To understand incidences of foodborne illnesses in association with vegetables, microbiologists have discovered that some pathogenic viruses can adhere to the surfaces of fresh produce.
To assess the extent of the risk, researchers looked at 24 common salad vegetables found in the U.S. X-ray images and other forms of analysis were undertaken to see if there was any pattern between the morphology and chemistry of the vegetable surface and the ability of pathogenic viral particles to adhere to the surfaces. Vegetables and fruit were examined after being freshly picked and before any subsequent washing or chemical treatment.
Additional studies were carried out where certain fruits and vegetables were challenged with pathogenic viruses. Here salad greens and tomatoes were inoculated with human rotavirus. This virus causes a number of ill-health effects including diarrhea and vomiting, as well as fever and abdominal cramps.
The study then proceeded to see how easy it was to remove the viruses from the surface of the produce. The fruit and vegetables were subject to a double rinse using a salt solution.
All of the studies were then correlated and examined to see if there were any patterns. It was found there was a relationship between the ability of the virus to stick to the surface and the roughness of the surface. The rougher the surface, then the more viral particles became fixed to the surface and the more rinses were required to remove the viruses.
Another pattern that emerged related to surface chemistry. If the plant had a waxy outer layer, then it was harder for a virus to become fixed to the surface. This is because the wax renders the surface hydrophobic, which leads to the whole leaf surface becoming harder for viruses to attach to. The data suggested there were 1000-fold fewer viral particles on waxy surfaces compared with rough surfaces.
According to a review of past work, these studies represented the first time an attempt had been made to link pathogenic viruses and the surfaces of vegetables. The outcomes will be important for the way fruit and vegetables are processed, in terms of rinsing, before they reach consumers. Hopefully the knowledge will lead to a reduction in cases of food poisoning.
Further studies are set to take place using pathogenic bacteria, such as Escherichia coli, to determine if the effects are similar.
The research was carried out at the University of Illinois and the findings are published in the science journal PLOS One. The paper is titled “Influence of Epicuticular Physicochemical Properties on Porcine Rotavirus Adsorption to 24 Leafy Green Vegetables and Tomatoes.”
