I’ve always been wary of those fresh squeezed juice places; and those infomercials where all the dirty carrots, oranges, apples and anything else are tossed in for power juice.

Scientists from the University of Valencia in Spain analyzed 190 fresh orange juice squeezed by machines in catering establishments and found that 43% of samples exceeded the acceptable level of enterobacteriaceae, 12% exceeded mesophilic aerobic microorganism levels, Staphylococcus aureus was found in 1% of samples, and salmonella was found in 0.5% of samples.

Isabel Sospedra, one of the authors of the study appearing in Food Control, warns that, "generally a percentage of oranges juice is consumed immediately after squeezing but, as in many cases, it is kept unprotected in stainless steel jugs."

The scientists found that some juices that were kept in metal jugs presented "unacceptable" levels of enterobacteriaceae in 81% of cases and in 13% of cases with regards to mesophilic aerobic bacteria. However, when the freshly squeezed juice is served in a glass, these percentages fall to 22% and 2% respectively.

“It must also be borne in mind that juicers and juicing machines have a large surface area and lots of holes and cavities. This promotes microbial contamination, which is picked up by the juice as it is being prepared."

The researchers recommend that oranges are handled correctly, that juicers are washed properly and that the orange juice is served immediately rather than being stored in metal jugs.

In 2009, Spaniards drank 138 million litres of orange juice (according to data provided by the Spanish Ministry of the Environment and Rural and Marine Affairs), 40% of which was freshly squeezed and consumed in catering establishments.

A table of juice-related outbreaks is available at http://bites.ksu.edu/fresh-juice-outbreaks.

Sospedra, J. Rubert, J.M. Soriano, J. Mañes. "Incidence of microorganisms from fresh orange juice processed by squeezing machines". Food Control 23 (1): 282-285, 2012 (ya disponible on line).