aku-nuki (blanch-and-soak treatment)
process / process-aku-nuki
あく抜き（茹でこぼし・水さらし）
Aku-nuki (blanch-and-soak treatment) is a group of Japanese preparation methods, such as boiling and discarding the water or soaking, that make wild vegetables and strongly flavored greens easier to eat. The target differs by ingredient; bitterness, egumi, and specific water-soluble compounds are not treated as the same thing.
On this page (7 sections)
Reading the bitterness
Aku-nuki is an umbrella term for Japanese preparation methods, such as boiling and discarding the water or soaking, that make wild vegetables and strongly flavored greens easier to eat. What these methods seek to reduce varies by ingredient; bitterness, egumi, and particular water-soluble compounds cannot be grouped as a single target. Public information from Japan's Ministry of Agriculture, Forestry and Fisheries says that traditional boiling and soaking can substantially reduce pyrrolizidine alkaloids in fuki and fukinoto, because these compounds are water-soluble. The same source says that, with this preparation, health concerns are not anticipated unless large amounts are consumed continuously. However, that page gives no numerical estimate of reduction, and a follow-up presentation believed to contain figures could not be checked.
For an actual cooking record, the Shimane regional dish 「ふきのとう味噌」 (fukinoto miso) calls for boiling fukinoto in hot water with salt and baking soda, soaking it in water for a while to remove egumi, then squeezing, chopping, and mixing it with miso. Yamagata warabi is also documented as used after aku removal in tataki, ohitashi, simmered dishes, miso soup, and the like. Both describe cooking practices that are actually used; neither gives quantitative values for which components decline or by how much.
Sources for this overview
Checked for this overview: Checked the statement that boiling and soaking reduce pyrrolizidine alkaloid content.
Checked for this overview: Checked the Shimane fukinoto miso steps of boiling with salt and baking soda, then soaking.
Checked for this overview: Checked the Yamagata warabi record for uses after aku removal.
Follow the connections
aku-nuki (blanch-and-soak treatment) →reduces→ pyrrolizidine alkaloids
fukinoto (butterbur flower bud) →is prepared through→ aku-nuki (blanch-and-soak treatment)
warabi (bracken) →is prepared through→ aku-nuki (blanch-and-soak treatment)
Hypotheses and recipe candidates for this entry are on the Japanese page.
Structured claims — open a section to read each claim's confidence, evidence and limits
How processing and cooking change it (4)
Scope: Fuki and fukinoto. Public information from MAFF based on a survey of PA in foods
Note: Explained as due to the water-soluble nature of PAs. The reduction rate is not given as a number on the information page, and the press release for the 2nd-report content survey that carried the figures could not be retrieved (403).
Show data
process-aku-nuki —reduces→ compound-pyrrolizidine-alkaloidsScope: The Shimane fukinoto-miso recipe in MAFF's "Uchi no Kyodo Ryori" (Our Local Cuisine) database
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ingredient-fukinoto —is_prepared_with→ process-aku-nukiScope: A public local-cuisine record on warabi from Yamagata Prefecture
Note: A recorded cooking practice; it does not give a reduction rate for any specific compound or for bitterness from aku removal.
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ingredient-warabi —is_prepared_with→ process-aku-nukiScope: The preparation method in a local-cuisine record from Toyama Prefecture
Note: A parboiling method using rice bran and red chili pepper, different from the baking-soda aku removal for fukinoto (recorded elsewhere).
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dish-takenoko-misoni-toyama —is_prepared_with→ process-aku-nukiCulture (1)
Scope: Layer: literature. The closing statement of a 1980 review of Japanese culinary science (an overview of bitter compounds in food).
Note: A record in which the researcher themselves, as of 1980, wrote about the gap in research directly measuring the relationship between aku removal, other pretreatment, and bitterness.
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process-aku-nuki —is_documented_as_having→ "The closing words of a 1980 review: "Research on the formation of bitter compounds contained in plant-based foods, and on its prevention, still has much left for the future. In addition, research on how these bitter compounds change through cooking has hardly been carried out.""