Ideas for preservatives for making additionally shelf-stable.

[rugercpl]

A friend with a restaurant/bar is asking if snack sticks can be made with additional preservatives to curing/smoking/cooking/fermenting (or using citric acid) so that they can be left in a jar on the bar for sale. Has anyone used anything additional in their recipes such as BHT or anything other food preservatives? This might also be a technique for those roughing it without constant Refridgeration such as the off-grid community. Thx in advance!