Two types of radicals in whole milk powder. Effect of lactose crystallization, lipid oxidation, and browning reactions.
Whole milk powder was stored in closed vials at 60 degrees C to induce crystallization of lactose within a short time scale. After an induction period of 3-4 days simultaneous crystallization of lactose, increase of water activity, formation of browning products, and increase of radical content took place. Radicals detected before lactose crystallization were characterized by a narrow ESR spectrum (g = 2.006) and could be depleted by removal of oxygen and therefore were assigned to oxidation processes. Late-stage radicals present after crystallization of lactose gave much wider spectra (g = 2.0048) and were independent of oxygen availability and assigned to late-stage Maillard reaction products. The study indicates that the processes of lactose crystallization, browning, and formation of radical species (g = 2.0048) are strongly coupled, while lipid oxidation is less dependent on the other processes.
Thomsen
Marianne K
MK
Department of Food Science, Food Chemistry, Royal Veterinary and Agricultural University, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark.
Lauridsen
Lene
L
Skibsted
Leif H
LH
Risbo
Jens
J
D000818:Animals; D003460:Crystallization; D004578:Electron Spin Resonance Spectroscopy; D005519:Food Preservation; D005609:Free Radicals / Q000032:analysis*; D007785:Lactose / Q000737:chemistry*; D015227:Lipid Peroxidation; D015416:Maillard Reaction; D008892:Milk / Q000737:chemistry*; D010084:Oxidation-Reduction
D005609:Free Radicals; D007785:Lactose