Overview
ISO 1743:1982 specifies the refractive index method for determining the dry matter content of glucose syrup. The standard covers measurement on the undiluted product at specified temperatures and calculates dry matter by reading refractive-index-to-composition tables. It is applicable to standard glucose syrups and syrups containing fructose (e.g., HFCS).
Key topics and technical requirements
- Principle: Determine refractive index of an undiluted syrup at a controlled temperature and read the corresponding dry matter (mass %) from ISO 1743 tables.
- Apparatus: An Abbe-type or equivalent refractometer (range ~1.3000–1.5500, resolution ±0.0002) equipped with a thermometer and water-circulation device to maintain measurement temperature.
- Measurement temperatures: Typical controlled temperatures given are 20, 30, 45 and 60 °C (±0.2 °C); the instrument must keep prisms at the selected temperature.
- Sample preparation: Use the product as received; bring sample to measuring temperature before testing.
- Procedure:
- Apply a small quantity (1–3 drops) to the fixed prism using a glass rod (PTFE-covered recommended) and close the movable prism.
- Read refractive index to the nearest 0.0002 and take at least two readings per portion; perform a second determination on a new portion.
- For warmed, viscous samples measurements should be rapid-the application to the prism face should take no more than 2 seconds.
- Repeatability: Two determinations by the same analyst on the same sample (in rapid succession) must not differ by more than 0.2 g dry matter per 100 g of product.
- Tables and corrections: Annex contains refractive-index tables for syrups with various DE (dextrose equivalent) values, ash contents and for HFCS (42%, 55%, 90% fructose). Correction factors for temperature, DE and ash are provided. Values were established using Lane & Eynon methods (see ISO 5377).
Applications and who uses it
- Quality-control laboratories in the food and sweetener industry measuring glucose syrup dry matter content for production, blending and sale.
- Syrup and sweetener manufacturers (corn syrup, high-maltose syrup, HFCS) for process control and specification compliance.
- Ingredient suppliers, R&D labs and regulatory testing bodies that require a standardized, reproducible method for estimating solids concentration from refractive index.
- Useful when viscosity or concentration makes direct weighing difficult - the refractive index method gives a rapid, non-destructive measurement.
Related standards
- ISO 5377 - Starch hydrolysis products: determination of reducing power and dextrose equivalent (method referenced in ISO 1743).
- Manufacturer instructions for specific refractometer models (calibration and illumination).
Keywords: ISO 1743:1982, glucose syrup, dry matter content, refractive index method, refractometer, dextrose equivalent (DE), HFCS, measurement temperature, quality control.
