Japan (sake production by-product; culinary use documented from Heian period)
Sake kasu (酒粕 — sake lees) is the pressed residue remaining after sake is produced: a white, paste-like solid containing 8–14% residual alcohol, live yeast cells, amino acids, enzymes, B vitamins, and significant umami compounds. Its culinary applications are extensive and span from pickles to dessert beverages. Kasuzuke (粕漬け — lees pickle): vegetables, fish, and meat marinated in sake kasu mixed with salt, sugar, and mirin — the enzymes tenderise protein, the amino acids penetrate and season, and the alcohol acts as preservative. Narazuke (奈良漬け) is the most famous kasuzuke, aging vegetables in sake lees 1–3 years to develop extraordinary complexity. Kasujiru (粕汁 — lees soup): salmon, root vegetables, and konnyaku in a dashi-miso soup enriched with dissolved sake kasu — Niigata's iconic winter dish. Amazake (甘酒 — sweet sake) in one form is made by dissolving sake kasu in hot water with sugar (distinct from the koji-amazake of sweet fermented rice). Sakekasu is also a cosmetic ingredient, used in facial preparations for skin brightening attributed to alpha-hydroxy acids from fermentation. Nada and Fushimi sake breweries produce the most sought-after sake kasu in January–March, during peak pressing season.
Sake kasu contributes: a subtle fermented-grain sweetness, alcohol warmth, amino acid depth, and enzyme-driven tenderisation — simultaneously preserving and flavouring whatever it touches
{"Kasuzuke base ratio: 500g sake kasu + 100g salt + 50g sugar + 3 tbsp mirin, blended to smooth paste; marinate fish 24–48 hours, vegetables 3–7 days minimum","Enzyme tenderisation: the protease enzymes in sake kasu break down surface proteins — fish marinated in kasuzuke will have a distinctly different mouthfeel (silkier) at the flesh surface after adequate marination","Kasujiru preparation: dissolve 2 tbsp sake kasu per 400ml dashi by whisking with warm dashi before adding to soup — add after miso to prevent enzyme deactivation by boiling","Amazake-from-kasu: whisk 100g sake kasu with 400ml boiling water; add sugar to taste; this creates a warming winter beverage distinct from koji-amazake in sweetness source and flavour","Peak season sourcing: sake kasu is available fresh from sake breweries January–April (pressing season); summer kasu is dried (plate kasu or bale kasu) with reduced enzymatic activity"}
{"Kasu-glazed salmon (sake no kasuzuke): arguably the best single use of sake kasu — marinate salmon fillet 24 hours, scrape clean, grill at 200°C 8 minutes; the resulting caramelisation has no parallel","Sake kasu pasta sauce: dissolve sake kasu in cream, add pasta, finish with parmesan — a cross-cultural fermented dairy application that works with surprising elegance","Kasu sourcing from breweries: many Japanese sake breweries sell fresh kasu directly at the brewery gate January–March — the freshest kasu has highest enzymatic activity and fullest flavour"}
{"Boiling kasujiru after adding sake kasu — high heat deactivates beneficial enzymes and the alcohol volatilises abruptly, creating a harsh note; add kasu last and heat gently","Using summer dried kasu (itakasu) without rehydration for pickles — dried kasu needs 30 minutes water rehydration before it will function as a pickle marinade","Over-marinating fish in kasuzuke — 48 hours maximum for most fish; beyond this the enzymes over-tenderise surface flesh to mush"}
Japanese Farm Food — Nancy Singleton Hachisu / Washoku — Elizabeth Andoh