different between wholemeal vs wholegrain

English

whole +? meal

wholemeal (not comparable)

(of bread or flour) containing or made from the whole grain, including the bran
Synonyms: wholegrain, whole-wheat

wholemeal (uncountable)

Whole-wheat flour
- 1955, Domestic Food Consumption and Expenditure: Annual Report of the National Food Survey Committee
  As might be expected, the small white loaf was bought mainly by the smaller wholly adult households, who also purchased much more wholemeal, other brown and "other" bread than did any type of family with children.

whole +? grain

wholegrain (plural wholegrains)

A cereal grain that contains cereal germ, endosperm, and bran, in contrast to refined grains, which retain only the endosperm.