Understanding beef grain ∞
- Muscle is long lengths of fiber.
- Imagine a series of straws parallel across your desk.
- Cutting "along the grain" is like separating several whole straws from the group.
- Imagine chewing that bundle of straws.
- It is "chewy" in every direction because your teeth are separating out individual straws and ultimately working hard to slice straws down into smaller pieces.
- Cutting "against the grain" is like slicing the tips off of the ends of your desk of straws.
- Imagine chewing on a row of those straw-tips.
It is "tender" because your teeth can easily separate that bundle of tips into pieces.
So the resulting grain length is what determines how tough or tender your cut is.
When cutting against the grain and you cut on an angle, you are "cutting on the bias", which makes it even more tender. This is useful when you have a rather unusual/curving grain you are cutting against.
Unless you want to make beef jerky particularly chewy, I don't know of any case where you would want to have long, tough, strands of beef.