Food safety recalls and salmonella outbreaks have become more common in recent years, but tainted produce may show up in some stores more than others.

Specifically, researchers say stores frequented by low-income shoppers are more likely to have produce that can make you sick.

Researchers compared levels of bacteria, yeast and mold on identical products sold in six Philadelphia-area neighborhoods. They selected three of the neighborhoods because they had the city's highest poverty levels. In these, consumer options tended to be small markets that offered less variety in fruits and vegetables.

The result: ready-to-eat salads and strawberries sold in stores in the poorer neighborhoods had significantly higher counts of microorganisms, yeasts and molds than the same products purchased elsewhere, while cucumbers had a higher yeast count and mold and watermelon contained more bacteria.

"Food deteriorates when there is microbial growth," said study co-author Jennifer Quinlan, a professor of nutrition and biology at Drexel University. "The bacterial count is used to determine the quality of the produce and it was poorer quality, closer to being spoiled. Three of the things that had a higher bacteria count - strawberries, ready-to-go salad and fresh-cut watermelon - have been associated with food-borne illnesses."

The study appears online and in the May issue of the American Journal of Preventive Medicine.

Why some don't eat more fruit and vegetables

When your access to produce is of inferior quality, it discourages you from adding more fruits and vegetables to your diet. Part of the problem, Quinlan said, is that much of the food available in poorer neighborhoods is for sale in smaller stores that might not have the infrastructure to handle produce in the safest way.

"The food may be of poorer quality to begin with; then it may be transported to the stores and not be refrigerated properly," she said. "Large supermarkets have entire units focused on food safety, refrigeration, sanitation. While a small facility with only one or two people may not have the resources."

Although the bacteria that can cause spoilage are not the same bacteria that are dangerous from a standpoint of food-borne illness, consumers can take some important steps to ensure they get the freshest produce.

"One thing consumers can look for is that fresh-cut produce be refrigerated at the point of sale," said Shelley Feist, executive director of Partnership for Food Safety Education. "When they get fresh produce home, it's important to clean it thoroughly. Whole fresh produce should be rinsed under running tap water just before eating and produce should be kept separate from meat, poultry, raw eggs and fish to avoid cross-contamination."