Chemical Compositional Changes in Over-Oxidized Fish Oils

Abstract

A recent study has reported that the administration during gestation of a highly rancid hoki liver oil, obtained by oxidation through sustained exposure to oxygen gas and incident light for 30 days, causes newborn mortality in rats. This effect was attributed to lipid hydroperoxides formed in the omega-3 long-chain polyunsaturated fatty acid-rich oil, while other chemical changes in the damaged oil were overlooked. In the present study, the oxidation condition employed to damage the hoki liver oil was replicated, and the extreme rancidity was confirmed. A detailed analysis of temporal chemical changes resulting from the sustained oxidative challenge involved measures of eicosapentaenoic acid/docosahexaenoic acid (EPA/DHA) omega-3 oil oxidative quality (peroxide value, para-anisidine value, total oxidation number, acid value, oligomers, antioxidant content, and induction time) as well as changes in fatty acid content, volatiles, isoprostanoids, and oxysterols. The chemical description was extended to refined anchovy oil, which is a more representative ingredient oil used in omega-3 finished products. The present study also analyzed the effects of a different oxidation method involving thermal exposure in the dark in contact with air, which is an oxidation condition that is more relevant to retail products. The two oils had different susceptibility to the oxidation conditions, resulting in distinct chemical oxidation signatures that were determined primarily by antioxidant protection as well as specific methodological aspects of the applied oxidative conditions. Unique isoprostanoids and oxysterols were formed in the over-oxidized fish oils, which are discussed in light of their potential biological activities.

Changes of Volatile Flavor Compounds in Large Yellow Croaker (Larimichthys crocea) during Storage, as Evaluated by Headspace Gas Chromatography–Ion Mobility Spectrometry and Principal Component Analysis

“…More specifically, after 120 d, the AV, POV, p-AV, and CDV were 7.62 ± 0.14 mg/g, 23.67 ± 0.55 meq/kg, 2.33 ± 0.03, and 33.57 ± 0.89, respectively. This observed increase in the AV is also consistent with previous studies [ 24 , 25 ] and is closely related to the free fatty acid content [ 26 , 27 ]. Previously, it was reported that the oxidation of fish meat during storage causes the breakage of ester bonds, which releases a large amount of free fatty acids and increases the AV [ 28 ].…”

Green Tea Extract Enhances the Oxidative Stability of DHA-Rich Oil

“…In another study, the incorporation of tea catechin (1 mM) or α-tocopherol (1 mM) in an oleic and linolenic acid–rich diacylglycerol oil, had no effect on the fatty acid composition of oil during a 10-day storage at 60 °C [ 52 ]. Similar to the results observed in this study for control and α-tocopherol-supplemented samples, Phung et al [ 53 ] reported an 8% decrease in EPA and DHA contents of hoki liver oil after 30 days of continuously bubbling the oil with oxygen gas and a 7% decrease when the oil was stored in an oven at 50 °C for 30 days.…”

Isoprostanoids, Isofuranoids and Isoketals – From Synthesis to Lipidomics

“…As OS is involved in many fields, e. g. environment, nutrition, disease, a wide variety of matrices are studied and analytical methods needs to be adapted. Thus, classical biological fluids (urine, [109][110][111] blood [99,112] ) or more specific ones (cerebrospinal fluid, [113,114] seminal fluid, secretome), animal tissues (muscle, kidney tissue, [115] brain tissue, [116] adipose tissue, [117] fibroblast cell line, spermatozoa, tumor biopsy) or plants or parts of plants (seaweed, oily extracts, oils, [118,119] seeds, [79] leaves, [120] etc.) will not follow the same sample preparation procedures (Figure 3).…”