A yummie is yours when:
• It collides with your barrier (NOT your shooter). Skill is required to fire a barrier that both intercepts yummies and clears a chunk of screen area.
• It is captured. This tactic is useful for grabbing a bunch of yummies flying around the screen at once. Just capture them in the area that is cleared with your shot and they're yours.
In both cases, you'll hear an "Ohhhh baby" sound when a yummie is nabbed.