Overview
ISO 11292:1995 specifies a laboratory method for the determination of free and total carbohydrate contents in instant coffee using high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD). The standard covers sample preparation (both direct extraction and strong acid hydrolysis), chromatographic separation, identification and quantification of individual monosaccharides, sucrose and mannitol, and reporting of results on a dry-matter basis.
Key topics and technical requirements
- Analytes specified: individual monosaccharides (arabinose, fructose, galactose, glucose, mannose, xylose where applicable), sucrose, and mannitol - reported as free (method A) or total after hydrolysis (method B).
- Analytical principle:
- Method A: dissolution of sample, filtration and direct HPAEC separation using demineralized water as eluent; detection by PAD.
- Method B: strong hydrolysis with 1.00 mol/L hydrochloric acid, followed by HPAEC analysis to determine total carbohydrate content.
- Chromatography setup:
- High-performance anion-exchange column (pellicular polystyrene-divinylbenzene resin) with guard column.
- Degassed demineralized water and NaOH (≈300 mmol/L) used as eluents; post-column NaOH addition and PAD with gold electrode.
- Typical operating parameters provided (e.g., injection 20 µL, flowrate 1.0 mL/min) and guidance on column conditioning and equilibration.
- Sample preparation: precise weighing, dissolution or hydrolysis, filtration through 0.2 µm membranes and use of disposable cartridges/Cl8 cleanup where recommended.
- Precision & performance:
- Precision depends on concentration and matrix. For carbohydrate contents >0.3% (m/m) repeatability shows ~4.5% relative standard deviation and reproducibility averages ~14.3% (except fructose).
- Annex A summarizes interlaboratory test results used to establish repeatability and reproducibility data.
Applications and who uses it
- Quality control laboratories in coffee manufacturing and instant coffee suppliers - to quantify sugar profiles, verify product specifications and detect adulteration.
- Food testing and R&D labs - to characterize carbohydrate composition for formulation, shelf-life and sensory studies.
- Regulatory and compliance labs - for standardized reporting of carbohydrate contents in product declarations and regulatory submissions.
- Method validation teams and proficiency testing organizers - to evaluate analytical performance and interlaboratory comparability.
Related standards
- ISO 3509 (Coffee vocabulary)
- ISO 3726 (Instant coffee - dry matter determination)
- ISO 1042 (Laboratory glassware)
- ISO 6670 (Sampling instant coffee in cases)
- ISO 5725 (Precision of test methods - repeatability/reproducibility)
Keywords: ISO 11292:1995, instant coffee, HPAEC, carbohydrate analysis, pulsed amperometric detection, monosaccharides, sucrose, mannitol, analytical method.
