These cubes were made from myoglobin that was left over from my beef kidney prep. It’s a liquid substance that seeps out of the meat you’re prepping. There was so much of it that I decided to freeze it into cubes and add to my dog’s meals. “The red liquid, instead, is a mixture of water and a protein called myoglobin (not blood), whose purpose is to help ship oxygen to muscle cells. Myoglobin is deeply pigmented, which is why the more myoglobin a meat contains, the darker (or