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Money handling in food service operations

An aspect of food service which frequently causes consumer comment is the way a food handler prepares the food, takes money for the purchase, returns change to the customer and then prepares food for the next customer. This is most noticeable in sandwich bar operations but is by no means restricted to these outlets.

Two recent studies in the United States have endeavoured to determine the likelihood of currency serving as a vehicle for transmitting potential pathogens to hands and food.

The first of these (Infectious Medicine 14. 1997. 574) involved swabbing and culturing from various coins and paper currency collected at random from doctors and other employees at a New York hospital.

Coagulase-negative staphylococci were recovered from only 3 of 102 coins examined. It was the only organism isolated from 2 coins and on one coin it was mixed with Bacillus species, i.e viable bacteria could be cultured from only 3 per cent of coins examined. Eleven of 100 paper notes yielded coagulase negative staphylococci. It was the only organism found on 6 notes while Bacillus species were recovered from a further 4 notes. One note was positive for coagulase negative staphylococci and Bacillus species in addition to one corynebacterium species.

These results are much lower than and different from those obtained in an earlier study (J. American Medical Association. 219. 1972. 1201-1203) where 70 per cent of coins and 70 per cent of bank notes were contaminated with many types of bacteria.

The second current study (J. Food Protection 62. 1999. 805-807) takes a different experimental approach. The researchers inoculated the surface of coins with the pathogens Escherichia coli 0157:H7 and Salmonella enteritidis to determine the survival of these organisms on the coins. The inoculated coins were dried under a laminar flow hood for 2.5 hours at 29°C. After this time duplicate samples were aseptically removed and the inoculated bacteria counted.

At the completion of drying, coins and controls were held at 25°C and 40% relative humidity for survival studies. Salmonella enteritidis cells proved more sensitive to drying than E. coli 0157:H7 with a 1000 to 10,000-fold decrease of salmonellae compared to an approximate 100-fold reduction of E. coli on the coin surfaces during the 2.5 hour drying time.

During subsequent storage at 25°C, E. coli 0157:H7 survived for 7, 9 and 11 days on surfaces of pennies, nickels, and dimes and quarters respectively. The initial population per coin surface was approximately 10⁵ cfus. Salmonella enteritidis survived for 1, 2, 4 and 9 days on the surfaces of pennies, nickels, quarters, and dimes respectively. No similar studies on Australian currency have been published. For the purposes of comparison Australian 5, 10, 20 and 50 cent coins are 75 per cent copper and 25 per cent nickel. One and two dollar coins are 92 per cent copper, 6 percent aluminum and 2 per cent nickel.

Dimes and quarters are made up of a pure copper core and an outer layer of 75 per cent copper and 25 per cent zinc alloy. Nickels are an alloy of 75 per cent copper and 25 per cent nickel. Pennies are 95 per cent copper.

The authors of the above study conclude that the pathogens tested are subject to inactivation on coin surfaces by drying and by the bactericidal effect of copper. They also draw attention to the apparent low infectious dose of E. coli 0.157:H7 and recommend that food handlers should use an intervention treatment such as washing hands after handling coins and before handling food.

This is not practical in many situations and at least the first study examining natural contamination of coins should give some reassurance to consumers.

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Prepared by Keith Richardson and Beverley George
Food Science Australia
PO Box 52, North Ryde 1670. Tel +61 2 9490 8397 Fax +61 2 9490 8499
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