When COVID-19 first emerged to cause a historic global pandemic, questions naturally arose about how the virus was spreading.
One possibility was that people were picking it up from contaminated surfaces, a prospect that led to a wave of deep cleaning, panic buying of hand sanitizer and questions about whether it was safe to use. open mail or unpack groceries without wiping them first.
Now new research from the UK’s Food Standards Agency (FSA) which looked at whether the virus could persist on groceries suggests that being careful with certain food items may not be a completely idea. crazy after all.
The foods that were tested, according to the research team, “are usually sold loose on supermarket shelves or uncovered at deli counters or market stalls, they can be difficult to wash, and they are often eaten without further transformation, i.e. without cooking”.
They also tested food packaging materials that are either very common or used on products where consuming food may involve direct contact between the mouth and the packaging.
Scientists artificially applied the infectious COVID-19 virus to the surfaces of food and packaging, and measured changes in the amount of virus present on these surfaces over time. The surfaces were tested in a range of temperatures and humidity levels over periods of time that reflected their typical storage conditions.
The concentration of the virus applied to the objects was representative of the respiratory droplets that landed on them, for example if an infected person coughed or sneezed nearby.
The researchers found that survival of the virus varied between grocery items, but for most foods tested, they noticed a “significant drop” in contamination levels after the first 24 hours.
Some products, including peppers, bread, ham and cheese, had an infectious virus detected several days after they were contaminated. On some surfaces, such as croissants, the virus remained present and transmissible for hours.
The study authors broke down their findings by food category.
Fruits and vegetables
FSA scientists said previous research had suggested that COVID-19 might survive cold temperatures better than ambient food storage temperatures.
“But for the fresh vegetables presented in this report, the difference between cold survival and ambient conditions is not so clear,” they said in the report published this week.
They said the virus survived the longest – up to five days – on broccoli when stored at 23 degrees Celsius (73 degrees Fahrenheit) with a humidity setting of 31%. Meanwhile, COVID lived on the peppers for up to seven days when the peppers were chilled to 6 degrees Celsius.
On raspberries, the virus survived for varying lengths of time depending on conditions, but the report’s authors noted that the pitted surfaces of the fruit “may protect the virus from desiccation.” Apples, however, may have antiviral properties due to chemicals in their skins, the researchers noted, citing previous studies.
Bakeries and pastries
According to the study results, COVID-19 lasts longer on white bread crusts than on brown bread crusts. They speculated that this could be due to substances present in the higher levels of fiber in brown bread.
Pastries that were tested, including croissants and pain au chocolat, quickly inactivated the virus, the researchers said. They speculated that this could be because the baked goods are coated in a liquid egg wash that may have an inhibiting effect on COVID-19.
“Eggs have one of the highest levels of arachidonic acid in the human diet,” the study authors said. “It has been suggested that arachidonic acid and other unsaturated fatty acids, which are present in high levels in eggs, could serve as antiviral compounds.”
The study found that the virus had a very low survival rate on olives, even just one minute after contamination.
The research team noted that, as with the apples, it was likely chemicals in the olive skins that inactivated the virus.
Meanwhile, FSA scientists said deli meats high in protein and saturated fat with high water content promoted longer survival of the virus – noting that previous research had shown that COVID-19 could survive on processed meats for 21 days in a refrigerator.
“The long survival time of SARS-CoV-2 on slices of ham and cheddar cheese, with their high protein, saturated fat and water content, highlights the importance of good food handling to avoid any contamination with the virus before consumption,” the study said. the authors said.
The researchers found that COVID was able to survive for up to a week on plastic surfaces and several days on cardboard. The virus was thought to be able to survive on aluminum cans for hours rather than days, they said.
However, they noted that the foods included in the study were artificially contaminated and therefore did not reflect the levels of contamination that can be found in grocery stores. They added that foods with lower levels of contamination would take less time for the virus to decline to undetectable levels.
Centers for Disease Control and Prevention (CDC) experts say COVID is primarily spread when an infected person exhales droplets containing the virus, which are then inhaled by someone else or end up in the eyes, the another person’s nose or mouth.
While the CDC also says the virus can be spread via contaminated surfaces in some cases, the organization says there is currently no evidence that handling or eating food can spread COVID-19.
“Follow food safety guidelines when handling and cleaning fresh produce,” the organization advises. “Do not wash the products with soap, bleach, disinfectant, alcohol, disinfectant or any other chemical.”
While the FSA researchers acknowledged that several studies had found the risk of infection via contaminated groceries to be “extremely low”, their findings showed that certain foods and food packaging materials “can withstand a infectious virus for a significant period of time”.
“There is a possibility of transmission through contaminated food if the food comes in direct contact with the mouth and mucous membranes,” they said, but noted that the implications of their findings were unclear because inhalation respiratory droplets was considered the primary route of COVID infection.
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