Chapter 4 - Low-Lactose, Prebiotic-Enriched Milk

Abstract

To mimic the multiple benefits of human milk oligosaccharides (HMOs), infant dairy products are usually supplemented with prebiotic galacto-oligosaccharides (GOS) and/or fructo-oligosaccharides. Instead of adding GOS to infant formula, an attractive alternative could be to form such oligosaccharides in situ during the typical treatment of milk with β-galactosidases to eliminate lactose. The objective of this work was to obtain milk with a significant presence of GOS and, at the same time, a low content of lactose. The formation of GOS in skim milk was studied with the β-galactosidases from Bacillus circulans and Kluyveromyces lactis, at 4 and 40°C. With B. circulans β-galactosidase, the maximum GOS concentration was obtained when 50% of the initial lactose had disappeared. In contrast, the maximum GOS yield with K. lactis enzyme was achieved at 95% of lactose depletion. Using an enzyme dosage of 0.1% (v/v), GOS concentration with K. lactis β-galactosidase reached 7.0g/L—the HMOs concentration in breast milk is between 5 and 15g/L—with only 2.1g/L of residual lactose (initially 45g/L). The major GOS synthesized by this enzyme were 6-galactobiose, allolactose, and 6′-O-β- galactosyl-lactose. Thermal inactivation after enzymatic treatment with β-galactosidase from K. lactis could provide low-lactose milk with the extra benefit of a significant content of prebiotic GOS