ISO 23293:2020 pdf download.Milk-based infant formula powders — Quantification of whey protein content by sodium dodecyl sulfate-capillary gel electrophoresis (SDS-CGE)
1 Scope
This document specifies a method for the determination of the whey to casein protein ratio, ranging from 20:80 to 80:20 in cow milk-based infant formula powders.
This method does not apply to the analysis of infant formulas containing hydrolysed protein or proteins from other sources (e.g. plants or milk from other mammals).
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1 infant formula
breast-milk substitute specially manufactured to satisfy, by itself, the nutritional requirements of infants during the first months of life up to the introduction of appropriate complementary feeding [SOURCE: Codex Standard 72-1981]
4 Principle
In sodium dodecyl sulfate-capillary gel electrophoresis (SDS-CGE), proteins in infant formula samples are denatured by the anionic surfactant SDS and reduced by β-mercaptoethanol. The SDS-bonded, electrically charged proteins migrate in an electrical field filled with a separation gel and are detected by UV at 220 nm. Caseins and whey proteins are separated as two distinct, non-overlapping groups of peaks where the ratio can be established based on integrated areas without the need for a calibration curve. In the calculation of whey protein content, 1,4 was used as the mass-to-area correction factor for whey proteins versus caseins.
5 Reagents and materials
During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and distilled or demineralized water or water of equivalent purity.
Data from the multi-laboratory study was obtained with chemicals from the SDS-MW kit 390953 from Beckman Coulter/Sciex 1) . The SDS-MW gel separation buffer recipe described below (5.1) was tested in a separate study and found to be equivalent to the commercial SDS-MW gel separation buffer included in the kit. One laboratory used home-made reagents (5.2 to 5.5). All laboratories used the 10 kDa internal protein standard (5.6) and the SDS-MW size standard (5.7) from the kit. Use of equivalent standards requires prior verification.
6 Apparatus
Usual laboratory glassware and equipment and, in particular, the following.
6.1 Capillary electrophoresis instrument, equipped with UV detector set at 220 nm and capable of maintaining the capillary and sample tray at 25 °C ± 2 °C.
Suitable software should be available for peak integration.
6.2 Bare, fused-silica capillaries, of 50 μm internal diameter × 30 cm, with effective length of 20 cm.
6.3 Temperature controlled water bath or heating block, capable of maintaining a temperature of 95 °C ± 5 °C.
ISO 23293:2020 pdf download
