Control of lactose crystallization in "dulce de leche" by Beta-D-Galactosidase activity from permeabilized Kluyveromyces lactis cells.

Abstract

Feasibility of controlling lactose crystallization in "dulce de leche" by permeabilized Kluyveromyces lactis cells was studied. Optimum temperature for lactase activity was 45°C. Stability of the enzyme system remained practically unaltered during storage at room temperature or below for up to 7 mo. Degree of lactose hydrolysis in milk was determined as a function of the content of permeabilized cells. Addition of 400 or 800 rag/liter of permeabilized cells to milk used to make "dulce", followed by 2.5 or 3.5 h incubation at 35°C, resulted in hydrolysis of 45.02 and 69.13% of the lactose. There was no lactose crystallization after 120 days storage in products treated by permeabilized cells. The sensory qualities of the "dulces" were similar to those of the control.