An off-duty NYPD detective was punched in the head as she tried to stop an unhinged man from throwing food around a Midtown Starbucks Friday morning, cops and sources said. 

The 39-year-old female detective attempted to step in when she spotted the man hurling food items around the coffee chain’s Sixth Avenue and West 57th Street location around 7:45 a.m., authorities and sources said. 

The assailant then slugged her in the head, leaving a minor cut for which she was treated at the scene, cops said. 

Cops confirmed a person of interest was taken into custody after the burst of violence, but charges had not been filed by the early evening. 

The attack comes just days after a maniac bit a Bronx Family Dollar worker who tried to stop him from shoplifting – and then slashed another employee during a violent heist on Monday, cops said.

And in June, a brute who had been trying to steal a can of soda stabbed a security guard who confronted him at the Duane Reade on Third Avenue near East 52nd Street, cops said at the time.