A bulletin for the Australian Food Industry May 2002
Contents: Salmonella in chocolate | Hazards in international trade | Children and microbial foodborne illness | International spread of foodborne illness | Sanitizers and fresh produce | Supplement: Acrylamide detection in starchy foods
Salmonella in chocolate
Although the risk of salmonellosis from chocolate products is comparatively low, several incidents involving salmonellae in chocolates have been reported over the years (Journal of Food Protection 40 1977 718-727). Chocolate was one of the first products that provided strong evidence that large numbers of salmonellae were not necessarily a prerequisite for human infection and that food ingredients may protect Salmonella against the acidic conditions of the stomach. Even small numbers of salmonellae present in the product could colonize the lower gastrointestinal tract and produce clinical symptoms (Lancet 1 1976 66).
The most recent well documented outbreak of Salmonella food poisoning associated with chocolate (Eurosurveillance Weekly 3 17 January 2002) confirms that international trade has the potential to introduce new or different food safety risks into the food supply of importing countries. From mid-October 2001 to mid-January 2002 health authorities in Germany received 373 reports of Salmonella oranienburg infection. One hundred and fifty four of the reported cases were younger than 10 years. Health authorities conducted a case-control study initially involving 60 cases (i.e. people who had shown symptoms of foodborne illness) and 62 controls who had shown no signs of illness.
Cases and controls differed significantly with respect to having consumed chocolate in general, having shopped at a particular supermarket chain and having consumed chocolate bought in that supermarket chain. Several other cases not included in the study reported having eaten a specific brand of chocolate distributed exclusively through the same supermarket chain.
Human isolates from outbreak cases, and strains from left over chocolate that had been consumed by cases before the onset of illness, were identified by laboratory techniques as the same strain of S. oranienburg. The investigation into how the chocolate became contaminated is continuing.
Destruction of Salmonella or other pathogens in chocolate once contaminated is a difficult if not impossible task owing the low water activity of the product (Journal of Food Protection 40 1977 718-727). Heat treatments, including dry roasting of cocoa beans and conching of chocolate, do not equal the effectiveness of bacteriological control of raw materials and stringent plant sanitation.
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