Ney Q-rule
concept / concept-q-rule
Qルール
Ney Q-rule is an empirical rule (Ney 1971) predicting bitterness in peptides with average hydrophobicity Q above 1400 cal/mol and molecular weight below about 6000. Later research questions its generality.
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Reading the bitterness
The Q rule is an empirical attempt to predict whether a peptide tastes bitter from its amino-acid composition alone; it is attributed to Ney in 1971. It predicts bitterness for peptides with average hydrophobicity Q, a measure of water avoidance, above 1400 cal/mol and molecular weights of approximately 100–6000. However, only the bibliographic record of Ney's original paper has been checked for this database; the rule's content is based on its description in a citing 2008 paper.
Studies differ on how well the rule holds. A fractionation study of 2 commercial soy-protein hydrolysates stated that Q-based hydrophobicity did not support the Q rule as a predictor of bitterness. The relationship with molecular weight was not simply one-directional: bitterness peaked in fractions near 4000 or 2000, whereas fractions below 1000 were least bitter. In another study of 3 synthetic dipeptides, Gly-Phe, Gly-Leu, and Gly-Gly, the 2 more hydrophobic ones were bitter and activated hTAS2R1, whereas less hydrophobic Gly-Gly was tasteless and did not activate the receptor. This agreed with the Q rule within that range, but confirmation in only 3 dipeptides does not test the rule's generality.
A separate 2024 review quotes Ney's original formulation more fully, giving boundaries below 1300 cal/mol for non-bitter peptides and above 1400 cal/mol for bitter peptides. The range from 1300 to 1400 is not specified in the review's quotation.
A study of peptides from shrimp-head autolysate, discussed in another review, found the opposite of the Q rule's prediction: a fraction with lower average hydrophobicity had a higher bitterness score. The review says bitter components were concentrated in the 3–5 kDa fraction, and that hydrophobic amino-acid residues toward the C terminus contributed more to bitterness than those toward the N terminus.
Sources for this overview
Bitter peptides activate hTAS2Rs, the human bitter receptors
Checked for this overview: Checked the Q-rule definition and that only bibliographic information was checked for Ney's original paper. / Checked results agreeing with the Q rule for 3 synthetic dipeptides.
Hydrophobicity of bitter peptides from soy protein hydrolysates
Checked for this overview: Checked the result that the Q rule did not predict bitterness for soy peptides.
Research on Bitter Peptides in the Field of Bioinformatics: A Comprehensive Review
Checked for this overview: The 1300/1400 thresholds in Ney's original Q-rule description.
Checked for this overview: An example in shrimp peptides in which hydrophobicity and bitterness related in the opposite direction.
Structured claims — open a section to read each claim's confidence, evidence and limits
Sensory (3)
Scope: Peptides. A prediction based solely on amino acid composition.
Note: Not supported in soy protein hydrolysates (Cho 2004, see contradicts). There is also a report of consistency at the dipeptide level (Maehashi 2008). The original Ney 1971 source was checked for bibliographic metadata only (metadata_only); the statement of the rule relies on a quotation in the full text of Maehashi 2008.
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concept-q-rule —predicts_bitterness_from_mean_hydrophobicity→ "A peptide with mean hydrophobicity Q > 1400 cal/mol and a molecular weight in the range of about 100-6000 is bitter (Ney's 1971 empirical rule)."Scope: Layer: literature. A statement in a 2024 review that cites the original Ney 1971 source.
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concept-q-rule —is_defined_as→ "In Ney's (1971) original statement of the Q-value rule (Ney's rule), a peptide with a Q-value below 1300 cal/mol is not bitter and a peptide above 1400 cal/mol is bitter; the range of 1300-1400 is not specified."Scope: Layer: literature (secondary citation). A study of shrimp-head autolysate peptides by Fu et al. (original not read), as summarized by the Wang et al. 2026 review.
Note: Secondary citation. The original (Fu et al.) was not checked; this is based on the summary statement in Section 2.1 of Wang et al. 2026 (Foods, full text checked).
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concept-q-rule —does_not_predict→ "A study examining peptides derived from the autolysis products of shrimp heads reports that the fraction with lower mean hydrophobicity showed, conversely, stronger bitterness; the bitter components were concentrated in the 3-5 kDa molecular weight fraction; and hydrophobic amino acid residues at the C-terminus contributed more strongly to bitterness than those at the N-terminus."