Two Types of Radicals in Whole Milk Powder. Effect of Lactose Crystallization, Lipid Oxidation, and Browning Reactions

• Published in: Journal of agricultural and food chemistry 2005-03, Vol.53 (5), p.1805-1811
• Main Authors: Thomsen, Marianne K, Lauridsen, Lene, Skibsted, Leif H, Risbo, Jens
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Crystallization; Electron Spin Resonance Spectroscopy; Food industries; Food Preservation; Free Radicals - analysis; Fundamental and applied biological sciences. Psychology; Lactose - chemistry; Lipid Peroxidation; Maillard Reaction; Milk - chemistry; Milk and cheese industries. Ice creams; Oxidation-Reduction
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf0485483

Whole milk powder was stored in closed vials at 60 °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. Keywords: Whole milk powder; radicals; ESR spectroscopy; lactose crystallization; Maillard reaction; nonenzymatic browning; lipid oxidation