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Lu F.S.H.,Technical University of Denmark | Bruheim I.,Olympic Seafood AS | Haugsgjerd B.O.,NOFIMA | Jacobsen C.,Technical University of Denmark
Food Chemistry | Year: 2014

The main objective of this study was to investigate the effect of temperature towards lipid oxidation and non-enzymatic browning reactions in krill oil upon storage. Krill oil was incubated at two different temperatures (20 and 40°C) for 28 or 42 days. The oxidative stability of krill oil was assessed by peroxide value and anisidine value, measurement of lipid derived volatiles, lipid classes and antioxidants. The non-enzymatic browning reactions were assessed through the measurement of pyrroles, free amino acids content and Strecker-derived volatiles. The increase of incubation temperature firstly increased the lipid oxidation in krill oil and subsequently the non-enzymatic browning reactions. The occurrence of these reactions was most likely due to the reaction between α-dicarbonyl or carbonyl compounds with amino acids or ammonia. In addition to tocopherol and astaxanthin esters, the formation of pyrroles might help to protect the krill oil against lipid oxidation. © 2014 Elsevier Ltd. All rights reserved.


Lu F.S.H.,Technical University of Denmark | Bruheim I.,Olympic Seafood AS | Ale M.T.,Technical University of Denmark | Jacobsen C.,Technical University of Denmark
European Journal of Lipid Science and Technology | Year: 2015

The quality of krill products is influenced by their manufacturing process and could be evaluated by their degradation products from lipid oxidation and non-enzymatic browning reactions. The main objectives of this study were: (i) to investigate the effect of thermal treatment on these two reactions in krill products during their manufacturing process; and (ii) to understand and postulate the possible mechanisms for non-enzymatic browning reactions in krill products. Characterisation of krill products at different stages was obtained by determination of their lipid composition (lipid classes and phospholipids), antioxidant (α-tocopherol and astaxanthin esters) and volatile profiles (degradation products from lipid oxidation and Strecker degradation). The use of thermal treatment resulted in lipid oxidation and subsequently led to the development of non-enzymatic browning reactions in krill products during their manufacturing process. It is hypothesized that non-enzymatic browning reactions in krill products might occur through Maillard reaction or lipid peroxidation pathways. Practical applications: The quality of krill products is influenced by the temperature used during their manufacturing process, and the occurrence of their degradative reactions is influenced by the chemical composition and matrix of krill products. This work provides information about the possible mechanisms of the two most commonly found reactions in the food system namely, lipid oxidation and non-enzymatic browning reactions. This information is not only applicable to krill products but also to other food matrices containing lipid, protein, sugar, etc. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Lu F.S.H.,Technical University of Denmark | Bruheim I.,Olympic Seafood AS | Jacobsen C.,Technical University of Denmark
European Journal of Lipid Science and Technology | Year: 2015

The main objective of this study was to further investigate whether the occurrence of Strecker degradation in krill-based products is due to the presence of N-Acetylglucosamine (amino sugar derived from krill exoskeleton) or lipid-derived carbonyls. A simple model system comprising amino acids was incubated at 60°C for 0, 3, 9, and 24h with five selected lipid-derived carbonyls or five Strecker-derived volatiles or an amino sugar. The presence of both amino sugar and lipid-derived carbonyls (especially α,β-unsaturated aldehydes) caused non-enzymatic browning reactions: (i) pyrrole formation; (ii) browning development; and (iii) Strecker degradation of amino acids, with a faster reaction rate by amino sugar. In addition, the presence of a high level of Strecker degradation products might enhance pyrrole formation. Practical applications: This work provides information about the Strecker degradation of amino acids induced by amino sugar (N-Acetylglucosamine) and lipid-derived carbonyl compounds, and the increase of pyrrole formation is ascribed to the presence of a high level of Strecker degradation products. The obtained knowledge from this fundamental study explains the occurrence of Strecker degradation in krill products especially after enzymatic treatment due to the increased level of amino acids, lipid oxidation products and amino sugar derived from krill shell. This information is not only applicable to krill matrix but also to similar matrices from other food systems. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Thomsen B.R.,Technical University of Denmark | Haugsgjerd B.O.,Bergen and As | Griinari M.,CLANET ltd | Lu H.F.S.,Technical University of Denmark | And 4 more authors.
European Journal of Lipid Science and Technology | Year: 2013

The aim of this research was to investigate the oxidation progress and pathways of krill and fish oil during 21 days of incubation at 40°C. The oxidative stability of the oils was investigated through: (i) classical methods such as peroxide value (PV), anisidine value (AV), thiobarbituric reactive substance (TBARS), conjugated dienes and trienes, and antioxidant content, and (ii) advanced methods such as determination of volatiles content by dynamic headspace (DHS)-GC/MS, lipid classes, and pyrrole content. In addition, the oxidative stability of the oils was evaluated under accelerated oxidation conditions using the Oxipres™ at 90°C. The results from analysis of PV, AV, TBARS, conjugated dienes and trienes, and the antioxidant content suggested that krill oil was more oxidatively stable than fish oil. However, the color or other constituents of the krill oil might affect the result of these classical methods. Nevertheless, the conclusion was supported by the results of the Oxipres™ measurements, which showed that the oxygen consumption was higher for fish oil. Furthermore, the level of most volatile lipid oxidation products was higher for fish oil. The development of Strecker degradation products and pyrroles formed as a result of non-enzymatic browning reactions could only be observed in krill oil. The presence of pyrroles might have contributed to the higher oxidative stability of krill oil. Krill oil also contained a higher level of tocopherol, astaxanthin and phospholipids than fish oil, which could have resulted in better protection against oxidation. The results demonstrated that the classical methods for measuring oxidative deterioration of lipids were not useful for krill oil. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Lu F.S.H.,Technical University of Denmark | Bruheim I.,Olympic Seafood AS | Jacobsen C.,Technical University of Denmark
European Journal of Lipid Science and Technology | Year: 2015

Classical techniques such as Peroxide Value and Anisidine Value are not useful to evaluate the quality of krill oil. These techniques may underestimate lipid oxidation and other degradative reactions in krill oil. Therefore, the main objective of this study was to evaluate the quality of eight different commercial krill oil capsules through parameters such as: investigation of chemical compositions (bioactive compounds such as phospholipids, n-3 polyunsaturated fatty acids, antioxidants), hydrophobic pyrroles, and volatile profiles (lipid and Strecker-derived volatiles, pyridines, pyrazines, and their alkyl derivatives, sulphur and amino compounds). The data of chemical composition of krill oil were correlated well with those from volatile measurement. Through investigating volatile profile, new insights into the lipid oxidation and non-enzymatic browning reactions in krill oil were obtained, and the quality among different commercial krill oil products was differentiated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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