This document is dated August.
"Certain types of fresh food supply will decrease. Critical elements of the food supply chain (such as ingredients, chemicals and packaging) may be in short supply. In combination, these two factors will not cause an overall shortage of food in the UK but will reduce availability and choice and increase the price, which will affect vulnerable groups"
In September, Michael Gove the minister in charge of no deal brexit planning claimed that some food prices would go down, but some may go up and that there should be no shortage of fresh food.
inews.co.uk/news/brexit/no-deal-brexit-food-prices-increase-michael-gove/
This contradicts the Yellowhammer planning document. This could mean that Gove lied, or hadn't read the document, or mis-understood it.