Cut the tuna into 1-inch cubes. Place cubes in the bowl of a food processor in batches and pulse until the consistency of ground beef. (If you do not have a food processor, chop the tuna into very small pieces.)  Place the tuna in a bowl and add the cloves of garlic, ginger, soy sauce, scallions, salt, and white pepper.  Using your fingers, rake all the ingredients together until combined.  Shape the tuna mixture into 4 patties using BurgerMate.  Refrigerate in a Ziploc storage bag or container until ready to grill.  Peel and slice the pineapple into 1/2-inch slices and grill on both sides for 2 minutes. Set aside.  Grill the patties over a medium fire, 3 minutes per side for rare, or 6 minutes per side for well done. Choose your favorite hamburger buns and lightly grill, if desired. Place the grilled tuna patty on the bun and top with a slice of grilled pineapple. Add your favorite hamburger fixings.