Forbeo wrote in
ups.com:

Does anyone have tips for preserving packaged baked goods
without using preservatives in the dessert itself? We have
been trying to add to the shelf life of our products
without adding artificial preservatives to the ingredients.

Any information you could provide me would be greatly
appreciated.

freezing comes to mind.
you are making a specialty product. it shouldn't need a long
shelf life. brownies are good for about a week if well
wrapped, maybe a bit longer if refigerated.
lee