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Single Lab Validation Report for GOS in Infant Formula and Adult Nutritionals
13
5
Appendices
5.1
Detailed Method Description
Determination of trans-galacto-oligosaccharides in infant, adult and pediatric
formula
Ion-Exchange Chromatography
Principle:
Galacto-oligosaccharides (GOS) also known as oligogalactosyllactose, oligogalactose, or transgalacto-
oligosaccharides is produced by transgalactosylation of lactose. This method has been set up to
determine the GOS content in infant, adult and pediatric formula.
Currently, the standard method for analyzing GOS in food products is AOAC 2001.02 (De Slegte, 2002).
GOS and lactose in the sample are hydrolyzed with an enzyme to galactose and glucose. GOS content is
calculated from the difference in galactose content of a hydrolyzed and non-hydrolyzed sample.
The disadvantage of the AOAC 2001.02 method for IFT is that the high lactose content in IFT results in a
high quantity of galactose formed after hydrolysis. The resulting galactose quantity is very high
compared to the galactose quantity released from GOS. For the GOS calculation two large numbers are
subtracted, which leads to an estimate for GOS content that is not precise. Precipitation with cold
ethanol can be applied to remove part of the lactose. However, a considerable amount of lactose
remains and part of GOS may be removed as well.
In the currently proposed method, which is developed in collaboration with Danone Nutricia Research,
lactose is removed with a chromatographic preparative step before hydrolysis. The method consists of
the following steps:
1) preparative separation
2) SPE purification and concentration
3) enzymatic hydrolysis
4) HPAEC-PAD analysis
The GOS concentration is expressed as g GOS in 100 g reconstituted product.
GOS-02 SLV
FOR ERP USE ONLY
DO NOT DISTRIBUTE