What specific structural requirement does the US standard sometimes impose on "preserves" that differs from the requirement for jam regarding fruit presence?

Answer

Requiring 50% of the weight to be attributable to identifiable fruit pieces.

While jam requires a certain percentage of fruit ingredients, the standard for preserves often emphasizes the structural quality, sometimes requiring that half the final weight consist of fruit pieces that are still visible and identifiable.

What specific structural requirement does the US standard sometimes impose on "preserves" that differs from the requirement for jam regarding fruit presence?
foodpreparationfruitpreservejam