Effect of lactose hydrolysis during manufacture and storage of drinkable yogurt

Abstract

Reduced-lactose yogurts are still not available in the Argentinean market despite the fact in Latin America the incidence of deficient lactose individual is very high. In this work, variables to hydrolyze the lactose (three levels of beta-galactosidase enzyme and the time of its addition) were evaluated during manufacture of natural and sweetened drinkable yogurts. Experimental yogurts (with enzyme) were compared with controls (without enzyme). The evolution of lactose content, pH, titratable acidity and syneresis were analyzed during 28 days of storage at 5ºC. Results showed feasibility in the simultaneous addition of enzyme and starter. The hydrolysis percentages in experimental yogurts ranged from 74 to 93% at the end of manufacture and stayed without changes during storage. For control yogurts, the lactose content decreased approximately 15%, which was doubled at 14 days. The inclusion of sucrose did not substantially affect the hydrolysis process. After 14 days, the pH and acidity in experimental yogurts were slightly higher and lower, respectively, in comparison to controls. On the other hand, the sensory panel found that the reduced-lactose and traditional yogurt where similar.