If you are surprised to learn that every year an estimated 48 million people in the U.S. get sick from the food they eat, videotapes of cooks preparing a meal, part of a new study, will make you wonder why there aren't many more.

The study found that 90% of the participants contaminated fruit salad with bacteria from raw meat while cooking a meal. About one-quarter of the fruit salads were heavily contaminated. The study used a harmless tracer organism in place of live bacteria, but one that could have been, in real life, salmonella.

Many home cooks did not wash their hands before beginning meal preparation, and even more did not wash their hands after handling raw meat packaging or trash.

Cooks spread the bacteria to faucets, refrigerator and oven handles, counter tops and salt shakers. But the most contamination was found on the kitchen towels, suggesting they were the likeliest route by which bacteria moved from meat to fruit salad.

Even people who used paper towels instead of cloth kitchen towels re-used them multiple times during the meal preparation.

The most likely explanation for the spread of the bacteria throughout the kitchen was poor hand washing. Many home cooks did not wash their hands before beginning meal preparation, and even more did not wash their hands after handling raw meat packaging or trash.

Some cooks did wash their hands after handling the meat, but few washed them for 20 seconds with soap, creating a superb opportunity to transfer bacteria to the towel when they dried their hands, bacteria they would later spread around by re-using the towel.

Apparently, cooks still have a lot to learn when it comes to food safety. And handwashing.

The purpose of the study was to test the types of messages that lead to safer food handling practices. And while the researchers did find a small improvement in people who received messages, poor personal hygiene in the kitchen stood out.

More than 130 people were filmed while cooking a meal that included either raw ground beef (for meatballs) or raw chicken and a ready-to-eat fruit salad. Filming was done with four cameras inconspicuously placed throughout the kitchen. People knew that they were being filmed but did not know that the meat had been inoculated with Lactobacillus casei, a non-harmful bacterium that's found in the human mouth and intestine and is also often present in yogurt and cheese.

Afterwards, kitchen surfaces were swabbed down and the swabs were analyzed for their bacterial content.

On the brighter side, only four people used the same utensils on both raw and cooked meat without washing them in between, and only three cooks used the same utensils on both raw meat and fruit salad without washing them first. But seeing is believing. Given that 90% of the cooks contaminated their fruit salad with bacteria from the meat shows just how far cooks have to go.

The cameras also recorded many people using their cellphones during the meal preparation, often without first washing their hands. Though not yet established as a source of food contamination, this raises the possibility that cellphones can also spread harmful bacteria from contaminated food.

The study (PDF) appears in Food Protection Trends.