Why foods go bad

Should humanity face a nuclear apocalypse of worldwide war, we need to understand which foods might be safe for survivors to eat, and how long the foods will last.

To understand this, we need to ask what makes food spoil.

Most foods spoil because of the growth of microbes. Preserving food is an attempt to limit microbial growth. Food can be preserved by drying, salting, chilling, or storing in air-tight containers.

• Drying is the most effective because microbial growth is inhibited.
• Salting is effective because it removes moisture, creating an environment where microbes cannot survive.
• Sugar coating can prevent bacterial cells from functioning correctly.
• Storing in air-tight containers is less effective because there are probably a lot of microbes on the food before you put it in the container. Some microbes are anaerobic, meaning they don't need oxygen.

Preservatives are used in foods to extend their shelf lives. One of McDonald's Big Mac in Iceland is an example of a long-lasting processed food. It has been on display since 2009, in a glass box. Preservatives that has been discontinued by McDonald's are:

• calcium propionate that prevents mold growth on bread.
• sorbic acid that also inhibits mold from cheese
• sodium benzoate, which inhibits the growth of bacteria in the Big Mac special sauce.

• Twinkies will last no longer than similar treats. One Twinkie has been kept in a time capsule for up to 44 years.
• Honey is almost impossible to spoil because it is high in sugar and low in water. Some honey samples are 3,000 years old.
• Very fat-rich foods like butter and cheese, tallow or oils can last for a long time. Bog butter, a highly fermented butter, is up to 4,000 years old.
• The world's oldest champagnes, 200-year-old bottles of Clicquot, was perfectly palatable.
• Ancient frozen flesh may look perfectly edible but quickly becomes putrid after defrosting.
• Fish is even worse at surviving the freezing process. Meat tends to have all kinds of microorganisms, which makes it unsuitable for long periods of storage.

• Unless a nuclear or chemical incident has contaminated the food, all foods that are not in the fresh aisle can be eaten with confidence. That is tinned or dried foods and even frozen foods. Vacuum packed would also be useful.
• Slow-dried food could still harbor microbes. Spray-dried or freeze-dried foods, like instant coffee grounds and fine powders, will last longer.
• Food designed for space travel could be right. Space food is dehydrated and vacuum-sealed.
• General-purpose army rations are good for three years at 80F (27C).
• Other food replacements to consider are Huel. Huel is a company that offers a complete diet in powder form, uses freeze-drying and milling to create powders with no moisture in them.