and stored as binary data in a BLOB field using UTF-8 encoding.

UTF-8 encoding is for text data. Binary data doesn't need an extra encoding.

Do I need to read the binary data into a temporary file first with a suitable encoding option and then pass this file to the Parse() method?

No, all encoding steps that an IO layer might perform can also be done without writing to a file (for example with Encode). But you shouldn't need this, because you should never treat binary data as text, and never encode or decoded it with utf-8.