Preservatives for longer shelf life

I am doing a consultancy for a chocolate store owner who is looking at adding preservatives to his fillings. Although this is totally against my chocolate religion, I was wondering where I can get info regarding preservatives? What kind suits best each filling without greatly affecting the taste...

I also wonder, will the addition of glucose to a nut based filling (gianduja/praline) help increase the shelf life?

updated by @omar-forastero: 04/20/15 03:23:42AM

I don't believe adding glucose to a nut-based filling will help much. There's very little free water in a confection like that to begin with.The shelf life of ganaches, on the other hand, will greatly benefit from products like invert sugar, glucose, alcohols and acids.A good reference is chef Peter Grewelling's book Chocolates and Confections: Formula, Theory, and Technique for the Artisan Confectioner