Overview
EN ISO 17932:2011 / ISO 17932:2011 defines a spectrophotometric method for assessing two quality parameters of palm oil: the deterioration of bleachability index (DOBI) for crude palm oil and the carotene content of crude or bleached palm oil and their fractions. Published under CEN and ISO, the method uses ultraviolet–visible (UV‑Vis) absorbance measurements to quantify ease of refining (DOBI) and β‑carotene concentration (mg/kg).
Key topics and technical requirements
- Principle: Measure absorbance of an isooctane solution of a homogenized palm oil sample at 446 nm and 269 nm in a 10 mm (1 cm) pathlength quartz cell.
- DOBI calculation: DOBI = A446 / A269 (ratio of absorbance at 446 nm to 269 nm). Results expressed to one decimal place.
- Carotene content: Calculated from ΔA at 446 nm using the formula w_c = 383·ΔA / (l·ρ), giving β‑carotene in mg/kg.
- Solvent and apparatus: Uses isooctane (2,2,4‑trimethylpentane) with specified purity/absorbance limits; requires UV‑Vis spectrometer, matched quartz cells (10 mm), analytical balance, class A volumetric flasks.
- Sample preparation: Melt and homogenize sample (recommended 60–70 °C), filter if necessary, weigh an aliquot (approx. 0.1–0.5 g) into a 25 mL volumetric flask, dissolve in isooctane to obtain A between ~0.2–0.8.
- Instrument checks & safety: Recommends wavelength and absorbance scale checks (e.g., holmium oxide filter, secondary absorbance standards) and compliance with chemical handling regulations (potassium chromate warning).
- Precision and validation: Interlaboratory studies and precision data (repeatability and reproducibility) are reported in annexes; laboratories are expected to follow ISO/IEC 17025 competence requirements.
Applications and users
- Quality control laboratories in palm oil mills, refineries and edible oil processors for assessing refining difficulty and colour/quality.
- Regulatory and standards bodies monitoring carotene content and oil quality.
- Producers, buyers and exporters using DOBI as an indicator of crude palm oil suitability for bleaching and refining.
- Research and analytical labs developing process optimization, shelf‑life studies, or comparative assessments of oil fractions.
Related standards
- ISO 661 - Preparation of test sample (fats and oils)
- ISO/IEC 17025 - Laboratory competence
- ISO Guide 34 - Reference material producers
- ISO 5555 - Recommended sampling methods
- ISO 5725 - Precision of measurement methods (interlaboratory testing)
EN ISO 17932:2011 is an authoritative, reproducible method for routine palm oil testing, integrating clear instrument and sample requirements to support consistent DOBI and carotene determinations.
