Salmonella can ride water into tomatoes (AP)

AP - Pick a tomato in the blazing sun and plunge it straight into cold water. If that happened on the way to market, it might be contaminated. Too big of a temperature difference can make a tomato literally suck water inside the fruit through the scar where its stem used to be. If salmonella happens to be lurking on the skin, that's one way it can penetrate and, if the tomato isn't eaten right away, have time to multiply.