I defrost about 40g of meat a few times a day for my cat. I take the meat out of the freezer and put it into a small sealed container which sits in the refrigerator for a few hours.
Sometimes the meet has weird dark spots, but only on the inside of the bits:
What are those?
Is my technique of defrosting meat correct or am I doing something wrong?
You're not doing anything wrong. If you kept the meat fresh, in your fridge, eventually it would undergo color changes, as well. Freezing meat and then thawing it is also a pretty major set of physical changes to it's initial state. I'd think minor changes to its appearance would be expected.
Ask USDA: Why does the color of food change when frozen?
KNOWLEDGE ARTICLE
Color changes can occur in frozen foods but the foods remain safe to eat. The bright red color of meat as purchased usually turns dark or pale brown depending on its variety. This may be due to lack of oxygen, freezer burn or abnormally long storage. Freezing doesn't usually cause color changes in poultry. However, the bones and the meat near them can become dark. Bone darkening results when pigment seeps through the porous bones of young poultry into the surrounding tissues when the poultry meat is frozen and thawed. The dulling of color in frozen vegetables and cooked foods is usually the result of excessive drying due to improper packaging or over-lengthy storage.
