日本語版

Topic hubs

The encyclopedia builds evidence one entry at a time; the research notes follow one question each. A topic hub sits between them: it answers the first question, then leads to the related entries, notes, and sources. These are the hubs available in English.

• What Is IBU? Beer Bitterness Units vs. the TasteIBU (International Bitterness Units) is an absorbance measurement, not the bitterness you actually taste. Iso-α-acids from hops, IBU rising while iso-α-acids fall with dry hopping, and how storage changes the quality of bitterness — a topic hub gathering what IBU measures and what it misses, built from the encyclopedia's claim data.
• The Words for BitternessDo dictionaries across languages define bitterness as the same taste, and does it carry the same value? A topic hub gathering, with sources, how dictionaries phrase their definitions, how the word extends into metaphor, its etymology, and documented confusions of taste, built from the encyclopedia's claim data.
• Bitter gourd's bitternessThe identity of the compound behind bitter gourd's bitterness has been reassigned differently by a 1982 study and a 2024 study. Salt-water soaking left bitterness unmoved, while gum arabic and cyclodextrin moved it — a topic hub gathering only the confirmed claims across compound identity, preparation, and maturation.
• Bitterness, Astringency, Egumi, and PungencyA topic hub that separates bitterness, astringency, egumi, and pungency into four layers — a basic taste, an oral touch sensation, a chemesthetic sense, and a Japanese food-sensory word — and, with evidence, extends to the time-axis recording methods huigan and the time-intensity (TI) method.
• Citrus bitternessWhere citrus bitterness comes from, why it arrives late, and how it gets removed. A topic hub gathering, using only confirmed claims, the different roles of limonin and naringin, where it concentrates in the white pith, the ways it's removed — enzymes, resin, salt, high pressure — and how the wording splits between cultivars and product descriptions.
• Tea's bitterness and astringencyWhere is tea's bitterness and astringency decided — in the leaf, the water, or the fire? A topic hub gathering only the claims confirmed at each stage: the carriers catechins and caffeine, shading and picking, water temperature and steeping, and firing and post-fermentation.
• Coffee bitternessWhat coffee's bitterness owes to roasting, and what else moves it. Chlorogenic acid and quinides in the green bean, caffeine's share of the contribution, cultivar and defect beans, brewing and additives — a topic hub gathering only the claims that could be confirmed.
• Herbal Bitters and Amari: BitternessWhere does the bitterness of herbal bitters and amari come from, and how do pharmacopoeias, dictionaries and standards write about it differently? A topic hub gathering the compounds and bitterness values of gentian, cinchona and wormwood, the definitions in EU regulation and food codes, and how differently individual brands talk about their own bitterness.
• Bitter Taste Receptors (TAS2R)Bitter taste receptors (TAS2R) differ compound by compound in the range of substances they respond to, and genotypes such as TAS2R38 explain part, but not all, of the individual variation in bitterness. A topic hub that separates cell-level activation from bitterness as tasted in the mouth, gathering only claims that have been confirmed.
• Sansai and seasonal bitternessOf Japan's sansai (wild spring greens), only fukinoto and yomogi have isolated, named bitter compounds — and one study found those compounds barely transfer into hot water. Whether household aku removal actually moves bitterness has not been measured, and even the origin of the saying 'pile bitterness onto the spring plate' cannot be pinned down in the original text. Ginkgo nuts, akebi peel, edible chrysanthemum and the spring greens of Korea are placed on the same scale. A topic hub that keeps what has been confirmed separate from what is still unmeasured.
• Fermentation and bitter peptidesWhere does fermentation create bitter peptides, and where does it break them down? A topic hub gathering the Q-rule and its counterexamples, cheese's strain-driven creation and removal of bitterness, sake's peptide and amino-acid accounts, and the difference between receptor activation and bitterness felt on the tongue.
• Chicory and radicchio bitterness — what changes it?Treviso's specification pairs a degree word ('slightly') for precoce with an evaluation word ('pleasantly') for tardivo, which cannot be ranked — a topic hub of confirmed claims only.
• Lupin bitterness — what makes lupins bitter or sweet?Lupin bitterness comes from quinolizidine alkaloids (QA). The threshold separating 'bitter' from 'sweet' cultivars differs between EFSA and a 2025 review — a topic hub of confirmed claims only.
• Fenugreek bitterness — same source in seed and leaf?Fenugreek seed bitterness is attributed to saponins like protodioscin as background text; leaf bitterness correlates with diosgenin (r=0.92) in a direct sensory measurement — confirmed claims only.
• Cacao bitterness and astringency — where does it change?Cacao bitterness is not explained by theobromine and caffeine alone. Fermentation raises it at some facilities and lowers it at others, roasting lowers perceived bitterness as temperature rises, and adding fat lowers it without changing the compounds — a topic hub that keeps sample, compound, process and formulation apart.
• When bitterness and harm are the same compoundAmygdalin in almonds and apricot kernels, steroidal glycoalkaloids in potato and tomato. When the compound that carries the bitterness is the compound that matters at higher amounts, what do domestication, ripening and processing actually remove? A topic hub built only from claims that still hold their measurements.
• Getting used to bitternessRepeated exposure raises liking for vegetables and raises adults' pleasantness ratings for a bittersweet drink in seven days. Yet frequent coffee drinkers rate bitterness more intensely. Does getting used to it mean perceiving less, or minding less? A topic hub built only from claims that hold their measurements.
• Handling the bitterness of medicinesClarithromycin dry syrup is estimated to fall to about 1% of the bitterness intensity of a powder suspension, and coated quinine pellets release only 2.1% in five minutes. Yet adding 5% citric acid lowers overall palatability even as it suppresses bitterness. Measuring, masking, and what masking costs.
• Is scorched rice bitter?The crust of rice at the bottom of the pot has a name in many places, and in every language the word comes from scorching. Yet almost every source gathered here speaks of fragrance, not bitterness. Neither the trained panel's scale nor the consumer test's attributes included bitterness at all.
• Mediterranean bitter vegetablesMost of the wild greens recorded on Ikaria are described as bitter, and the production standard for the Sardinian artichoke writes a balance of bitter and sweet into the specification itself. In dandelion, olive leaf, lampascione and white asparagus the carrying compounds have been identified.
• African bitter leavesVernonioside A1, the bitter principle of bitterleaf, produces bitterness from 7 µg and is nearly as strong as quinine sulfate. Yet the endpoint of the washing that removes that bitterness is written only as a desirable level. A hub that places an identified molecule beside a process with no stated endpoint.
• Bitterness in the Andes and MesoamericaCassava is split into sweet and bitter varieties at 100 mg/kg of HCN in the root, and Andean potatoes into papa amarga and papa dulce. Where bitterness names a variety class, the process that removes it grows to 21–30 days in a river. This hub follows that through to what is left.
• Bitterness in Southeast AsiaThai public vegetable guides carry a category called rot khom, bitter taste, with khilek flowers and pheka pods in it. The instructions for removing that bitterness are written not in temperature but in counts: boil and discard at least twice, three to five minutes depending on how bitter you want it.
• Bitterness in offalFoie gras has its veins drawn, liverwurst its bile ducts removed, Tuscan liver paste its gall bladder lifted out unbroken. Meanwhile nam pia uses digestive fluid, niubie adds cattle bile, and the recipe for sa says: if you like it bitter, add bile.

The full list of hubs is on the Japanese page. See also the research notes and the bitter crossings in English.