Galactooligosaccharide-enriched lactose-free milk production, health benefits, and food applications

Lactase non-persistence occurs in approximately 65–70% of adults worldwide, contributing to the demand for lactose-free dairy products. Conventional lactose hydrolysis with β-galactosidase increases glucose and galactose concentrations, which can raise milk sweetness and alter sensory quality. Hybrid membrane–enzymatic processes help preserve product characteristics while generating lactose-rich streams that can serve as substrates for galactooligosaccharide (GOS) production through transgalactosylation. However, monosaccharide accumulation limits GOS yield and necessitates downstream purification. Emerging microbial strategies may complement membrane separation, including monosaccharide removal by lactose-negative yeasts, combined or sequential microbial processes, and lactose-positive Kluyveromyces species that utilize lactose and monosaccharides. This graphical review summarizes GOS formation during lactose-free milk processing, associated health benefits and food applications, and recent microbial purification approaches. These biotechnological approaches may complement existing purification processes, although their industrial and economic feasibility requires further validation.