Freshly squeezed orange juice stored in metal jugs (for long periods) could be a storehouse for microbial contamination, according to a new study in Spain. The researchers have observed microbial contamination in orange juice squeezed in bars and restaurants.

The new study, published on Wednesday in the Food Control Journal, states that poor handling of fruits and inappropriate cleaning of juicing equipment in bars, restaurants and other catering establishments could result in food-borne illnesses. It noticed traces of Staphylococcus aureus and salmonella levels in the samples inspected.

The study is meant to issue a warning to those in the catering business to ensure consumer health while recommending that juicers are cleaned and disinfected properly. The researchers advocate consuming freshly squeezed juices but recommend that storage jugs for the juices be cleaned appropriately to avoid any potential microbiological food contamination.

The researchers, from the University of Valencia, explained that juicers and juicing machines have a large surface area with innumerable perforations and cavities that could harbor the growth of microbes, which could, in turn, be picked up by the juice being prepared.

The scientists analyzed fresh orange juice squeezed by machines in catering establishments. They claim that about 43 percent of the samples inspected exceeded the acceptable enterobacteriaceae levels laid down by the food legislations in Spain and Europe.

Isabel Sospedra, the study's author, warned that generally a percentage of orange juice is consumed immediately after squeezing but, as in many cases, it is kept unprotected in stainless steel jugs. 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 team collected 190 batches of squeezed orange juice from different catering locations and analyzed their microbiological content on the same day.

The scientists revealed that 81 percent of the juice samples, kept in metal jugs, presented unacceptable levels of enterobacteriaceae. Meanwhile, another 13 percent showed higher levels of mesophilic aerobic bacteria. The team explained that when the oranges were freshly squeezed and served as fresh juice in a glass, these percentages fall to 22 and 2 percent respectively. In addition, 12 percent of the samples exceeded mesophilic aerobic microorganism levels. Staphylococcus aureus and Salmonella were found in 1 percent and 0.5 percent of samples, respectively.