Galacto-oligosaccharides formation during manufacture of different varieties of yogurt. Stability through storage

Galacto-oligosaccharides (GOS) have interest in the food industry due to their recognized functional properties. In this work, we studied the effect of a commercial beta-galactosidase enzyme from Kluyveromyces lactis (YNL-2, GODO) and Lactobacillus acidophilus La-5, on GOS formation during the manufacture and storage of drinkable and stirred yogurts. In a preliminary step, GOS synthesis and lactose hydrolysis by beta-galactosidase was evaluated at different initial lactose concentrations and doses of enzyme. The GOS formation was favored with increasing of lactose concentration and enzyme doses, while the hydrolysis dominated at lower level of lactose. In turn, the presence of GUS was already evident at 45 min of fermentation in yogurts with addition of beta-galactosidase. Mean concentrations were 036 and 0.62 g/100 g for fresh drinkable and stirred yogurts, respectively. No changes in the GUS levels were observed through storage, indicating that they were stable in the products. The probiotic bacteria added were not able to produce GUS. The diminution of lactose was significant in yogurts with beta-galactosidase; contents of residual lactose were around 1.3 g/100 g. We obtained different varieties of reduced-lactose yogurts enriched in galacto-oligosaccharides. The presence of probiotic and prebiotic would increase the functional properties of yogurts. (C) 2015 Elsevier Ltd. All rights reserved.