Which fungus is traditionally used to make red yeast rice?

Which fungus is traditionally used to make red yeast rice? Monascus purpureus is the answer.

This reddish-purple mold is cultivated on rice to produce red yeast rice, also called red rice koji, angkak, or ank-kak. As the mold grows, it releases pigments that color the grains and creates metabolites used in traditional fermented foods, rice wines, vinegars, and food coloring.

The practice has a long East Asian history: red yeast rice has been used for more than 1,000 years, with Chinese medicinal use often associated with the Tang dynasty, around AD 800. It is also used to color foods such as fermented tofu and Peking duck.

The fungus is often discussed because it can produce monacolin K, a compound chemically identical to lovastatin. That connection explains modern supplement interest, but products vary greatly in their contents and may also raise safety concerns. Related Monascus species, including M. ruber and M. pilosus, have industrial uses, yet M. purpureus is the conventional quiz answer for this traditional food.