She sewed chaos among local police after several people found the sharp objects in packets of mince meat and steaks bought from Lidl supermarkets in Eutin and Malente, near Lübeck, Schleswig-Holstein.
Police said they had identified 20 cases dating back to October 2013 where the needles had been put in the meat.
One woman scratched her hand when she was preparing mince and a 17-year-old noticed another needle in her mouth but took it out before it caused her any harm.
The 60-year-old woman from the area has come forward to admit to carrying out the crimes, police said on Sunday following an appeal on Saturday.
As yet, police have been unable to unravel her motives for the crime.
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