A novel bi‐enzymatic system for lactose conversion

Abstract

Summary The 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.