Technion researchers: washing with water does not remove the salmonella bacteria from the parsley

Even washing with a chlorine solution (bleach) failed to remove the bacteria from the vegetable

Researchers at the Faculty of Biotechnology and Food Engineering at the Technion discovered that washing parsley with water does not remove the salmonella bacteria that has stuck to it. What's more - even washing with a chlorine solution in high concentrations failed to accomplish the task.

Master's student Anat Lapidot, under the direction of Dr. Sima Yaron, carried out the research in a greenhouse in the ecological garden at the Technion. "According to our findings, the salmonella bacterium is able to move from water or contaminated soil and penetrate the internal parts of the plant, where it hides. In addition, the bacterium produces an external organic shell for itself that protects it from the environment," she says. "This increases the survival of salmonella in parsley, more than bacteria that have not developed this ability."

The researchers concluded that preventing the creation of the envelope may add to the safety of the product, "however, it is not the main solution to preventing the bacteria from sticking to the plant", as they said. ” Once the bacteria adheres to the plant, conventional cleaning agents will not be able to remove it effectively. Therefore, if the parsley is contaminated, it doesn't matter at all if the housewife washes the parsley well with water, or if she doesn't - most of the bacteria will remain there anyway." They highlight the importance of preventing infection in the field, at every stage of growing and marketing.

The researchers grew the parsley in a greenhouse, under controlled conditions. The parsley was watered three times in water with salmonella. Irrigation was carried out by drip, so that there was no direct contact between the water and the leaves. However, after watering, bacteria were found in the leaves and stems, which survived there even three weeks after watering, or during storage in the refrigerator. It turned out that the salmonella bacterium's ability to penetrate into the plant and create a protective organic shell around it prevents its removal from the parsley and it even survives treatment with a concentrated chlorine solution (bleach). "Following the increase worldwide in the rate of food poisoning resulting from eating vegetables, fruits and herbs, the focus must not only be on developing innovative cleaning methods, but also on preventing contamination in the field," say the Technion researchers.