How to prevent beef muscle meat losing water during storage in the refridgerator?
You can't prevent it, that's how it works. It will always lose some liquid, no matter what. This is why supermarkets sell packaged meat with &quot;diapers&quot; on the bottom.
As mentioned in comments, you can buy dry aged beef. It has already lost that moisture, so you won't have the liquid to deal with, if that bothers you. This doesn't mean, of course, that you will somehow &quot;save&quot; the liquid, it will still have flown out.
Another theoretical option is to buy better quality meat. Mass-produced meat from young animals who don't exercise tends to lose more moisture than the meat from traditionally raised animals, especially if you are looking not at tenderloin but at stewing meat from old cows. I am including this information here more for completeness' sake. If you find a supplier for this type of meat (which is difficult in itself), you will save part of your 5% weight loss, but you will pay 4-5 times more per kg, if not more, so it doesn't give you an economic advantage.