Using iso-conversional kinetics to study the effect of α-tocopherol on the oxidation of formulated milk powder

Document Type

Abstract

Publication Date

2020

Publisher

American Dairy Science Association

Journal

Journal of Dairy Science

Volume

103

Issue

Suppl. 1

Pages

222

Language

en

Keywords

α-tocopherol, isoconversional methods, formulated milk powders

Abstract

Formulated milk powders are used in several applications, including recombined evaporated milk, yogurt, cheese, infant formulas, and beverages. During processing and subsequent storage, the fat in the powder can be oxidized and generate undesirable changes in the final product. The addition of antioxidants is a widespread practice to prevent the oxidation of formulated milk powders. In this work, we studied the effect of α-tocopherol on the kinetic parameters (pre-exponential factor, activation energy, and reaction model) during the oxidation of formulated milk powder. The oxidation kinetics were obtained using thermogravimetrical analysis (TGA) under non-isothermal conditions. Samples were formulated with either α-Tocopherol at 2% (α-Toc), hydrogen peroxide (H2 O2 ), and α-Toc+H2 O2 . Then, the formulated samples were oxidized at different heating rates (3, 6, 9, and 12°C min−1) in a temperature range of 100–300°C. In general, the addition of α-Toc delayed the oxidation of formulated milk powders. The lowest value of oxidation onset temperature was obtained for α-Toc, followed by α-Toc+H2 O2 and H2 O2 , yielding values of 128.2 ± 0.2, 231.8 ± 0.5, and 248.5 ± 0.2°C, respectively. The activation energy values were 58.12 ± 3.21, 46.91 ± 2.75, 69.43 ± 3.05, and 65.89 ± 5.12 kJ mol−1 for formulated milk powder, H2 O2 , α-Toc, and α-Toc+H2 O2 , respectively. The reaction model for the different samples was initially screened by fitting 13 different models. The most suitable reaction model to describe the oxidation of formulated milk powders was the Avrami-Erofeev model (A3). The obtained kinetic parameters were interpreted in terms of the oxidation mechanism. The obtained results may enable further process development, design, and optimization.

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