Development of a Method Suitable for High-Throughput Screening to Measure Antioxidant Activity in a Linoleic Acid Emulsion

Abstract

An improved system for measuring antioxidant activity via thiobarbituric acid reactive substances and ferric thiocyanate assays is reported, on the basis of oxidation of a linoleic acid (LA) emulsion. Oxidation times were reduced from 20 h to 5 h by increasing the reaction temperature from 37 °C to 50 °C and with an acceptable precision of <10% coefficient of variation (CV). Antioxidants varying in polarity and chemical class—250 µM Trolox, quercetin, ascorbic acid and gallic acid—were used for method optimisation. Further reductions in reaction time were investigated through the addition of catalysts, oxygen initiators or increasing temperature to 60 °C; however, antioxidant activity varied from that established at 37 °C and 20 h reaction time—the method validation conditions. Further validation of the method was achieved with catechin, epicatechin, caffeic acid and α-tocopherol, with results at 50 °C and 5 h comparable to those at 37 °C and 20 h. The improved assay has the potential to rapidly screen antioxidants of various polarities, thus making it useful in studies where large numbers of plant extracts require testing. Furthermore, as this assay involves protection of a lipid, the assay is likely to provide complementary information to well-established tests, such as the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay.

Antioxidant Activity of Milk and Dairy Products

“…Food antioxidants are compounds that "scavenge" free radicals through various mechanisms. They directly neutralize free radicals generated during the oxidation process, reduce peroxide concentrations, repair oxidized membranes, bind iron to reduce the production of reactive oxygen species, or neutralize ROS via the metabolism of short-chain fatty acids and free cholesterol esters [9,10]. High consumption of nutritional antioxidants protects against the risk of lifestyle diseases (e.g., cardiovascular diseases, cancer, diabetes, and obesity) [3].…”

The Influence of Flaxseed Oil Cake Extract on Oxidative Stability of Microencapsulated Flaxseed Oil in Spray-Dried Powders

“…Light radiation and atmospheric oxygen are factors that initiate lipid oxidation and generate free radicals supporting the process [ 9 ]. As a result of oxidation, primary harmful oxidation products are formed, such as peroxides, which then break down into toxic secondary oxidation products, such as carbonyl compounds, conjugated dienes, and furans [ 11 ]. Secondary oxidation products contribute to a loss in nutritional and organoleptic properties of food [ 9 ].…”

Multi-Dimensional Antioxidant Screening of Selected Australian Native Plants and Putative Annotation of Active Compounds

“…These tests are mostly conducted in aqueous solution and may not adequately reveal antioxidants that are effective in lipid systems. On the other hand, a method for rapid screening of antioxidant activity in a lipid system has been recently developed [ 6 ], which has the potential to evaluate antioxidants that may be effective for use in oils, fats and emulsions. Moreover, Frankel and Meyer [ 7 ] and McDonald et al [ 8 ] recommended the use of orthogonal assays, i.e., those that test different activities (radical scavenging, chain-breaking, etc.)…”