For those who still think that reductions in food supplies are just a temporary hinderance and that they'll just buy a little less or buy whatever is in stock, consider what happens to your personal shopping if there is a No Deal Brexit.
The government planners are working on a Channel Crossing capacity of only 13% of current levels - 1,300 trucks a day instead of 10,000 trucks a day. They are also drawing up plans for a State of Emergency (in 1970 when there was a dockers strike, the Army put 36.000 troops on standby) and possibly Martial Law, with curfews, restrictions on cash and card payments, restrictions on fuel and travel and so on.
Now imagine a typical supermarket which usually receives 10 truck-loads a week of fresh foods from the EU. Peppers, tomatoes, potatoes, mushrooms, peas, beans, apples, oranges etc. These arrive at the rate of approx. 2 trucks a day, and as the supermarkets are extremely good at predicting demand, this represents the normal demand for a week,
After Brexit, due to the reduced capacity across the Channel, only just over one truck in ten makes it over the Channel. So this supermarket now only receives one truck-load a week rather than ten - and one load a week represents just half a day's normal sales.
So the truck arrives at the supermarket one morning at 7.00 and is unloaded ready for the shop opening at 9.00 (the curfew has ended 24-hour trading) where a hundred people are already queuing.
If all goes well, the shoppers file in, buy their normal amounts and the new stock is sold out by 12.00 midday. Those people who were unable to get to the shop - people at work, those housebound, those with no transport etc. probably won't have made it, and since the next delivery will not be for a week, these will now all go without for a week.
Of course, it might not all go well. Some shouty person with a Transit van and a couple of burly mates might decide to attempt to buy the whole lot in one go. Will the £8-an-hour security guy stand in the way, will the till-staff get into an argument with them, or will the other shoppers attempt to prevent this? How long before chaos and fights break out?
Repeat the scenario for all foodstuffs that have foreign ingredients and the scale of the problem becomes clear. E.g. Heinz may now have 3-months worth of American beans and Italian tomato paste in their big factory in Wigan but after 3 months, this stock will be used and thereafter they can only make 10% of their normal production of baked beans.