Overview
ISO 7466:1986 specifies a colorimetric-spectrometric method for the determination of 5-hydroxymethylfurfural (5‑HMF) in fruit and vegetable products produced by thermal processing. The procedure forms a red chromophore by reacting 5‑HMF with p‑toluidine and barbituric acid, and measures absorbance at 550 nm to quantify 5‑HMF. The standard covers sample preparation, reagent recipes, clarification (Carrez treatment), calibration and result expression (mg/L or mg/kg).
Key topics and requirements
- Scope: Applicable to products resulting from thermal processing of fruits and vegetables; results may be reported in mg/L (juices) or mg/kg.
- Principle: Reaction of 5‑HMF with p‑toluidine and barbituric acid produces a red color measured spectrometrically at 550 nm (1 cm pathlength).
- Reagents and solutions:
- p‑toluidine reagent (prepared in propan‑2‑ol with glacial acetic acid).
- Barbituric acid solution (0.500 g in 100 mL water).
- Carrez I and II clarification reagents (potassium hexacyanoferrate(II) and zinc sulfate heptahydrate).
- Acetaldehyde 1% (v/v) for samples containing >10 mg free SO2/L to eliminate interfering SO2.
- 5‑HMF stock and working standards for calibration.
- Sample preparation:
- Homogenize and, if necessary, filter samples; use Carrez clarification and discard first 20 mL filtrate.
- For products with >10 mg free SO2/L, pre‑treat aliquots with acetaldehyde.
- Measurement procedure:
- Add p‑toluidine reagent to aliquots, then add barbituric acid solution to produce the red chromophore.
- Read absorbance at the maximum, typically 3–4 minutes after barbituric acid addition.
- Calibration and calculation:
- Prepare a calibration series from the 5‑HMF working solution (specified microgram levels) and plot absorbance versus micrograms 5‑HMF.
- Compute sample concentration using the calibration and reporting conventions in the standard.
- Practical notes: reagent storage, timing of reading (critical as absorbance falls after peak), and test‑portion sizing for high‑HMF samples.
Applications and users
ISO 7466 is intended for:
- Food testing laboratories performing HMF determination in fruit juices, purees and processed vegetable products.
- Quality control and R&D teams monitoring effects of thermal processing, ageing or storage on product chemistry.
- Regulatory and certification bodies requiring standardized measurement of 5‑HMF for compliance and labeling.
Practical uses include routine QC testing, process optimization to limit thermal degradation, and comparative analysis of product batches.
Related standards
ISO 7466 was prepared by ISO/TC 34 (Agricultural food products). Users commonly combine it with other ISO methods for compositional analysis, clarification procedures and spectrometric measurement practice when developing complete test protocols.
Open preview (PDF)Fruit and vegetable products — Determination of 5-hydroxymethylfurfural (5-HMF) content
