Effect of reduction of lactose in yogurts by addition of β-galactosidase enzyme on volatile compound profile and quality parameters (original) (raw)

Biochemical and thermal properties of β-galactosidase enzymes produced by artisanal yoghurt cultures

Food Chemistry, 2010

b-Galactosidases, produced by pure and mixed cultures of Streptococcus thermophilus 95/2 (St 95/2) and Lactobacillus delbrueckii ssp bulgaricus 77 (Lb 77) isolated from the Toros mountain region of Turkey, were characterised with respect to their biochemical and thermal properties. Optimum pH and temperature for maximum activity were determined and these enzymes were stable in the pH range 7-9 and in the temperature range 20-37°C, retaining 80-90% of their initial activities. The inactivation energies of bgalactosidase from Lb 77, St 95/2 and mixed culture (Lb 77 and St 95/2) were 51.3, 44.0 and 48.3 kcal mol À1 , respectively. Moreover, thermodynamic (DG, DS, DH) and kinetic constants (K m and V max) were determined and effects of metal ions were investigated. As a result, these enzymes could be considered as potential candidates for lactose hydrolysis of milk and milk products.

Factors Affecting the Ability of a High β-Galactosidase Yogurt to Enhance Lactose Absorption

Journal of Dairy Science, 1994

Lactose in yogurt is better absorbed by lactase-deficient subjects than is an equivalent quantity of lactose in milk, presumably because of the microbial activity of the P-galactosidase present in yogurt. In this study, we describe a process that increases the P-galactosidase of yogurt 5-to 6-fold and the ability of this high lactase yogurt to enhance lactose absorption in lactase-deficient subjects. These subjects ingested the yogurt meals after a 12-h fast, and lactose malabsorption was determined by measuring breath hydrogen. Breath hydrogen was reduced 39% following ingestion of high lactase yogurt from that after consumption of conventional yogurt, indicating that the high lactase yogurt enhanced lactose absorption. However, the reduction after high lactase yogurt was less than expected, given the 5to 6-fold increment in P-galactosidase measured in vitro. In vivo activity of &galactosidase requires that the enzyme resist acid denaturation in the stomach. The P-galactosidase in high lactase yogurt was much less acid resistant than was the 0-galactosidase in conventional yogurt, and the relative inability of high lactase yogurt to enhance lactose absorption was likely due to the