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Kinetics studies of chemical reactions and quality changes in conjugated linoleic acid (CLA) enriched milk treated with high-pressure sterilization Open Access


Other title
High-pressure sterilization
Conjugated linoleic acid
Type of item
Degree grantor
University of Alberta
Author or creator
Martinez, Sergio I.
Supervisor and department
Saldaña, Marleny (Agricultural, Food, and Nutritional Science)
Examining committee member and department
Guigard, Selma (Civil and Environmental Engineering)
Temelli, Feral (Agricultural, Food, and Nutritional Science)
Balasubramaniam, V (The Ohio State University)
Gänzle, Michael (Agricultural, Food, and Nutritional Science)
Department of Agricultural, Food, and Nutritional Science
Bioresource and Food Engineering
Date accepted
Graduation date
Doctor of Philosophy
Degree level
Conjugated linoleic acid (CLA), a bioactive lipid naturally found in milk, is thermally degraded through oxidation during thermal processing. Finding alternatives to enhance the retention of CLA is challenging. In this thesis, high-pressure sterilization (HPS) was used to enhance CLA retention in milk. In addition, the effect of HPS on some quality indicators was evaluated, including lactulose formation, inactivation of alkaline phosphatase, and retention of CLA during storage. When HPS was applied (600 MPa and 120˚C), 78% of the CLA was retained after 15 min, while only 20% was retained after 15 min at 0.1 MPa and 120˚C. The retention kinetics was represented with Weibull model. To further improve the retention of CLA in milk, seven antioxidants, mainly phenolic acids, were evaluated. Gallic acid and catechin resulted in the highest retention of CLA after treatments at 600 MPa and 120˚C. Temperature and pressure accelerated the formation of lactulose, with a maximum value of 650 mg L-1 at 120˚C, 600 MPa and 15 min. The HPS conditions needed to reduce 7-log of Bacillus amyloliquefaciens endospores in inoculated milk were determined as well as the effect of adding nisin (4-64 mg L-1 milk). The inactivation kinetics of alkaline phosphatase was determined. Results showed that the addition of nisin (≥16 mg L-1) significantly enhanced the inactivation of Bacillus amyloliquefaciens (7-log reduction) after 5 min of treatment at 600 MPa and 120˚C, while without nisin 10 min were required to achieve the same log reduction. For storage, milk treated at 600 MPa and 120˚C for 5 min was selected to evaluate the impact of HPS on the CLA retention and formation of hydroperoxides. During storage, milk with nisin added and treated with HPS delivered higher CLA retention and lower hydroperoxides concentration compared with the UHT equivalent process. The kinetic information obtained was used to build pressure-temperature diagrams for CLA retention and lactulose formation. These data can be further used to design HPS processes, achieving high CLA retention.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Martínez-Monteagudo, Sergio I., Marleny DA Saldaña, and John J. Kennelly. "Kinetics of non-isothermal oxidation of anhydrous milk fat rich in conjugated linoleic acid using differential scanning calorimetry." Journal of thermal analysis and calorimetry 107.3 (2012): 973-981Martínez-Monteagudo, Sergio I., et al. "Effect of pressure-assisted thermal sterilization on conjugated linoleic acid (CLA) content in CLA-enriched milk." Innovative Food Science & Emerging Technologies (2012).M.D.A. Saldaña and S.I. Martínez-Monteagudo (2013). Oxidative Stability of Fats and Oils Measured by Differential Scanning Calorimetry for Food and Industrial Applications, Applications of Calorimetry in a Wide Context - Differential Scanning Calorimetry, Isothermal Titration Calorimetry and Microcalorimetry, Dr. Amal Ali Elkordy (Ed.), ISBN: 978-953-51-0947-1, InTech, DOI: 10.5772/54486.

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