Galacto-oligosaccharides (GOS)

Galacto-oligosaccharides are built rather than extracted. Lactose is held in solution and treated with a beta-galactosidase (EC 3.2.1.23) which, instead of simply splitting the disaccharide, transfers galactosyl units onto other lactose molecules. That transgalactosylation gives chains of two to eight sugar units, most carrying a terminal glucose. The linkage pattern follows the enzyme: preparations derived from Bacillus circulans give predominantly beta-(1,4) linked GOS, while those from Kluyveromyces lactis and Aspergillus oryzae give mainly beta-(1,6) types. The enzymes are heat-inactivated as processing aids, and the liquor is then decolourised, demineralised and either concentrated to a syrup or spray dried. Chromatographic removal of residual lactose and monosaccharides is the step that separates the 90% grade from the 57% and 70% commodity grades, and it is where most of the cost sits. The 90% grade assays at 90% GOS minimum on dry matter with lactose at 10% maximum, glucose at 3% and galactose at 1%, moisture at 3.5% maximum and sulphated ash at 0.5% maximum; the 70% grade runs at 70% GOS minimum on dry matter with lactose plus monosaccharides up to 32%. Both sit at pH 2.8 to 6.0 in solution and carry roughly 20 to 40% of the sweetness of sucrose, so fibre can be added without rebuilding the sweetness profile. GOS is unusually robust for an oligosaccharide, holding at pH 2.0 and surviving heating to 180 C, which takes it through acidified beverages, retort and baking. In the EU, Commission Delegated Regulation (EU) 2016/127 permits FOS and GOS in infant and follow-on formula up to 0.8 g/100 mL in a combination of 90% oligogalactosyl-lactose and 10% high molecular weight oligofructosyl-saccharose. In the US, FDA's 2018 guidance lists galactooligosaccharide among the isolated non-digestible carbohydrates that may be declared as dietary fibre, and the ingredient carries several GRAS notices, including GRN 620, 671, 721 and 1076. The point buyers most often get wrong is allergen status. GOS is made from lactose, and lactose comes from bovine milk, usually as whey permeate, so the finished powder is a milk-derived ingredient and must be declared as milk under EU Annex II, US FALCPA and India's packaged food labelling rules whatever the assay reads. Residual lactose is not trivial either, at up to 32% of dry matter in the 70% grade and up to 10% in the 90% grade, so no grade supports a lactose-free claim without the buyer's own assessment. That makes GOS suitable for lacto-vegetarians but not vegan, and kosher dairy rather than pareve. Nothing else of animal origin enters the process: no gelatin, no egg, no fish or crustacean material, and no soy, gluten or nut input. Every lot ships with a CoA covering GOS by HPLC, sugar profile, moisture, ash, heavy metals and microbiology, together with a signed allergen and origin declaration; AOAC Final Action 2021.01 is the collaboratively studied method where the destination is infant formula.