Human history is built on food. Just about any social occasion or backroom deal, no matter how small, has had some kind of food present. Armies need it to fight, people need it to live, and economies need it to function. The most historically important foodstuffs are more than consumable quantities... they've tipped balances of power in the world.
The foods that changed history come in all shapes, sizes, and flavors - from sweet to salty to savory. However, they always managed to fill a specific need at a specific time. Whether it be a new way of persevering crops, a delicacy for the nobility, or a way to feed the masses, food has been the cornerstone of humanity's foundation.
But what foodstuffs were the most influential of all time? You'd think that would depend on the time and place, but most of the big discoveries still have relevance in today's world.
Bread was everything to the common Frenchman's diet in 18th century Paris. It was so important that bakers were considered public servants and the police controlled bread production. So when there was a massive bread shortage that led to a famine, you better believe everyone was eager to overthrow the government. What followed was known as the French Revolution.
Grain (and by extension bread) feeds the world, and has fed it for almost as long as recorded history. Ancient Egypt's chief export was grain, which made it an incredibly important part of the Roman Empire. It also led to the discovery of beer, which you can bet millions are incredibly thankful for.
The Allies had millions of troops fighting in World War II, which meant they had to find a way to feed them. SPAM was a protein-rich meal that was easy to ship and had a long shelf-life, so it became the breakfast, lunch, and dinner of the guys who beat the Nazis. They got so sick of it, they started making jokes like "Spam is a ham that didn't pass its physical."
Tea was so popular in the colonial world, it literally led to corporate espionage and political revolutions. By the 17th century, the tea had become a staple of British culture which led to a rivalry between European and Chinese manufacturers. Many years later, a heavy tax on tea drove the American colonies to commit one of the inciting incidents of the American Revolution - the Boston Tea Party.