Effect of liquid smoking on lipid hydrolysis and oxidation reactions during in vitro gastrointestinal digestion of European sea bass

Abstract

The effect of smoking using liquid smoke flavourings on the hydrolysis and oxidation of European sea bass lipids during in vitro digestion was investigated. The techniques used were ¹H NMR and SPME-GC/MS. The former proved that liquid smoking does not influence the extent of lipolysis, but prevents those lipid oxidation reactions that occur during in vitro digestion of unsmoked samples, giving rise to cis,trans-conjugated dienes associated with hydroperoxy/hydroxy groups. SPME-GC/MS corroborated the results obtained by ¹H NMR in relation to the antioxidant effect of smoking under gastrointestinal conditions. Smoked sea bass digests showed lower abundances of volatile oxidation markers derived from omega-3 and omega-6 lipids than unsmoked ones. Moreover, the lowest values were found in the digests of sea bass samples smoked with the flavouring showing the highest phenolic content. For the first time, the bioaccessibility of smoke flavouring components was evidenced, some of them well-known for displaying antioxidant activity.

Keywords: (9S,10E,12Z)-9-hydroperoxy-10,12-octadecadienoate (PubChem CID: 49852425); (E,E)-2,4-heptadienal (PubChem CID: 5283321); 1-penten-3-ol (PubChem CID: 12020); 2,6-di-tert-butyl-4-methylphenol (PubChem CID: 31404); 2-ethylfuran (PubChem CID: 18554); 5-hydroxymethyl-2-furfural (PubChem CID: 237332); 9-hydroxy-10E,12Z-octadecadienoic acid (PubChem CID: 5282944); Antioxidant; Digestion; Fish liquid smoking; Lipid oxidation; Proton nuclear magnetic resonance; Solid Phase Microextraction-Gas Chromatography/Mass Spectrometry; guaiacol (PubChem CID: 460); phenol (PubChem CID: 996); syringol (PubChem CID: 7041).