What Standard Governs Palm oil testing in China?
Palm oil testing in China is governed by GB/T 15680-2009 Palm Oil (replacing GB 15680-1995 and GB/T 18008-1999), which covers crude and refined palm oil and its fractionated products — palm olein (棕榈液油), palm super olein (棕榈超级液油), and palm stearin (棕榈硬脂). Each product type carries its own quality-grade table. The standard specifies acid value, peroxide value, melting point (slip), colour, moisture and volatiles, iodine value, and fatty-acid composition, and invokes the GB/T method standards for each.
The food-safety baseline is GB 2716-2018 National food safety Standard for Vegetable Oil, the mandatory hygiene standard covering acid value, peroxide value, solvent residue, heavy metals, aflatoxin B₁, and contaminants — applicable to every edible palm oil sold in China regardless of grade. A further mandatory overlay is GB 2762-2022 Contaminant Limits in Foods, which sets the 3-MCPD limit and is increasingly relevant to refined palm oil because 3-MCPD ester contamination is highest in palm oil among all refined vegetable oils.
The international references are the MPOB (Malaysian Palm Oil Board) test methods — the industry-standard methods developed by the world's largest palm oil research body — and the AOCS (American Oil Chemists' Society) methods, which are cross-referenced with MPOB in laboratory proficiency programmes. The Codex Alimentarius standard CXS 210-1999 (named vegetable oils) and the CXC 79-2019 code of practice for reducing 3-MCPD esters in refined oils provide the international trade reference.
What Is DOBI and Why Is It the Palm-Oil-Specific Test?
The Deterioration of Bleachability Index (DOBI) is the quality parameter unique to crude palm oil — it exists in no other oil's test panel because no other oil has the combination of high carotene content and the need for bleaching that defines crude palm oil processing.
What it measures: DOBI indicates the ratio of carotene content (which bleaching must remove) to secondary oxidation products (which bleaching also must remove but which indicate the fruit was over-ripe or mishandled before processing). A high DOBI means the oil has high carotene and low oxidation — it will bleach easily to a light colour with minimal bleaching earth. A low DOBI means the oil is oxidised and contaminated — it will be difficult to bleach and will require more bleaching earth, raising refining cost and oil loss.
Test method (ISO 17932 / MPOB p2.2): the palm oil sample is dissolved in isooctane (or hexane), and the absorbance is measured at two wavelengths: 446 nm (carotene absorption peak) and 269 nm (oxidation-products absorption). DOBI is the ratio:
DOBI = A₄₄₆ / A₂₆₉
A higher ratio means more carotene relative to oxidation = better quality. The grading scale:
| DOBI value | Grade |
|---|---|
| < 1.8 | Sludge (unfit for normal refining) |
| 1.8 – 2.3 | Poor |
| 2.3 – 2.9 | Fair |
| 2.9 – 3.2 | Good |
| > 3.2 | Excellent |
Carotene content is measured alongside DOBI using the same spectrophotometric method — carotene = 383 × A₄₄₆ × V / W × 100, where V is the solvent volume and W is the sample weight. Crude palm oil typically contains 500–1000 ppm carotene (it is the richest natural plant source of β-carotene), which gives crude palm oil its characteristic deep red-orange colour. The carotene is destroyed in refining (bleaching + deodorising at high temperature), producing the pale refined palm oil of commerce.
The DOBI is the palm-oil-refiner's first quality screen — it tells the refiner how much bleaching earth to dose and whether the batch is worth refining at all. A DOBI below 1.8 indicates the crude oil is from over-ripe, bruised, or delayed-processed fruit, and the resulting refined oil will have poor colour stability and higher refining losses.
What Is the 3-MCPD Ester Contamination Issue?
3-MCPD esters (3--monochloropropanediol fatty-acid esters) are process contaminants formed during high-temperature refining of edible oils — and palm oil is the most affected of all vegetable oils. This is the food-safety issue that has driven the most regulatory and analytical activity in the palm oil sector over the past decade.
