Chinese soy sauce production begins with soybeans (sometimes wheat-blended) fermented over months or years in salt brine with the mold Aspergillus oryzae (qu, 曲) as the primary fermentation organism. The result — after pressing the liquid from the fermented solids — is a raw soy sauce (shen chou, 生抽) of immense complexity. Light soy sauce (sheng chou, 生抽) is the first pressing — thinner, saltier, with bright umami and a clean, complex flavour. Dark soy sauce (lao chou, 老抽) is either a subsequent pressing (thicker, less salty, more complex) or light soy sauce with added caramel and often molasses — darker, more viscous, less salty, used primarily for colour rather than seasoning.
Understanding the difference: Sheng chou (light/raw): The default Chinese soy sauce for seasoning, marinades, dipping sauces, and finishing. Saltier (18-20% sodium) and lighter in colour. Lao chou (dark/old): Used primarily for colour — adds the deep mahogany colour to red-braised dishes, fried rice, and dark soy preparations. Less salty. Should not be used as a primary seasoning — too much lao chou makes food bitter and overly dark. The premium brands: Lee Kum Kee Premium (Pearl River Bridge variety) is widely available and consistently good. Kimlan (金兰) soy sauce is the Taiwanese standard. Kikkoman, despite being Japanese, is widely used in Chinese cooking outside China. Chinese soy sauce and Japanese soy sauce are produced by the same basic process but have distinct flavour profiles — Chinese light soy is typically saltier and slightly more assertive; Japanese shoyu is slightly sweeter. Double-fermented soy (双重发酵): Some premium Chinese soy sauces undergo a second fermentation phase, developing even greater complexity. Shrimp soy (虾子酱油, xia zi jiang you) — soy sauce infused with dried shrimp roe — is a premium Cantonese condiment.
Fuchsia Dunlop, Every Grain of Rice (2012); Fuchsia Dunlop, Invitation to a Banquet (2023)