Microbiological contamination in chocolate poses a low risk. The risk of Listeria is of little concern to the chocolate industry, because the dairy products used are pasteurized.
The major risk is related to the contamination of cocoa beans by Salmonella. There are three possible origins to theses contaminations:
• Initial contamination
Raw materials: cocoa beans and derivatives, dried fruits, milk and its derivatives, lecithin … Salmonella are destroyed if the raw materials undergo a heating treatment during the process.
• Contamination during manufacture
The origins of contamination are the material, the methods, the environment, and the workforce.
Due to uncontrolled roasting scale. Salmonella is highly heat resistant under relatively low water activity (Aw) conditions. Salmonella are not destroyed during conching.
In general, contamination is very rare, and quality assurance is there to remedy it.