Approaches of lipid oxidation mechanisms in oil matrices using association colloids and analysis methods for the lipid oxidation

Revisiting polar paradox: antioxidant activity in bulk oil using selected phenol lipids

The purpose of this work was to re-evaluate the polar paradox theory (PPT) that explains the relationships between the efficacy of antioxidants, their polarity, and their environments. In this study, ascorbic acid (AA), ascorbyl palmitate (AP), gallic acid (GA), gallyl palmitate (GP), Trolox (TR), α-tocopherol (TO), resveratrol (R), and resveratryl palmitate (RP) were employed to assess conjugated dienoic acid (CDA), the p-anisidine value (p-AV), headspace oxygen content, and hexanal formation in a bulk oil system. TR, TO, R, and RP showed better antioxidant activities in CDA and p-AV and higher headspace oxygen content than AA, AP, GA, and GP. AA showed lower hexanal formation than AP, whereas GP, TO, and RP had better antioxidant activity than their derivatives. These findings suggest that the PPT might be useful to explain the oxidation that occurs at the air-oil interface/association colloids but applying it to other assays might not appropriate.

Evaluation biodegradable films with green tea extract for interleafing sliced meat products

A selection of formulations with different polymers and concentrations of green tea extract was conducted for application as interleafs in sliced meat products. Films were formulated using cellulose acetate, corn starch, and chitosan with the addition of 1.0, 2.5, and 5.0% green tea extract. Higher antioxidant activity was observed with the 1.0% concentration of green tea extract (P < 0.05), regardless of the formulation, with continuous release of the extract for up to 60 days and average IC50 of 0.09 and 0.31 mg/mL for the corn starch and chitosan active films, respectively. Interleafing the sliced ham resulted in lower lipid oxidation after 60 days of storage (P < 0.05). Starch-based films with green tea extract were effective, significantly reducing lipid oxidation in sliced and interleafed cooked ham, suggesting their potential to extend the shelf life of these refrigerated products.

Reduction of toxic aldehydes in heated flaxseed oil using sesame and perilla protein enzymatic hydrolysates

Reducing ability of sesame meal protein enzymatic hydrolysates (SMH) and perilla protein enzymatic hydrolysates (PMH) on the content of toxic aldehydes including acetaldehyde, formaldehyde, 2-hydroxylhexenal (HHE), and 2-hydroxyl nonenal (HNE), were evaluated in heated flaxseed oil at concentrations ranging from 0.01 to 1.0 g. Adding SMH and PMH decreased the formation of secondary oxidation products and toxic aldehydes during heating. In particular, HHE and HNE were not detected, even at 0.01 g of protein concentration. Free radical scavenging activities in heated flaxseed oil significantly increased when 1.0 g of SMH and PMH were added (p < 0.05). Some volatiles including 2-ethylpyridine, pyrazines, and trimethylamine were formed or increased substantially in flaxseed oils with higher concentrations of SMH and PMH. In general, SMH showed higher antioxidative activity and reducing ability on the toxic aldehydes than PMH. Plant protein enzymatic hydrolysate could control the formation of toxic aldehydes during oxidation of ω-3 edible oil.

Impact of dietary n-6/n-3 fatty acid ratio of atherosclerosis risk: A review

Atherosclerosis is a causative factor associated with cardiovascular disease (CVD). Over the past few decades, extensive research has been carried out on the relationship between the n-6/n-3 fatty acid ratio of ingested lipids and the progression of atherosclerosis. However, there are still many uncertainties regarding the precise nature of this relationship, which has led to challenges in providing sound dietary advice to the general public. There is therefore a pressing need to review our current understanding of the relationship between the dietary n-6/n-3 fatty acid ratio and atherosclerosis, and to summarize the underlying factors contributing to the current uncertainties. Initially, this article reviews the association between the n-6/n-3 fatty acid ratio and CVDs in different countries. A summary of the current understanding of the molecular mechanisms of n-6/n-3 fatty acid ratio on atherosclerosis is then given, including inflammatory responses, lipid metabolism, low-density lipoprotein cholesterol oxidation, and vascular function. Possible reasons behind the current controversies on the relationship between the n-6/n-3 fatty acid ratio and atherosclerosis are then provided, including the precise molecular structures of the fatty acids, diet-gene interactions, the role of fat-soluble phytochemicals, and the impact of other nutritional factors. An important objective of this article is to highlight areas where further research is needed to clarify the role of n-6/n-3 fatty acid ratio on atherosclerosis.

Evaluation of oxidative stability of rice oil from brown rice flour under thermal oxidation and light irradiation

Effects of autoxidation and light irradiation on the oxidative stability were evaluated in rice oil from two brown rice flours including 'Baromi2' and 'Samkwang'. 'Baromi2' is a newly developed variety for rice flour production while 'Samkwang' is a typical rice variety as a control. Degree of oxidation and volatile profiles were evaluated in rice oil stored at 60 °C or under fluorescent light at 25 °C. The oil yields of 'Baromi2' and 'Samkang' were 2.63 and 1.78%, respectively whereas rice oil from 'Baromi2' had lower degree of unsaturation than 'Samkang'. Rice oil from 'Samkwang' possessed higher volatile compounds and more oxidized products during autoxidation whereas rice oil from 'Baromi2' had more oxidation products under light irradiation. Hexanal and 2-heptenal were major headspace volatile from heated rice oil while 2-heptenal and 1-octene-3-ol were main volatiles from light irradiated rice oil, which implies the involvement of singlet oxygen in rice oil during photooxidation.

Recent advances in understanding the interfacial activity of antioxidants in association colloids in bulk oil

The chemical stability of edible oils rich in polyunsaturated fatty acids (PUFAs) is a major challenge within the food and supplement industries, as lipid oxidation reduces oil quality and safety. Despite appearing homogeneous to the human eye, bulk oils are actually multiphase heterogeneous systems at the nanoscale level. Association colloids, such as reverse micelles, are spontaneously formed within bulk oils due to the self-assembly of amphiphilic molecules that are present, like phospholipids, free fatty acids, and/or surfactants. In bulk oil, lipid oxidation often occurs at the oil-water interface of these association colloids because this is where different reactants accumulate, such as PUFAs, hydroperoxides, transition metals, and antioxidants. Consequently, the efficiency of antioxidants in bulk oils is governed by their chemical reactivity, but also by their ability to be located close to the site of oxidation. This review describes the impact of minor constituents in bulk oils on the nature of the association colloids formed. And then the formation of mixed reverse micelles (LOOH, (co)surfactants, or antioxidations) during the peroxidation of bulk oils, as well as changes in their composition and structure over time are also discussed. The critical importance of selecting appropriate antioxidants and surfactants for the changes of interface and colloid, as well as the inhibition of lipid oxidation is emphasized. The knowledge presented in this review article may facilitate the design of bulk oil products with improved resistance to oxidation, thereby reducing food waste and improving food quality and safety.