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Article

Hydroxytyrosol Prevents Oxidative Deterioration in Foodstuffs Rich in Fish Lipids

Manuel Pazos*, Ana Alonso, Isabel S

nchez and Isabel Medina

Instituto de Investigaciones Marinas (CSIC), Eduardo Cabello 6, E-36208 Vigo, Spain

J. Agric. Food Chem., 2008, 56 (9), pp 3334–3340

DOI: 10.1021/jf073403s

Publication Date (Web): April 22, 2008

* Author to whom correspondence should be addressed (e-mail mpazos@iim.csic.es; telephone +34 986 231930 ; fax +34 986 292762).

Abstract

Hydroxytyrosol, a natural phenolic compound obtained from olive oil byproduct, was characterized as an antioxidant in three different foodstuffs rich in fish lipids: (a) bulk cod liver oil (40% of ω-3 PUFAs), (b) cod liver oil-in-water emulsions (4% of ω-3 PUFAs), and (c) frozen minced horse mackerel (Trachurus trachurus) muscle. Hydroxytyrosol was evaluated at different concentration levels (10, 50, and 100 ppm), and its antioxidant capacity was compared against that of a synthetic phenolic, propyl gallate. Results proved the efficiency of hydroxytyrosol to inhibit the formation of lipid oxidation products in all tested food systems, although two different optimal antioxidant concentrations were observed. In bulk oil and oil-in-water emulsions, a higher oxidative stability was achieved by increasing the concentration of hydroxytyrosol, whereas an intermediate concentration (50 ppm) showed more efficiency, delaying lipid oxidation in frozen minced fish muscle. The endogenous depletion of α-tocopherol and ω-3 polyunsaturated fatty acids (ω-3 PUFAs) was also inhibited by supplementing hydroxytyrosol in minced muscle; however, the consumption of the endogenous total glutathione was not efficiently reduced by either hydroxytyrosol or propyl gallate. A concentration of 50 ppm of hydroxytyrosol was best to maintain a longer initial level of α-tocopherol (approximately 300 µg/g of fat), whereas both 50 and 100 ppm of hydroxytyrosol were able to preserve completely ω-3 PUFAs. Hydroxytyrosol and propyl gallate showed comparable antioxidant activities in emulsions and frozen fish muscle, and propyl gallate exhibited better antioxidant efficiency in bulk fish oil.

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