a variety of 是加复数的,但是food比较特殊,既是可数名词,又是不可数名词,a variety of food
various of这个表达法,因为various本身是形容词,所以不必加of.
可以这么说,a variety of(多种的) = various(不同的,各种各样的)
如；There are a variety of animals in the zoo.
=There are various animals in the zoo.