Epidemiologists have more difficulty accurately determining the food vehicle during a foodborne illness outbreak associated with mixed foods, such as mixed berries.
The viral and parasitic pathogens that have caused outbreaks associated with consumption of berries are difficult to detect in foods, said Palumbo et al.
Laboratory methods used to find these pathogens have only recently been developed or are still under development.
Researchers gave data of foodborne illness outbreaks associated with common berries as the food vehicle from 1983 through 2012.
The aim was to be a reference for those concerned about safety of fresh and frozen berry products.
They gave two tables, one with specific berries being identified as the food vehicle and the other lists the reported outbreaks in which berries were the ‘likely’ food vehicle.
Providing information for those who grow, harvest, process, transport and serve berries to consumers is important to improve science-based programs for the supply chain, said the researchers.
In table one, the recent outbreak of Norovirus in Germany in frozen strawberries from China is listed.
It sickened 11,200 people as the berries were delivered to almost 500 schools and day care centres in Eastern Germany.
Frozen raspberry pieces from Poland were identified as the source of a Norovirus outbreak in 2005 in Denmark which led to 973 people falling ill.
An outbreak of Hepatitis A in fresh blueberries in New Zealand in 2002 which sickened 43 and killed one from a likely source of infected food handlers or contaminated groundwater.
No kill step
When berries are picked for fresh consumption, they are placed in retail containers in the field or packed in a packinghouse without washing because they are highly perishable.
Berries may be washed before freezing, but they are not usually blanched or heat-treated unless they are used in preserves or other processed products.
This means there is typically no “kill step” that would eliminate pathogens in fresh or frozen berries.
Source: The Institute of Food and Agricultural Sciences (IFAS)
Authors: M. Palumbo, L. J. Harris, and M. D. Danyluk