written by Alex Cochez MD
June 2021.
Alex' Linkedin profile
Anthocyanin dissolves in water and (alkaline) water will color black. Simple as that.
Soaking rice overnight results in a loss of 15-20%.
At home we don't soak our rice and many of our customers don't do either. The longer one soaks, the more whitish the grain becomes.
The core of the grain, the endosperm, contains the brown-whitish macro-nutrients (carbs, protein).
Anthocyanin is a pH INDICATOR. When mixed with an acid, the solution colors reddish.
Vinegar is such an acid solvent and therefore 'the vinegar test' is the golden standard to verify the authenticity of any colored rice variety at home.
Dissolve some black rice in vinegar and in 3-5min the solution will color red.