Remove powdered foods from their original containers and repack small quantities in double plastic bags. Between the two bag layers, slip in an identification label and the mixing instructions.
Transfer spices from large containers into clean prescription bottles or plastic film canisters; label the containers and lids.
To protect eggs, carry them in a container filled with flour.
To lighten your backpack, carry powdered egg, which is as nutritional as fresh egg and is easier to store. For the same reasons, take powdered instead of liquid milk and potatoes, and dried vegetables and fruit.
A stream can serve as a refrigerator; put the food in well-anchored waterproof bags.