Overview
ISO 17932:2011 specifies a standardized spectrophotometric method for assessing two quality attributes of palm oil:
- the deterioration of bleachability index (DOBI) of crude palm oil, and
- the carotene content (expressed as β‑carotene) of crude or bleached palm oil and their fractions.
The method uses ultraviolet–visible (UV‑VIS) spectrophotometry on solutions of oil in isooctane, measuring absorbance in a 10 mm (1 cm) quartz cell. DOBI is the ratio of absorbance at 446 nm to that at 269 nm; carotene content is calculated from absorbance at 446 nm and reported in mg/kg.
Key topics and technical requirements
- Scope and principle: spectrophotometric determination of DOBI and β‑carotene in palm oil samples (crude or bleached).
- Sample preparation: homogenize, melt (60–70 °C), filter if necessary and dissolve a weighed test portion in isooctane to obtain absorbances typically between 0.2 and 0.8.
- Instrumentation: UV‑VIS spectrometer capable of measurements at 269 nm and 446 nm using matched quartz cells (10 mm pathlength); wavelength and absorbance scales should be checked (holmium oxide filters, absorbance standards).
- Solvent: isooctane (2,2,4‑trimethylpentane) meeting specified absorbance limits.
- Calculations and reporting:
- DOBI = A446 / A269, expressed to one decimal place.
- Carotene (as β‑carotene) calculated from ΔA at 446 nm, pathlength and concentration and reported in mg/kg (nearest whole number).
- Quality and precision: precision evaluated via interlaboratory studies (repeatability and reproducibility limits provided in Annexes A and B).
- Safety and conformity: use analytical‑grade reagents; follow ISO/IEC 17025 and ISO Guide 34 where applicable.
Applications and users
ISO 17932:2011 is used by:
- Quality control and analytical laboratories testing palm oil raw materials and refined products.
- Palm oil refiners and processors to assess ease of bleaching and refineability (DOBI indicates refining difficulty and potential colour removal performance).
- Regulatory bodies, certification schemes and research institutions monitoring carotene (nutritional and colorant) levels.
- Suppliers and traders for specification compliance and lot acceptance.
Practical benefits include standardized, reproducible data for process control, purchasing specifications, and shelf‑quality assessment.
Related standards
- ISO 661 (sample preparation), ISO 5555 (sampling), ISO 1042 (volumetric flasks)
- ISO/IEC 17025, ISO Guide 34 (laboratory and reference material competence)
- ISO 5725‑1/2 (precision evaluation) and national methods (e.g., MPOB, MS 817, BS 684)
Open preview (PDF)Palm oil — Determination of the deterioration of bleachability index (DOBI) and carotene content