文摘
The formation of galactooligosaccharides (GOS) in skim milk during treatment with several commercial ¦Â-galactosidases (Bacillus circulans, Kluyveromyces lactis and Aspergillus oryzae) was analysed in detail, at 4 and 40 ¡ãC. The maximum GOS concentration was obtained at a lactose conversion of approximately 40-50 % with B. circulans and A. oryzae ¦Â-galactosidases, and at 95 % lactose depletion for K. lactis ¦Â-galactosidase. Using an enzyme dosage of 0.1 % (v/v), the maximum GOS concentration with K. lactis ¦Â-galactosidase was achieved in 1 and 5 h at 40 and 4 ¡ãC, respectively. With this enzyme, it was possible to obtain a treated milk with 7.0 g/L GOS ? the human milk oligosaccharides (HMOs) concentration is between 5 and 15 g/L - and with a low content of residual lactose (2.1 g/L, compared with 44-46 g/L in the initial milk sample). The major GOS synthesised by this enzyme were 6-galactobiose [Gal-¦Â(1 ¡ú 6)-Gal], allolactose [Gal-¦Â(1 ¡ú 6)-Glc] and 6¡ä-O-¦Â-galactosyl-lactose [Gal-¦Â(1 ¡ú 6)-Gal-¦Â(1 ¡ú 4)-Glc].
