What is the refractive index of shea butter at 40 °C?

Published values for genuine shea butter cluster around 1.463–1.467 at 40 °C. The range is the same for every grade because refractive index is an identity value, not a freshness grade. EMI Agro states the measured refractive index on the Certificate of Analysis.

How does refractive index help detect adulterated shea butter?

Adulterants have a different refractive index: lauric and palm fats typically pull it down; mineral oil typically pushes it up. A value outside the shea range, especially with a matching shift in saponification value and iodine value, indicates a blend or substitution. Refractive index alone is a screen, not proof — confirm with SAP, IV, unsaponifiables and, if needed, a GC fatty-acid profile.

Why is the refractive index of shea butter measured at 40 °C?

Refractive index changes with temperature (about 0.000365 per °C for fats), so a fixed reference temperature is needed. 40 °C is the convention for fats that are solid at room temperature, because they are fully liquid there. Readings at other temperatures are corrected to 40 °C before comparison.

Can refining change the refractive index of shea butter?

Not materially. Refining removes free acids, pigments, odours and peroxides but does not change the triglyceride composition that sets refractive index. That is why an out-of-range refractive index cannot be fixed by refining — the lot is the wrong material.

How is refractive index measured in shea butter?

With an Abbe or digital refractometer at 40.0 °C using a melted, dry, filtered sample, read to four decimal places (ISO 6320 / AOCS Cc 7-25). Water, crystals or an oxidised sample distort the reading. EMI Agro states the measured value and method on the Certificate of Analysis.

What does an out-of-range refractive index mean for shea butter?

It means the material’s composition is not that of pure shea butter — adulteration, a different species or fat, or (rarely) a badly oxidised or polymerised sample. It is not a grade or freshness issue: reject or investigate; do not negotiate on price.

Specifications

Refractive Index of Shea Butter

The identity test: what shea's RI should be at 40 °C, how to measure and correct it, and why a wrong number means the wrong fat — not a bad batch.

Refractive index is the ratio of the speed of light in air to its speed in the fat, measured at a fixed temperature (40 °C for fats such as shea) with the sodium D line — written n_D⁴⁰, then “RI at 40 °C”. Genuine shea butter clusters around 1.463–1.467 at 40 °C. RI depends on composition (unsaturation, chain length, triterpene content), so it is an identity check that storage and refining do not change.

RI at a glance

Unit: n_D at 40 °C (dimensionless)
Test method: ISO 6320 · AOCS Cc 7-25
Literature range: 1.463–1.467 at 40 °C
Same for unrefined and refined: Yes — refining does not materially change RI
Out-of-range means: Adulteration or wrong fat — an identity failure
Temperature correction: ≈ 0.000365 per °C (RI falls as temperature rises)
Control lever: Identity (sourcing and intake screening)

What refractive index measures in a fat

Light bends more in denser, more polarisable liquids. In fats, refractive index rises with unsaturation, with longer average chain length, and with conjugation and oxidation products. Shea's reading is set by its fatty-acid profile (Stearic acid, Oleic acid, Linoleic acid, Palmitic acid, Arachidic acid) and its high unsaponifiable fraction — see unsaponifiable matter.

Because composition is fixed at the tree, refractive index is a fingerprint of the fat, not a record of its handling. Refractive index tells you what the fat is; free fatty acid and peroxide value tell you what has happened to it.

Reference values by grade

Refractive index at 40 °C by shea butter grade — EMI Agro does not publish a standing acceptance range; the batch COA states the measured value
Grade	Valueat 40 °C	What it usually indicates	EMI supply status
Grade A	—	Refractive index is an identity check: a value outside the shea range suggests a different fat or a blend.	Confirm on the batch COA
Grade B	—	Refractive index is an identity check: a value outside the shea range suggests a different fat or a blend.	Confirm on the batch COA
Grade C	—	Refractive index is an identity check: a value outside the shea range suggests a different fat or a blend.	Confirm on the batch COA
Refined N-RBD	—	Refractive index is an identity check: a value outside the shea range suggests a different fat or a blend.	Confirm on the batch COA

Identity parameters are expected to share one range across grades. Published values vary by source; use them to interpret direction of shift, not as pass/fail limits.

EMI Agro does not publish a standing refractive-index range by grade. The value is identity, not quality, so literature figures are the same across grades. Differences versus common adulterants are a few thousandths, so the reading must be careful and read with saponification value and iodine value. A shift toward palm, palm kernel or coconut typically lowers RI; toward mineral oil typically raises it.

