The present invention provides a process of producing a lactose concentrate, said process comprising the step of subjecting a partially demineralised aqueous lactose isolate to electrodialysis to produce a biotin-reduced lactose isolate containing at least 90% lactose by weight of dry matter and less than 2 mg ash per gram of lactose, and containing:. 0.02-1.5 mg sodium per gram of lactose;. 0.02-2 mg potassium per gram of lactose;. 0.05-1.5 mg chloride per gram of lactose;. 0.01-0.25 µg biotin per gram of lactose. The present invention also relates to a demineralised lactose concentrate having a reduced biotin content that can be produced by the aforementioned process. The invention further relates to an oligosaccharide-enriched biotin-reduced fraction that is obtained when lactose is separated before or after the electrodialysis step.