Iyengar Flavor Index (IFI)
The Iyengar Flavor Index (IFI) is a multi-axis flavor metric that normalizes compound activation against the saturation response of each receptor system, rather than reporting raw chemical concentrations. An IFI-H score of 50 means the construct activates TRPV1 at 50% of its maximum — the same normalization applies to all eight axes, making them directly comparable.
The Eight Axes
IFI-H (Heat, TRPV1), IFI-P (Sharp/Pungent, TRPA1), IFI-C (Cooling, TRPM8), IFI-S (Sweetness, TAS1R2/3), IFI-U (Umami, mGluR1), IFI-B (Bitter Attenuation, TAS2R38), IFI-K (Kokumi, CaSR), IFI-A (Astringency, salivary protein precipitation). Each is independently scored on a 0–100 scale where 100 equals receptor saturation.
IFI-F: Full Composite
IFC (Integrated Flavor Construct) products are additionally scored on IFI-F, a weighted composite of all eight axes that represents total sensory impact. This enables direct comparison of multi-axis constructs that engineer several flavor dimensions simultaneously.
Why Not Just SHU
SHU measures concentration, not receptor activation. Two constructs at the same SHU may have different capsaicinoid profiles — one dominated by fast-onset capsaicin, one by slow, persistent dihydrocapsaicin. IFI-H captures this by measuring the actual TRPV1 response curve. The same logic applies to every axis: IFI scores are predictions of perception, not proxies for concentration.