Identity reference points — refractive index of shea butter and fats used as adulterants (published values, not EMI limits)
Fat	Refractive index	Temperature
Shea butter	1.463–1.467	40 °C
Cocoa butter	1.456–1.459	40 °C
Palm oil	1.454–1.456	50 °C
Palm kernel oil	1.448–1.452	40 °C
Coconut oil	1.448–1.450	40 °C
Liquid paraffin / mineral oil	≈ 1.473–1.483	20 °C

Never mix 20 / 40 / 50 °C values without correction. See shea versus cocoa butter and shea versus coconut oil for formulation contrasts.

How refractive index is measured (ISO 6320 / AOCS Cc 7-25)

An Abbe or digital refractometer with prism temperature controlled at 40.0 ± 0.1 °C is used. Melt and filter the sample (dry, free of water — droplets blur the boundary); apply a few drops; read to four decimal places; calibrate with a standard.

Temperature correction: R = R′ + K (T′ − T), K ≈ 0.000365 for fats. Worked example: reading 1.4645 at 42.0 °C → 1.4645 + 0.000365 × 2 = 1.4652 at 40 °C.

Shea is solid at 20–25 °C, so 40 °C is the convention for fats. Incomplete melting, moisture, oxidised sample or a few tenths of a degree of drift all move the fourth decimal. See ISO 6320 and the COA interpreter.

Why refractive index matters to buyers

Refractive index is cheap, fast and needs microlitres of sample — the first screen a laboratory runs when a lot arrives. Read alone it is weak (overlaps with cocoa butter); read with saponification value, iodine value and unsaponifiables it is strong.

A refractive index outside the shea range is not a quality defect to negotiate on price — it means the material is not pure shea butter. Grade C with high FFA still has a normal refractive index. What fails: blends, substituted fats, mineral-oil dilution, mislabelled species. Practical signs sit on signs of adulterated shea butter.

An identity failure cannot be refined away

Refining removes free acids, pigments, odours and peroxides; it does not change the triglyceride backbone or remove a blended-in fat or hydrocarbon. Refractive index (and saponification value, iodine value) of an adulterated lot stays out of range after refining. Contrast free fatty acid, which refining can fix — see how shea butter is refined to N-RBD. Adulteration typically enters at aggregation, not at the cooperative; see shea butter grades.

How EMI Agro uses refractive index

EMI Agro states the measured refractive index on the Certificate of Analysis. Identity screening belongs with saponification value and iodine value. See Certifications & Quality and the sample Certificate of Analysis.

Saponification value is the companion identity test. Iodine value rises with refractive index. Unsaponifiable matter raises RI slightly; mineral oil raises both. Melting point tracks the same stearic/oleic ratio.

Shea Butter Specifications

FFA, peroxide value, moisture, refractive index, saponification value and more.

Complete Guide to Shea Butter

Master reference — grades, production, specifications, uses, sourcing, importing.

Shea Butter Grades

Grade A, B and C unrefined shea butter and refined N-RBD explained.

Saponification Value

Saponification value as a chain-length and identity parameter.

Iodine Value

Iodine value as an unsaturation and identity check.

Unsaponifiable Matter

The unsaponifiable fraction that distinguishes shea from cheaper hard fats.

Melting Point

Slip melting point and how it governs shea butter skin feel.

COA Interpreter

Check whether a refractive index sits in the shea band.

Shea Butter vs Cocoa Butter

Identity contrast with cocoa butter.

Shea Butter vs Coconut Oil

Lauric fats pull refractive index down.

Certificate of Analysis (sample)

How a batch is reported.

Frequently asked questions

References & standards

ISO 6320 — Animal and vegetable fats and oils — Determination of refractive index — International Organization for Standardization
AOCS Official Method Cc 7-25 — Refractive Index — American Oil Chemists' Society
Codex Alimentarius CXS 210-1999 — Standard for named vegetable oils — FAO / WHO
Codex Alimentarius CXS 86-1981 — Standard for cocoa butter — FAO / WHO
Honfo, F.G. et al. (2014). Nutritional composition of shea products and chemical properties of shea butter: a review — Critical Reviews in Food Science and Nutrition

Last reviewed September 2026 by EMI Agro Industries QC team.

Manufacturer-direct from Ibadan, Nigeria

Identity you can verify — request the COA.

Every EMI Agro batch is screened for identity at intake and reported on the COA. Tell us your grade and application; we'll send a current Certificate of Analysis with refractive index, SAP and iodine value.

You have just read Refractive Index of Shea Butter. The next step is a real lot from the factory that produces it — EMI Agro, with factory-direct pricing and a batch Certificate of Analysis.

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We ship to European Union, United States, Canada, United Kingdom and Southeast Asia, China, India, Middle East, Latin America. Load ports: Apapa (Lagos) or Tin Can Island (Lagos).
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