Replied By Stuman (San Diego) on 10/29/2019
I use the black beans from the Mexican market. They work great.Replied By Pam E. (SW Calif) on 12/14/2022
In the introduction to this blog it says which kind is used doesn't matter: "The specific kind of black beans does not seem to be critical, as all such dark beans are rich in anthocyanins ..."