Originally Posted by quince
...Do I need to add an acid whilst marinating? Or will that 'eat into' meat?
Whenever I marinate meat or fish, I try to avoid any acid. Like you said, it "eats" into the meat, or simply said; it cooks the meat without heat. Another thing I avoid is putting salt into the marinade. Salt draws moist out of the meat. Acid and salt make the meat tough, especially when marinating a longer time.
Try using only lemon zest in the marinade to get a nice lemony taste without the acidity. Be sure to remove all white from the lemon zest or the marinade will get bitter! A nice alternative is to grow a lemon verbena plant and add a handful of verbena leaves to the marinade; sensational!
And like FF, I marinate lamb shortly (maximum a few hours) and grill them as shortly as possible. I salt only when the meat is on the grill. I also use slices from the lamb leg (gigot). My marinade is simple; sunflower oil, thinly sliced garlic which will be removed before grilling, coarse black pepper, lemon zest, lemon verbena, rosemary. I always marinate the whole piece of meat first, preferably in a plastic bag. I cut the meat in smaller chunks after marinating, just before they go on the skewers.
Also a good idea when cooking lamb; after the meat is grilled, squeeze a little lemon juice over the skewers just before serving.