I am doing a research paper for my science project. And I need to know how do oranges become contaminated?

Question

after it is refridgherated

Answer 1

Raw and minimally processed produce can occasionally become contaminated with disease-causing organisms such as Escherichia coli O157: H7, Salmonella, or Listeria monocytogenes. Since the number of illnesses associated with eating fruits and vegetables has increased, scientists and public health agencies want to be sure consumers know how best to keep their foods safe to eat. In addition to bacteria, produce can pick up dust and soil during harvesting, packaging, handling and shipping. Fresh fruits and vegetables may also have traces of chemicals on the surface. As much as fresh fruits and vegetables are healthy so do they present food safety challenges.

Answer 2

Two ways.
Systemic contamination happens when the contaminant enters the plant and travels to the orange.
Surface contamination is external and some times can be washed off.

Some contaminants land on the surface of the plant, get absorbed and then become systemic.
Some organisms produce toxins which get absorbed.