I'm not sure if the brine time was long enough, and I'm not sure why you want to hold it longer than a day or so.
Here is the deal.... beef can be corned with a brine (also called a pickle), or it can be dry cured. I have not seen a double cure (or aging) like you are doing. If you opt for the immersion brine method like you are using, the brine time is based upon the thickness of the meat (so a London broil will corn faster than a rump roast, or a flat will corn faster than a point). Based on the concentration of your brine and your meat thickness, you arrive at proper brine time to corn the beef. If you opt to inject and immerse the beef in a brine, your brine time is cut way back. Commercial producers use the brine/inject method on corned beefs and hams.
For the most part, folks develop various strength solutions for various purposes, (turkeys, corning, making bacon etc.) and once they find one that works you are good to go. There are tables which measure brine strength in degrees, and you use a salometer or brine-o-meter to measure your solution. These are fun to play with, but again once you find something you like you just use that recipe. The floating potato or the floating egg is pretty unreliable because neither one is constant.
As far as the seasoning following corning, I use a similar one to yours and I let the seasoned beef go at least overnight in the fridge. Much longer and my black pepper and coriander gets soggy.
So, back to your question about holding time. Are you following a particular recipe or method? And did the folks at the German market give you any recommendations on how to mix the brine and how long to brine based on thickness?
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