The Antioxidant Activity and Oxidative Stability of Cold‐Pressed Oils

Abstract

In our study, we characterized the antioxidant activity and oxidative stability of cold-pressed macadamia, avocado, sesame, safflower, pumpkin, rose hip, Linola, flaxseed, walnut, hempseed, poppy, and milk thistle oils. The radical scavenging activity of the non-fractionated fresh oil, as well as the lipophilic and hydrophilic fractions of the oil was determined using a 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The fatty acid composition of the fresh and stored oils was analyzed by gas chromatography. The acid value, peroxide value, p-anisidine value and conjugated diene and triene contents in the fresh oils, as well as in those stored throughout the whole period of their shelf life, were measured by CEN ISO methods. The antioxidant activity of the oils expressed as Trolox equivalent antioxidant capacity (TEAC), ranged from 0.17 to 2.32 mM. The lipophilic fractions of the oils were characterized by much higher antioxidant activity than the hydrophilic ones. There were no significant changes in fatty acid composition and only slight changes in the oxidative stability parameters of the oils during their shelf life. Through the assessment of the relationship between antiradical activity and the oxidative stability of oils, it is proposed that a DPPH assay predicts the formation of oxidation products in cold-pressed oils—however, the correlations differ in fractionated and nonfractionated oils.

Impact of Selected Chemical Characteristics of Cold-Pressed Oils on their Oxidative Stability Determined Using the Rancimat and Pressure Differential Scanning Calorimetry Method

“…Moderately high quenching of DPPH* was observed for milk thistle oils (2.14 and 2.56 at 3.18 TEAC). The similar antioxidant activity of milk thistle oil was reported by Prescha et al (2014). Examined sunflower oils differed significantly in their ability to scavenge free .…”

Volatile Oxidation Compounds and Stability of Safflower, Sesame and Canola Cold-Pressed Oils as Affected by Thermal and Microwave Treatments

“…The CD and CT values of sesame and safflower oils were lower than that of sesame oil from Macedonia 24 and also that of sesame and safflower oils 25 .…”

Perspectives on the use of seed oils in the South African diet

“…[20][21][22] Some issues, such as trans-fat content, lipid oxidation and genetic modification, apply to all edible oils. However, the toxicity of erucic acid, a fatty acid found in concentrations too high for human consumption in oil from older cultivars of rapeseed, applies only to rapeseed and canola oil.…”

“…20 Furthermore, as lipid oxidation takes place primarily at the oil and air interface, oils should be stored closed in a cool, dark place as they may oxidise faster once opened. However, it should also be born in mind that seed and vegetable oils inherently contain antioxidants, most importantly tocopherols 32,33 and phenolic compounds, 22,34 which inhibit lipid oxidation and keep the oils stable during storage and heating. Currently, food scientists are also investigating the addition of natural antioxidants, such as rosemary extract, as well as using the biofilms of these antioxidants to create active packaging to prevent the lipid oxidation of oils and oil-containing foods.…”

“…39 Thus, cold-pressed oils retain their health benefits and have a long shelf life stability owing to the presence of more natural antioxidants. They also generally have a lower smoking point, 22 and are therefore more suitable for moderate or cold temperature uses. Olive oil is an exception, and performs well at high temperatures because of its high content of phenolic compounds.…”