I think that you are confusing the meaning of plural with uncountable.
Food is uncountable and is followed by the third person singularverb form e.g. The food in Denmark is fantastic.
Food can be singular e.g. A food I like is chicken.
We can refer to food in a plural sense when we wish to refer to a list of food types or groups e.g. The foods that make make millions of pounds are many and varied. This would rarely be used.