Just found some nice raw meat 3D models:
https://p3dm.ru/files/others/props/12288-meat.html
They come with their hooks, so they are perfect for swinging from the U-boat roof, though, according to
uboat.net, fresh meat was stored inside a little refrigerator in the galley, thence it wouldn't have been visible elsewhere on the boat.
They are low poly too, so they can be used as cargo of some reefer model (spawned by damage).