There are many countries in the world which actually grow food and, believe it or not, they are all not in the EU so we will still be importing from them.
If the EU find they are being left with excess fresh food because there is some delay at the ports ( on their side) then perhaps they may consider it was their fault for not giving the beat deal to their best friend and ally. We can eat all the lovely British grown food, if there is some delay on our side, ourselves.
Looking at another thread on here about obesity, I think a few food shortage may do some people some good! If there are food shortages, they will more likely be caused by selfish panic buying.