STABILITY OF BETA-GALACTOSIDASE FROM ASPERGILLUS-ORYZAE AND KLUYVEROMYCES-LACTIS IN DRY MILK POWDERS

A milk-based beverage powder with 2% vegetable fat and reduced levers of lactose is needed by some segments of the consumer market as well a s military units. To provide such, two commercial beta-galactosidases were dry-blended into milk powders made with coconut, cottonseed, cano la or sunflower oils and stored at -20, 4, 25, and 45 degrees C. Enzym e activity was measured monthly by reconstituting the powders and meas uring freezing point depression after incubation at 32 degrees C (opti mum for beta-galactosidase from Kluyveromyces lactis) and incubation a t 50 degrees C with pH adjusted to 5.0 (for activity of Aspergillus or yzae enzyme). Both enzymes retained >95% of original activity at -20 a nd 4 degrees C. Activity of K. lactis enzyme declined moderately at ro om temperature (approximate to 23 degrees C) and rapidly at 45 degrees C. The A. oryzae enzyme retained 93.4% of original activity after 6 m o at 45 degrees C.