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Lactose Crystallization in Skim Milk Powder Observed by Hydrodynamic Equilibria, Scanning Electron Microscopy and 2 H Nuclear Magnetic Resonance
Author(s) -
LAI HSIMEI,
SCHMIDT SHELLY J.
Publication year - 1990
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1990.tb01582.x
Subject(s) - crystallization , amorphous solid , lactose , scanning electron microscope , analytical chemistry (journal) , chemistry , crystallography , differential scanning calorimetry , sorption , deuterium , materials science , chromatography , thermodynamics , organic chemistry , composite material , physics , quantum mechanics , adsorption
Lactose crystallization in medium heat nonfat dry milk as a function of water activity (0.01 to 0.94 a w ) and time (2 wk) at constant temperature (20°C) was investigated by changes in moisture during the equilibration period and scanning electron microscopy. Discontinuous sorption behavior observed at a w 0.54 and above was ascribed to lactose undergoing a transition from the amorphous to the crystalline state. Scanning electron micrographs taken throughout the equilibration period revealed increasing lactose crystallization with time at and above a w 0.54. Deuterium( 2 H) Nuclear Magnetic Resonance (NMR) spectroscopy was used to monitor the water mobility during the amorphous to crystalline state transition. Changes in water mobility were found to be directly related to the observed moisture changes and the transition of lactose from the amorphous to crystalline state.