Well, that isn't really true. Dried peas, pearl barley, brown rice, corn meal, and parched corn, think corn nuts, whole oats and all sorts of dried fruit and produce were available in the 18th century.
In the years I have been trekking and rendezvousing I have never had a problem with bad food or meat due to carrying them in a linen sack without any sort of plastic "protection".
The same with fresh fruit and veggies, though they are usually consumed the first coupla days out.
Nor have I had a problem with meat, especially Jerky, though fresh meat is often shot or trapped.
The main difference in today's food vs food in the 18th century is the preservatives, high fructose corn sugar, dyes and fat content of prepared foods.
God bless