Stability of β‐Galactosidase from Aspergillus oryzae and Khyveromyces lactis in Dry Milk Powders

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Abstract
A milk‐based beverage powder with 2% vegetable fat and reduced levels of lactose is needed by some segments of the consumer market as well as military units. To provide such, two commercial β‐galactosidases were dry‐blended into milk powders made with coconut, cottonseed, canola or sunflower oils and stored at −20, 4, 25, and 45°C. Enzyme activity was measured monthly by reconstituting the powders and measuring freezing point depression after incubation at 32°C (optimum for P‐galactosidase from Kluyveromyces luctis) and incubation at 50°C with pH adjusted to 5.0 (for activity of Aspergillus oryzae enzyme). Both enzymes retained >95% of original activity at −20 and 4°C. Activity of K. Zuctis enzyme declined moderately at room temperature (∼23°C) and rapidly at 45°C. The A. oryrae enzyme retained 93.4% of original activity after 6 mo at 45°C.