How they form: during the deodorisation step of refining (typically ≥200 °C), organic chloride compounds present in the crude oil (from water, fertilisers, pesticides, soil — the plantation and mill environment) react with the oil's triacylglycerides to form 3-MCPD esters. The chloride precursor is the controlling variable — the linear dependence between chloride ion concentration in palm oil and 3-MCPD ester formation is documented. Palm oil's high partial acylglycerol content (diglycerides from enzymatic lipolysis in the fruit) also contributes — diglycerides are more reactive precursors than triacylglycerides.
Health risk: 3-MCPD is a potential human carcinogen. The WHO has set a tolerable daily intake (TDI) of 2 µg/kg body weight for 3-MCPD. In the human digestive tract, 3-MCPD esters are hydrolysed back to free 3-MCPD, which is the active toxicant. Food producers increasingly demand palm oil with 3-MCPD ester content below 2 ppm, and infant-formula manufacturers (who use palm oil as a major ingredient) drive the tightest specifications.
Detection method: the Chinese standard GB 5009.191-2024 (replacing the 2016 edition, effective August 2024) covers 3-MCPD, 2-MCPD, their fatty-acid esters, and glycidyl esters (GE — a related process contaminant) in foods. The method uses alkaline transesterification to release free 3-MCPD from its esterified form, followed by derivatisation and GC-MS or GC-MS/MS quantification. The MS/MS method (new in the 2024 revision) provides higher selectivity and lower detection limits, which matters for the tight specifications on infant-formula-grade palm oil. Internationally, the AOCS Cd 29a-13 and ISO 18363 series are the reference methods.
The chloride-precursor screen (ASTM D4929): because 3-MCPD ester formation correlates with organic chloride in the crude oil, the most cost-effective upstream control is to measure organic chloride in the crude palm oil before refining. ASTM D4929 (and the equivalent UOP 779) quantifies organic chloride by oxidative microcoulometry — the crude oil sample is combusted, the chloride is converted to HCl, and the chloride is titrated coulometrically. A crude palm oil with low organic chloride will produce low 3-MCPD esters in refining; one with high organic chloride will exceed the specification regardless of refining conditions.
What Are the Quality Parameters for Refined Palm Oil?
The quality block for refined palm oil under GB/T 15680 covers the parameters that define whether the oil is fresh, properly refined, and suitable for its intended food use. The headline parameters:
Acid value / free fatty acids (FFA, 酸价): measured per GB/T 5530. For refined palm oil, FFA must be low — typically ≤ 0.20 % (as palmitic acid) for a well-refined product. A high FFA in refined oil indicates either insufficient neutralisation in refining or hydrolytic degradation in storage. For crude palm oil, FFA is the primary quality-grade discriminator — the MPOB grading of crude palm oil sets FFA ceilings by grade.
Peroxide value (PV, 过氧化值): measured per GB/T 5538. PV measures primary oxidation — the hydroperoxides that are the first-stage products of lipid oxidation. Refined palm oil should show a low PV (typically ≤ 10 meq/kg). Palm oil's high saturation (predominantly palmitic and oleic acids) makes it more oxidation-stable than polyunsaturated oils, which is why palm oil is specified for frying applications and long-shelf-life products. A PV that climbs in storage is the early-warning signal for rancidity.
Iodine value (IV, 碘值): measured per AOCS Cd 1d-92 or GB/T 5532. IV measures the unsaturation of the oil — for palm oil, the typical range is 50–55 g/100 g, reflecting the ~40 % oleic acid (C18:1) and ~10 % linoleic acid (C18:2) content. IV distinguishes palm oil from palm olein (IV ~56–61, more unsaturated, liquid at lower temperature) and palm stearin (IV ~30–40, more saturated, solid). An IV outside the expected range indicates either misidentification of the product or adulteration with another oil.
Slip melting point (滑动熔点): measured per ISO 6321 or MPOB P4.2. Palm oil's slip melting point is ~33–39 °C — just above body temperature, which is why palm oil is semi-solid at room temperature. Palm olein has a lower slip point (~19–24 °C, liquid at cool room temperature); palm stearin has a higher slip point (~44–56 °C). The slip point is a primary classification parameter for fractionated products and a key parameter for food formulators.
