Nope, it's about shortages of food and what people can do to be more self reliant.
Learning how long foods you already have can stay edible is a huge part of not starving during food shortages. Doing these exercises before you need them may save your life.
Despite the salesman at the appliance store being certain, most vegetables and fruits will stay edible, as long as you don't get them into direct sun or let the flies eat them, for at least 2 or 3 days.
Obviously bananas, for instance, tend to go soft rather quickly, but you can keep most of the banana rather edible for at least a full day, if you keep the uneaten part inside the covering and cover it with a cloth to keep flies out.
Citrus fruits will dry a hard skin over any slices taken out of the entire fruit, keeping most of the fruit for weeks even.
Cooked meat, cooked beans, these tend to get bad within a day, but if they are hot when the pot is opened and closed hot, and then placed in a cool spot, you can normally boil the pot again the next day and there is no serious risk to a young healthy person.
Many veggies will air-dry simply by slicing them thin enough and keeping them from bugs, under a fan where possible.
Numerous root veggies have edible leaves, often edible seed pods, that can fill your stomach between heartier meals, and give you vitamins you need, and they often only take a couple of weeks to get to where they make a decent addition to your dry goods.
Except for summer months, or those near the equator, a gallon of pasteurized milk can stay consumable for a number of days, as long as it's kept cool.
Opening the gallon to allow oxygen in, will normally' keep it from growing the worst stuff, and once it starts to curdle, it can be used to make yogurt or clotted (cottage) cheese, then often onto feta, and finally parmesan (if nothing else for cooking to kill off any living cells).
Learn the stages of testing for allergens/poisons in foods.
As I heard, it goes,
Inspect and waft smell (not deep sniff in the container or the bush, use your hand to push the air to your nose, not stick your nose in) on first encounter,
dab on the back of the hand and watch for one day.
then lick and wait a day,
then nibble and wait a day,
if no response, use in small batches the first day
then if no response, eat until something changes, it should be safe