Keeping Donuts fresh
Instead of fresh eggs, use powdered egg yolks. 
Make sure any oils you use are high in saturated fats, such as palm or soybean oil — and use their hydrogenated forms wherever possible.
Replace some of the flour with polysorbate thickening agents and gums of xanthan, guar, and cellulose.
Add moisturizing agents such as glycerin.
Finally, be sure to include one or more chemical preservatives — potassium sorbate, for example.


Reference: Entenmann's Donuts List of Ingredients