Hong qu (红曲, red yeast rice) is cooked rice fermented with the mold Monascus purpureus, which produces a deep crimson-red pigment and secondary metabolites (including lovastatin, which has cholesterol-lowering properties). Red yeast rice has been used in Chinese cooking and medicine for at least 1,200 years — it is the colouring agent in Fujian hong qu jiu (red yeast rice wine), in nan ru (red fermented bean curd, where the red colour comes from hong qu), and in certain Cantonese and Fujianese red-braised preparations where a more complex colour and flavour than soy sauce alone is desired.
Culinary use: Hong qu is used primarily as: (1) A natural red colouring agent in red braising preparations — a small amount added to the braising liquid produces a deeper, more complex red-orange colour than soy sauce alone. (2) A fermentation starter for hong qu jiu (Fujian red yeast wine) and nan ru (red fermented tofu). (3) A flavouring in certain Fujian and Cantonese pork preparations — the fermented notes of hong qu add depth to the braise. Hong qu powder can be added directly to marinades or braising liquids. Hong qu rice (the whole grains) can be ground into a paste and used in the same way.
Fuchsia Dunlop, Land of Fish and Rice (2016); Fuchsia Dunlop, Invitation to a Banquet (2023)