Adding red or black rice to extract brews

[Stephen Power]

I've been brewing with extracts (mostly Coopers) for years. I've just recently been to Japan and I really enjoyed some of their beers which have black and / or red rice added to them (e.g. Konishi Garnet Rouge, Hitachino Red Rice Ale).

I wonder if anyone has added rice to their extract brews and if so, how did you convert the rice starch into sugar. As I understand it, you need to add some enzymes or something to the cooked rice. Please advise on which enzymes (or other methods) I should use.

Thanks in advance for any advice.