What exactly does the -binary switch do when creating s/mime output?

Given: openssl smime -binary -sign -passin "pass:SomePassword" -signer cert.pem -inkey key.pem -in Document.txt -out Document.txt.sig -outform DER What *exactly* is done to the s/mime text to create a "binary" file? I'm trying to do the equivalent in Java using BouncyCastle and just can't get

What is the Java equivalent of "openssl smime binary" ?

I've created a prototype, in Java that creates an s/mime file, and now I need to convert that to the equivalent of what the "binary" switch does when using openssl. The command in openssl is: openssl smime -binary -sign -passin "pass:MyPassword" -signer cert.pem -inkey key.pem -in DocumentToSi