Preserved foods include anything that was canned, frozen or otherwise processed when the food was in peak season, for use at other times of the year. Beyond canning individual fruits and veggies, you can also can salsa, jams, jellies, chutneys, broth and more. Some foods do better with freezing (some veggies require blanching first), and items such as pesto, meat pies or even casseroles may be prepared at peak freshness and frozen.
Nutrition: Jams and jellies include a lot of added sugar, and many canned items like salsas and vegetables include added salt. However, these amounts are much more modest than store-bought canned goods. Store-bought items can sometimes contain massive amounts of sodium, sometimes up to 1/3 of your daily recommended value.