They say not to re-freeze something after it has been frozen then thawed.
why?
It depends on how it was thawed. The USDA/FSIS site and many other reliable sources state it is perfectly safe to refreeze meat if it has been fully thawed in the refrigerator.
Even though it is safe to refreeze meat that has been thawed this way, many sources will recommend not doing so. After your thaw meat, and refreeze it the ice crystals that are formed expand and may puncture the cell walls. When the meat is thawed out again, these damaged cell will cause the meat to loose a lot of moisture. I have thawed and refroze meat, and I have not noticed a striking loss in moisture, but I like my meat medium rare, so that may be the reason I haven't noticed.
Cool. The meat in question here is for Jerky - so dry is _not_ a problem.
I vac seal most of my meat before freezing. I will sometimes thaw, change my mind, then re-freeze without any side effects so far. I have only done this with chicken and beef. I like my beef medium and my wife likes it well done, and we have not noticed any extra dryness.
Chicken is not as critical. It can be refrozen without losing quality as long as the pith of the bone has not reached room temperature.
Haberno Smoker has explained what occurs when beef and pork are refrozen. But keep in mind this refers to only refreezing without any further processing of the meat. In other words, there is nothing wrong with thawing a pork butt, making sausage and then freezing this product. You've further processed the meat. There is no quality change noticeable, and I may venture to say it is a common practice to the meat industry and home practitioner alike.
That's good to hear. Last Friday I put some frozen round steak in the fridge to thaw. I was going to make some jerky with it. I got so busy with other stuff it went back in the freezer today. Maybe next weekend. I haven't made that kind of jerky for ever!