When using "sugars" (glucose, maltodextrin, etc.) or any organic matter (like gelatin) as "reducing / stabilizing / capping agent" it must be understood that mold (as all fungus) use it as food, and will thrive on it.
The most efficient and safe way to kill fungus is to add little colloidal silver to is, whether it's colloidal gold you make, or if you make molar solutions of any such reducing / stabilizing / capping agent.
Adding colloidal silver is also a good choice for those of you who make home-made jam, juice, or whatever that is cooked and preserved, instead of using chemical preservatives. And also as an alternative to sulphur as a way to stop the fermentation process when making beer or wine.