Solid fat content (SFC, 固脂含量): measured by pulsed NMR per AOCS Cd 16b-93. SFC defines the proportion of solid fat at defined temperatures (10, 20, 30, 35, 40 °C) and is the parameter that food formulators use to design margarine, shortening, and confectionery coatings. The SFC profile distinguishes palm oil from its fractions and is the reason palm oil and palm stearin are specified for specific food applications where a defined solid-fat structure is needed.
Colour (Lovibond, 罗维朋色泽): measured per MPOB P4.1 or AOCS Cc 13e-92. Refined palm oil is pale (low Lovibond red/yellow); crude palm oil is deep red-orange from carotene. The colour specification confirms the bleaching step was adequate. A high colour in refined oil indicates under-bleaching or colour reversion during storage.
How Does Fractionation Affect the Test Panel?
Palm oil is unique among major vegetable oils in being routinely fractionated — split by controlled crystallisation and filtration into a liquid olein fraction and a solid stearin fraction, each with different physical properties and food applications. The fractionated products are distinct products with their own GB/T 15680 specification tables.
| Product | IV (g/100 g) | Slip MP (°C) | Application |
|---|---|---|---|
| Palm oil | 50–55 | 33–39 | Frying oil, general-purpose |
| Palm olein | 56–61 | 19–24 | Cooking oil (liquid at cool temperature), frying |
| Palm super olein | > 62 | < 19 | Cold-climate cooking oil, salad oil |
| Palm stearin | 30–40 | 44–56 | Margarine hardstock, shortening, CB substitute |
The fractionation changes the fatty-acid composition (olein concentrates the unsaturated acids; stearin concentrates the saturated acids), the IV, the slip melting point, and the SFC profile. A test report that does not identify the product type (palm oil vs palm olein vs palm stearin) is not interpretable — the same parameter values mean different things for different fractions.
The fatty-acid composition test (GB 5009.168, by GC-FAME) confirms the product identity. Palm oil's distinctive profile — ~44 % palmitic acid (C16:0), ~40 % oleic acid (C18:1), ~5 % stearic acid (C18:0), ~10 % linoleic acid (C18:2) — is the fingerprint that distinguishes it from other oils. A palm oil adulterated with a cheaper oil (soybean, rapeseed) shows a shift in the palmitic/oleic ratio and the appearance of linolenic acid (C18:3), which is near-zero in pure palm oil.
How Does the GB Framework Map to International Palm Oil Standards?
| Scope | China (GB/T) | International (MPOB / AOCS / ISO) |
|---|---|---|
| Product standard | GB/T 15680-2009 | Codex CXS 210-1999, MPOB specifications |
| FFA | GB/T 5530 | MPOB P2.5 / AOCS Ca 5a-40 |
| Peroxide value | GB/T 5538 | AOCS Cd 8b-90 / ISO 3960 |
| Iodine value | GB/T 5532 | AOCS Cd 1d-92 / ISO 3961 |
| Slip melting point | ISO 6321 (invoked) | MPOB P4.2 / AOCS Cc 3-25 |
| DOBI | ISO 17932 (invoked) | MPOB p2.2 / ISO 17932 |
| Solid fat content | AOCS Cd 16b-93 (invoked) | AOCS Cd 16b-93 / ISO 8292 |
| 3-MCPD esters | GB 5009.191-2024 | AOCS Cd 29a-13 / ISO 18363 |
| Organic chloride (precursor) | — | ASTM D4929 / UOP 779 |
| Colour (Lovibond) | — | MPOB P4.1 / AOCS Cc 13e-92 |
The Chinese standard (GB/T 15680) is closely aligned with the MPOB/Codex framework because palm oil is overwhelmingly an imported commodity in China — the major suppliers (Indonesia, Malaysia) test to MPOB/Codex, and the Chinese standard invokes the same methods (ISO 6321 for slip point, ISO 17932 for DOBI). The differences are in the grade definitions and the specific acceptance thresholds for each fraction, which a Chinese-market report must cite explicitly.
Our Testing Capabilities
Beijing ZKGX Research provides palm oil testing against GB/T 15680-2009, the GB 2716-2018 food-safety baseline, and the MPOB / AOCS / ISO reference framework.
