For global catastrophic risks the costs of food storage become impractical for most of the population  and for some such catastrophes conventional agriculture would not function due to the loss of a large fraction of sunlight (e.g. during nuclear winter or a supervolcano). In such situations, alternative food is necessary, which is converting natural gas and wood fiber to human edible food.
It’s impossible to carry all the food you will need for a week unless you’re eating very high density proteins like nuts. Nuts and dried meat are two of the easiest off-the-cuff meals. Canned food has a lot of water that is wasted during the cooking process. Stay away from heavily flavored or salted nuts. The amount of salt present in the unsalted nut mixes is still sufficient enough to replace electrolytes.