys

I'm having an issue with my last few batches of bean-to-bar, made in a small 1.5kg Premier grinder. I had an issue with one batch of beans that produced a very intense bitter/astringent taste in the chocolate. I'm fairly sure this came from a bad batch of beans, although I didn't notice anything after roasting, so maybe just some of the beans in the batch were affected.

My issue now is that subsequent batches made from entirely different bean sources also have this bitterness, although to a lesser extent. Has anyone ever encoutnered an issue like this before, where a strong flavour can carry over to a different batch, even after thoroughly cleaning the grinder?

Alternatively, could it be an issue with the grinder itself? Perhaps grinding stone into the chocolate? I'm at a bit of a loss at the moment as the grinder does seem to be the only common factor between batches and I am (as far as I can tell) cleaning it thoroughly between each use.

It is almost certainly the beans.  W/o knowing the specifics of your formula, process, and most importantly - how the beans were made - it's going to be difficult to determine exactly what's going on.  What do you know about the origin and processing of the cocoa beans themselves?

Not enough, clearly.

The bigger issue for me is that the astringency is occuring now in batches of beans that I know to be good and have made great chocolate from in the past.

Big ol' trap in that line of thinking mate - beans can be HUGELY variable.  Even in the same bag, much less the same lot.  Localized clustering/clumping issues can happen all the time.  How certain are you that you have a homogenous lot of material to work with?

Cocoa beans aren't like finding a company that sells a shirt that fits you, so you konw you're 'safe' buying that shirt because it'll consistently give you a perfect fit.  Big companies devote a tremendous amount of time and effort to trying to control consistency and develop statistically sound sampling methods to attempt to minimize intra lot problems - but since you can't test 100%, it's sort of the nature of the beast that you'll find issues.  The smaller your purchase, the harder that becomes as you don't have any level of control over sourcing, nor can you even be certain the beans in your bag are all from the same region, country, or even growing year.  Nature of the beast mate.

Thanks for the help, I am aware of that, however it's really not the problem here. This is a very distinctive, very unique flavour characteristic that is running across multuple batches from multiple, entirely different sources - some of whiich have made made both award winning chocolate but are now producing inedible chocolate from the same small bag.

My question isn't about the beans. It's about wheter anyone has experience of an issue with grinders (or other kit) affecting the flavour.

If you're using a stone grinder, because they're so terribly porous, it's almost impossible to clean them fully.  That could be y our issue.  I still suspect it's beans however.

If it was from the roasting stage,

You would likely have resolved it on subsequent batches.

As your roast profiles are likely to vary slightly each time if your just trying things out.

how long do you take to make a batch.

I take 3 days. the first two days the chocolate refines in the melanger. then the third day is left for conching this is where the final flavour develops and unwanted bitterness evaporates.

You can actually smell and taste the flavour changers and bitterness coming of the melanger. 

Good Morning @dom-ramsey,

I think I know what your problem is. Are you using beans from local farms? I've had the same problem before, and specially at this time of the year. If so, then your problem is that the beans are not completely dry yet. It took me quite some time to figure out my problem when it had happened to me. I had just the same problem, and got astringend and bitter chocolate even from suppliers that I had good experiances before. I finally figured it out by using beans that were bitter after months of having them just sitting on a drying rack not paying attention to them. And then they made perfectly fine chocolate. 

It is sort of like with Walnuts. If not completely dry=bitter!!!

Let me know if I'm right