Is it safe to reuse left over chocolate? That's a question that comes up on a regular basis. The short answer is yes, with some qualifications.
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As any candy maker knows, chocolate can be used many times over. It can be melted and re-melted and if handled, stored and re-heated with care, it will last as long as it remains un-eaten.
Two past references worth mentioning here are the previous posts on sugar bloom and fat bloom. Those references cover the care and storage of chocolate, preserving the flavor and appearance.
Should I re-use chocolate left over in my chocolate fountain is more an ethical question than a food safety issue. If I am a caterer or chocolate fountain rental operator and have melted chocolate left at the end of an event, should I save it and re-use it on another rental? Probably not. Even though the chocolate will be safe from most common food spoilage issues, it is more a question of the customer paid for the food product used in your rental so reusing it crosses an ethical line. If you balk at wasting leftover chocolate, offer it to your customer at the end of an event. Or take it home and make use of it personally.
Offering it to your customer isn't much different than if you were catering and had a chafing dish of food left over at the end of your event. The customer paid for it whether consumed or not, it belongs to them.
If you do recycle the leftover chocolate for yourself or your client, let it stand for a few minutes in the chocolate fountain after the fountain has been turned off. That will give time for any bits of food like cookie or pretzel crumbs a chance to settle to the bottom. Ladle the melted chocolate out into another container leaving the very last in the fountain basin to be discarded. You can also pour it through through a wire mesh food strainer to remove any food crumbs that have fallen into the chocolate.
Finally the "EWW" factor. I'll address this in greater detail later, but basically, other than food crumbs, the fact that chocolate has a high sugar content (which prohibits the formation of common food bacteria the same as foods high in acidic content) and that it is kept moving and at a serving temp of around 100 degrees fahrenheit, the "ewww" factor is a matter of perception. Unless cross contamination (meat and dairy) occurs. That would mean no pork chop dipping in the chocolate fountain. A good a reason as any to always use a professional caterer to oversee your event's food service.
