4-hydroxybenzoic acid

sour acid

Found in 146 ingredients across the CompKitchen flavor graph.

Look up another compound — search by name, CAS number, PubChem CID, or FEMA #.

2D Lewis Structure

Formula: C7H6O3
Molecular weight: 138.12 g/mol
PubChem CID: 135 — full record on PubChem

Properties

Odor description: phenolic, nutty
Odor threshold — in a food matrix: 0.040 ppb – 2.3 ppb median 1.2 ppb · 2 published values · see all 2 with sources
Volatility: high
CAS number: 99-96-7
Retention index: 1558

Not in FEMA GRAS publications 1-33. Of 3,367 listed flavoring substances, none match this compound name. May still be food-safe under other regulatory routes (FDA 21 CFR 172, EFSA, JECFA) — check femaflavor.org for the authoritative current list.

How this molecule is described

Sources disagree about odour more often than they disagree about chemistry. Rather than show one answer, here is every description on file with how many ingredient records carry it.

Also filed as

p-hydroxybenzoic acid

Same molecule, unified here — previously counted and displayed as separate compounds.

Descriptions on file

Ordered by how many independent descriptor streams give each wording, then by how often it appears. The bar is still replication — one source copied onto many ingredients scores high there — so the two can disagree.

solvent FlavorDB 2.0, Flavordb Odor Column 2 sources agree

chemical FlavorDB 2.0, Flavordb Odor Column 2 sources agree

phenolic, nutty shown above FlavorDB 2.0

nutty, phenolic FlavorDB 2.0

acrid, rose, vanilla FlavorDB 2.0

acrid Flavordb Odor Column

—

Bars are the share of ingredient records carrying each description. High agreement means the sources replicate each other — not necessarily that they are right.

Published thresholds

2 measured values from the literature. Grouped by what was actually measured — a threshold smelled in clean water, tasted in the mouth, or measured in a real food are three different quantities and are not pooled.

In a food matrix

0.040 ppb – 2.3 ppb

Measured in a real food, where the matrix shifts detection — not a clean-water value.

Threshold	Matrix	Source	Paper
0.040 ppb	water (food: beer)	Literature corpus	—
2.3 ppb	water (food: unknown)	Literature corpus	—

Only values we can attribute are listed. Where a compendium's licence does not permit public attribution its figures are omitted here, so every number on this page traces to a citable source.

Found in

Measured impact first, then profile share

Every ingredient known to contain 4-hydroxybenzoic acid. Ingredients with a measured concentration come first, ranked by odour activity; the rest follow by how large a share of that ingredient's profile this molecule is. The figure beside each is how many different compounds that ingredient has in total — not the concentration of 4-hydroxybenzoic acid in it.

26 cmpds

63 cmpds

95 cmpds

109 cmpds