I briefly knew a guy who was a buyer for a large supermarket chain. His job was to make deals to get the massive amounts of grain for the future store brand cereal production. This is a huge amount of food production, and making sure you have the supply booked up - low cost imports from anywhere they can be found, basically (this was not a US chain, so a lot of grain was imported) - way in advance was important.
Amusing was his nonscientific (though not necessarily incorrect) views of the product. "It's all poison. Do not eat it." But more relevant to now, you can get the impact of things like Brexit uncertainty and threatened future tariff changes on these types of businesses. Supply contracts start shifting long before they actually take effect, and even if they never do.
