The neutral HMOs are considered to be the most relevant factors for the development of the intestinal microbiota typical for breastfed infants, whereas the acidic oligosaccharides play an important role in the prevention of adhesion of pathogenic bacteria to the intestinal epithelial surface. While specific glycans may act as decoys to inhibit binding of specific pathogens, the advantage of HMOs is likely due to the constellation of diverse glycan structures which act in concert to confer protection to infants from many bacterial, viral, fungal and other pathogens. The present work, employing concentration techniques on dairy streams at pilot scale combined with advanced mass spectrometry, is the first to discover numerous high-molecular weight fucosecontaining oligosaccharides in a whey stream of bovine milk. Fucosylated oligosaccharides were confirmed using accurate tandem mass spectrometry. The structures described herein likely evaded prior characterization because of their low abundance relative to the major BMOs. An analogous Tubuloside-A observation on human milk was reported by Finke et al.. In that work, they reported that lactose and predominant oligosaccharides had to be removed by chromatography to allow the detection of minor high molecular weight oligosaccharides. In the present work, BMOs were fractionated and 
concentrated by membrane filtration and lactose was completely removed by solid-phase extraction prior to mass spectrometry. The discovery of such a large number of fucose-containing oligosaccharides in bovine milk is promising for translation of these bioactive molecules into functional foods. HMOs containing fucose are associated with lower risk of diarrhea and respiratory diseases in breast-fed infants. Thus milk oligosaccharides, having structures analogous to cell surface receptors, may act as competitive inhibitors of pathogen binding to their glycoconjugate receptors. In particular, HMOs containing a 1,2-linked fucose inhibit the stable toxin-producing Escherichia coli in vitro and its toxin-induced secretory diarrhea in vitro and in vivo, and Campylobacter jejuni in vitro and in vivo. Mother liquor, a low-value by-product of whey and lactose manufacture, is a rich source of BMOs. Fractionation and concentration of these oligosaccharides by membrane filtration led to the production of a powder enriched in oligosaccharides and low in lactose. Structural analysis of the oligosaccharides present in this product through high-resolution and sensitive mass spectrometry revealed the presence of previously unreported highmolecular weight BMOs including some fucosylated structures. Mother liquor is a be er source of milk oligosaccharides than either mature bovine milk or colostrum. Extraction and enrichment or isolation of oligosaccharides from whey UF permeate or mother liquor can result in the development of biofunctional oligosaccharides ingredients for the food, beverage, and infant formula industries, add value to the waste streams of dairy production, and also reduce waste disposal costs for the dairy industry. The presence of oligosaccharides containing GlcNAc, fucose and 9-methoxycamptothecine sialic acid make mother liquor potentially an ideal dairy source for commercial production of oligosaccharides.