Which type of noun is food?
Regarding this, is food an abstract noun?
Abstract noun of food can be foodie. However, food is a concrete noun with physical substance. Hence, the abstract noun of food is not available. But if we talk about the attributes, then a person can be called foodie.
Secondly, is food a plural noun? Food in its commonest sense is a non-countable noun, with all the effects of that. It's already a plural. You would eat "some food" not "a food". You would say "less food" not "fewer foods".
Hereof, is food a countable noun?
Food is uncountable in general use, as it is in your examples. Like most non-count nouns it can be countable when considering types of food. In this case it takes the plural foods, and may take the indefinite article, a.
Is food an adjective?
"Edible" is a broader term, not specifically related to food prepared in the kitchen. But then some things are (barely) edible but would not be considered food. "Comestible" is usually used as a noun, but it is really an adjective.