Document Type

Thesis - Open Access

Award Date

2019

Degree Name

Master of Science (MS)

Department / School

Dairy Science

First Advisor

ergio Martinez Monteagudo

Keywords

Antioxidants, DSC, isoconversional methods, Milk fat, Milk formulate, Oxidation

Abstract

Milk fat is a versatile ingredient because of its nutritional value, functionality, and flavor. During processing and storage, milk fat may undergo oxidation resulting in many undesirable changes such as unpleasant flavor and aroma, and formation of toxic compounds. A common practice to prevent the oxidation of milk fat is by the addition of antioxidants. It is worth to mention that little is known on the effect of antioxidants on the oxidation kinetics. In this work, the effect of selected antioxidants on the oxidation kinetics of anhydrous milk fat (AMF) under non-isothermal conditions was investigated. AMF with an addition of either butylated hydroxytoluene (BHT), α-Tocopherol (α-Toc), or β-carotene (β-Car) at four different concentrations (0.02, 0.07, 0.2, and 0.4%) were oxidized using differential scanning calorimetry (DSC) at different constant heating rates (3, 6, 9, and 12°C min-1) in a temperature range of 100-400°C. DSC spectra were analyzed according to the Kissinger-Akahira-Sunose (KAS) method, from which the kinetic triplet was obtained (pre-exponential factor (A), apparent activation energy (Ea), and reaction model (𝑓(∝)). In general, the concentration of antioxidant increased the onset temperature of oxidation (Ton) when comparing to the Ton of AMF without antioxidant. The Ea values were 82.73 ± 5.51, 93.14 ± 6.24, 68.06 ± 3.52, and 58.51 ± 7.51 kJ mol-1 for AMF, BHT, β-Car, and α-Toc, respectively. Remarkably, the addition of 0.2% of α-Toc inhibited the oxidation reaction by 9-fold, judging the constant rate. The obtained kinetic parameters were interpreted in term of oxidation mechanism. The oxidation of milk fat was best described by the Avrami-Erofeev model. The obtained kinetic triplet (Ao, Eo, and 𝑓(∝)) was used to systematically evaluate the role antioxidants. The addition of antioxidants significantly delayed the oxidation, being more effective α-Toc followed by β-Car and BHT. The outcomes of this study may enable off-line simulation and development of a databank.

Library of Congress Subject Headings

Milkfat -- Analysis.
Oxidation.
Antioxidants.
Chemical kinetics.

Format

application/pdf

Number of Pages

108

Publisher

South Dakota State University

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Rights Statement

In Copyright