Turtles are aquatic animals. They eat underwater. Therefore, anything that lives in water is potentially part of their diet.
The frozen foods are basically red meat scraps, packaged up and labelled as turtle food. However, just because the label says 'turtle food' does not make it suitable for turtles.
Write to the manufacturers of these products and ask them for a copy of the scientific studies that prove their products are suitable for Australian turtles. You won't get a reply.
In fact, the studies actually show that red meat is bad for Australian turtles. Not surprising, given that turtles feed underwater and in Australia, red meat animals don't live underwater. Therefore, red meat is not part of a turtle's 'natural' diet.
Turtle kidneys are different to human kidneys. Turtle kidneys cannot process salt or the fat in red meat. If you continue to feed seafood or red meat to an Australian freshwater turtle, eventually the kidneys will fail and the turtle will die.
Stick with foods that the turtle would find in its natural environment. Freshwater fish, freshwater yabbies, freshwater prawns, freshwater mussels, freshwater snails, tadpoles and (for short necks) freshwater plants are all food that the turtle may naturally feed on.
Many people get confused in regards to turtle diet. Just because a turtle eats the food you give it does not mean that it is healthy or suitable for them. Yes, if you offered red meat to a turtle, it will probably eat it. But then again, if you feed onion to a dog, it will eat it. If you offer a child chocolate for breakfast, he or she will eat it. I've even known Aussie blokes to drink beer for breakfast. But, eating a food or drink does not automatically make it healthy or suitable.
We humans can normally tell nutritious foods from non-nutritious food. Turtles cannot. So, if you are keeping turtles, it is your responsibility to feed them a suitable diet.
Regards,
Michael.