Quality (GB/T 15680):
- Acid value / FFA (GB/T 5530)
- Peroxide value (GB/T 5538)
- Iodine value (GB/T 5532 / AOCS Cd 1d-92)
- Slip melting point (ISO 6321 / MPOB P4.2)
- Colour (Lovibond, MPOB P4.1)
- Moisture and volatiles
Palm-oil-specific:
- DOBI (ISO 17932, UV-Vis spectrophotometry)
- Carotene content (UV-Vis, 446 nm)
- Solid fat content (pulsed NMR, AOCS Cd 16b-93)
- Organic chloride precursor (ASTM D4929)
Contaminants and food safety (GB 2716 / GB 2762):
- 3-MCPD esters, 2-MCPD esters, glycidyl esters (GB 5009.191-2024, GC-MS/MS)
- Aflatoxin B₁ (for palm kernel oil from copra-style processing)
- Heavy metals (GB 5009.268)
Identity and authenticity:
- Fatty-acid profile by GC-FAME (GB 5009.168) — full C12–C18:3 breakdown
- Product identification (palm oil / olein / super olein / stearin)
- Adulteration screen (unexpected linolenic acid, IV shift)
If you need a GB/T 15680 product-quality report for palm oil import/release, a DOBI and carotene test for crude palm oil, a 3-MCPD ester compliance test for food-grade or infant-formula-grade palm oil, a fractionated-product identification (olein / stearin), or an adulteration screen — contact our laboratory with the product type (crude / refined / fraction), target grade, destination market, and applicable standard, and we will scope the test plan.
FAQ
What is DOBI and why is it unique to palm oil?
DOBI (Deterioration of Bleachability Index) is the ratio of UV absorbance at 446 nm (carotene) to 269 nm (oxidation products), measured in isooctane solution. It is unique to palm oil because palm oil has both the highest carotene content of any commercial oil (which bleaching must remove) and a refining process where bleaching is critical. DOBI tells the refiner how easily the crude oil will bleach — a DOBI > 3.2 means excellent quality (easy to bleach), < 1.8 means the oil is too oxidised for normal refining. No other oil has this specific quality screen.
Why is 3-MCPD ester testing more critical for palm oil than for other oils?
Because palm oil produces the highest 3-MCPD ester levels during high-temperature refining, due to its organic chloride content (from the plantation environment) and its diglyceride content (from enzymatic lipolysis in the fruit). 3-MCPD esters are potential carcinogens, the WHO TDI is 2 µg/kg body weight, and infant-formula manufacturers (the largest palm-oil-in-food users) demand the tightest specifications. A refined palm oil that passes quality tests (FFA, PV, colour) but fails the 3-MCPD ester ceiling cannot be used in infant formula and may be restricted in other food applications.
How do palm olein and palm stearin differ in testing?
They are fractionated products — palm olein is the liquid fraction (IV 56–61, slip point 19–24 °C, used as cooking oil), palm stearin is the solid fraction (IV 30–40, slip point 44–56 °C, used in margarine and shortening). The test panel is the same, but the acceptance thresholds differ: olein has higher IV, lower slip point, lower SFC; stearin has lower IV, higher slip point, higher SFC. A test report must identify the fraction, because the same parameter value means different things for different fractions.
Can fatty-acid composition detect palm oil adulteration?
Yes, in most cases. Palm oil's distinctive profile — ~44 % palmitic acid (C16:0), ~40 % oleic acid (C18:1), near-zero linolenic acid (C18:3) — is the fingerprint. Adulteration with soybean oil raises linolenic acid (C18:3) above the palm oil floor; adulteration with rapeseed oil raises erucic acid (C22:1); adulteration with a cheaper palm fraction (e.g. selling stearin as olein) shifts the IV and slip point out of spec. The GC-FAME profile (GB 5009.168) catches all of these.
Is organic chloride testing useful as a preventive screen?
Yes — because 3-MCPD ester formation in refining correlates linearly with organic chloride in the crude oil, the most cost-effective upstream control is to measure organic chloride before refining (ASTM D4929). A crude palm oil with low organic chloride will produce low 3-MCPD esters in refining; one with high organic chloride will exceed the specification regardless of how the refining is run. For a refinery sourcing crude palm oil from multiple plantations, the chloride screen is the tool that identifies which batches need the low-temperature, low-3-MCPD refining protocol.