Xylo-oligosaccharides (XOS)

Xylo-oligosaccharides are chains of two to seven xylose units joined by beta-(1,4) bonds, with xylobiose, xylotriose and xylotetraose making up the bulk and small amounts of xylopentaose through xyloheptaose behind them. The raw material is the corncob of Zea mays subsp. mays, the woody core left once the kernels are stripped, which is where the plant concentrates its xylan. The cob is milled, the xylan is released and cut with an endo-1,4-beta-xylanase (EC 3.2.1.8) produced by Trichoderma reesei, and the hydrolysate is decolourised, demineralised and chromatographically enriched before spray drying. Purity is decided at that enrichment step, which is why one process yields XOS 95P at 95% and XOS 70P at 70% XOS on a dry basis alongside a 70% syrup. Xylobiose, the dominant oligomer, has the formula C10H18O9 and a molecular weight of 282.24; the mixture itself carries no single CAS number. XOS is one of the few prebiotic oligosaccharides with a statutory specification a buyer can point at. Commission Implementing Regulation (EU) 2018/1648 authorised it as a novel food on the strength of an EFSA opinion, and the Union list entry fixes XOS 95P at 95 g/100 g minimum with xylobiose at 25 to 45, xylotriose at 27 to 35 and xylotetraose at 10 to 20 g/100 g, moisture at 5% maximum, ash at 0.3% maximum, pH 3.5 to 5.0, free xylose at 1.0 g/100 g maximum and glucose at 2.0 g/100 g maximum, with lead below 0.5 mg/kg, arsenic below 0.3 mg/kg, copper below 5.0 mg/kg, and Salmonella and E. coli negative. The same annex sets use levels - 14 g/kg in breads, breakfast cereals and biscuits, 3.5 g/kg in yoghurt and soy drinks, 30 g/kg in fruit spreads and chocolate - and requires the label designation 'Xylo-oligosaccharides'. Functionally the material holds across pH 2.5 to 8 and up to 100 C, and the working inclusion is low, typically 1 to 4 g in a daily serving, which keeps both cost-in-use and total added carbohydrate well below what a fibre dosed at 5 to 10 g would impose. Origin is clean and that is part of the commercial appeal. The material is wholly plant-derived from a cereal by-product, so it is vegan and vegetarian, and no milk, egg, soy, fish, crustacean or nut material touches the process. Maize is not a gluten-bearing grain and the cob carries no kernel protein, so gluten-free status is supportable on test; non-GMO maize declarations and kosher and halal certification are available on request. Buyers should keep the grades apart when writing a specification. The 95% and 70% food grades are purified powders and syrups sold on assay; the 35% grades that circulate in the animal feed trade are usually XOS carried on milled corncob or a starch carrier, which is a different article with a different specification and a different tariff position. Every lot ships with a CoA giving XOS and the DP2 to DP4 profile by HPLC, moisture, ash, pH, heavy metals and microbiology.