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Food Structure

Authors

Zenichi Saito

Abstract

Two kinds of whey powder, one containing only amorphous lactose, and the other containing precrystallized lactose, and spray-dried amorphous lactose were examined for particle structure by scanning electron microscopy. Lactose crystallization under 75th relative humidity was studied by X-ray diffraction analysis. Scanning electron microscopy appeared to detect changes due to lactose crystallization on the smooth surface of the particles examined. Lactose crystallization s tarted within 30 minutes after exposure to the humid atmosphere. Both a-lactose hydrate and B-lactose crystals were detected in the s pray- dried amorphous lactose by X -ray diffraction within 40 minutes under the humid conditions. Only crystals of ex-lactose hydrate developed in the whey powders. Additional crystallization of lactose in the amorphous portion of precrystallized whey powder was seen by scanning electron microscopy but increased crystallinity was not clearly detected by X-ray diffraction analysis. Several physical treatments involving storage at - 20 to 550C along with a desiccating agent, failed to crystallize B-lactose in the whey powders. It is hypothesized that the presence of milk serum solids inhibited the crystallization of B-lactose.

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