A novel bi‐enzymatic system for lactose conversion

Abstract

SummaryThe potential of β‐galactosidase (β‐GAL) and glucose isomerase (GLI) to enhance the sweetening power of lactose and to generate galactooligosaccharides (GOS) and lactulose was studied. UF‐permeates of skim milk, sweet whey, acid whey and lactose solutions were incubated with β‐GAL and GLI. Lactose hydrolysis (LH) was 96–99%, glucose isomerisation (GI) about 53%. On a scale from 0 to 5, the intensity of sweetness increased from 1 to 3. The bi‐enzymatic process was also applied to yoghurt manufacture. Because of the inhibiting effect of calcium on GLI, the incubation was performed in UF‐permeates of skim milk. LH in yoghurt was 94%, whereas GI was 36% on average. Whey syneresis in yoghurt decreased from 12% to 5%. The sweetness increased from 1.4 to 2.9 on average. Applying the bi‐enzymatic system to 40% lactose solutions led to synthesis of about 20% prebiotic GOS. Products, such as 6‐galactobiose, allolactose and 6‐galactosyllactose were identified. About 1% lactulose was generated. Lactulose‐derived oligosaccharides were not found.