For vegetable oils with extremely different structure, oxidized, saturated and hydrolyzed, various electrical parameters, dielectric constant, dielectric loss factor and electrical conductivity and theirs’ temperature dependence were determined. Thus the frame of values characteristic for electrical properties for vegetable oils was evaluated. Model vegetable oil mixtures with significantly different basic oil quality indices (free fatty acid, iodine and Totox values) were prepared by adding oleic acids, synthetic saturated triglycerides, or oxidized safflower oil (Carthamus tinctorius) to the oleic type of sunflower oil. Dielectric constants, dielectric loss factors, quality factors, and electrical conductivities of model lipids were determined at frequencies from 50 Hz to 2 MHz and temperatures from 293.15 to 323.15 K. Dependence of these dielectric parameters on basic oil quality indices was investigated. Adding oleic acids to sunflower oil resulted in a lower dielectric constant and conductivities and higher quality factor. Reduced iodine values resulted in increased dielectric constants and quality factors, and decreased conductivities. Higher Totox values resulted in higher dielectric constants and conductivities at high frequencies, and lower quality factors. Dielectric constants decreased linearly with temperature, while conductivities followed Arrhenius’ law.
COBISS.SI-ID: 4329080
The influence of deodorization parameters (temperature, steam flow, time) on the phenolic content and radical scavenging effectiveness (RSE) of methanolic extracts of camelina oil was investigated and analysed by response-surface methodology (RSM). The phenolic content can be considered to be a linear function of all three parameters. A positive linear relationship between the content of phenolic compounds in deodorized oils and RSE was observed. Deodorization at 210 °C with a steam flow of 2.67 mL/h for 90 min resulted in the best preservation of phenolics, amounting to 29.9 mg/kg. The lowest reduction from RSE of 12.4 μM Trolox equivalents (TE)/g oil for the crude oil was observed for oil treated at 195 °C and 18 mL/h for 60 min with RSE of 10.1 μM TE/g oil. The lack of correlation between RSE or total phenolic content with oxidative stability of the deodorized oils suggests that antioxidants in scavenging radicals react by different mechanisms, depending on radical type and reaction medium.
COBISS.SI-ID: 4278136
The systematic study (that in this way has not yet been carried on) in which the influence of phenolic compounds structure on kinetics in scavenging free radicals was evaluated. The efficiencies of eight phenolic acids (chlorogenic, protocatechuic, caffeic, pcoumaric, sinapic, umbellic, rosmarinic and ferulic) in scavenging the alkylperoxyl radical generated in the βcarotene– linoleic acid emulsion system, the 2diphenyl1picrylhydrazyl radical (DPPH•) and the superoxide anion radical (O2•‾) were evaluated. The efficiency of the phenolic acids was estimated at the initial stage (t = 10 s) and expressed as the rate of DPPH• radical scavenging (RS DPPH•), the rate of O2•‾ radical scavenging (RFF) and the rate of βcarotene bleaching (RB). The highest RS DPPH• value for caffeic acid, followed by sinapic acid, showed the highest response in scavenging DPPH• radicals. According to its RFF value rosmarinic acid in comparison to the other investigated phenolic acids exhibited the highest response in O2•‾ radical scavenging. Among the investigatedphenolic acids, ferulic acid exhibited the lowest RB value indicating the strongest response in alkylperoxyl radical scavenging in the βcarotene–linoleic acid emulsion system, while in the presence of chlorogenic acid βcarotene bleached most rapidly. The effectiveness of the phenolic acids in scavenging free radicals was also determined in a classical way at a fixed endpoint. The results indicate that the kinetic data are a better discriminator for comprehensive characterization of an antioxidant. Expression of the results in terms of the kinetic approach does not take into account only the activity of an antioxidant but also provide information on how quickly the antioxidant acts. Therefore the results of antioxidant activity based on kinetic data in this paper are suggested as additional parameters to describe antioxidant activity.
COBISS.SI-ID: 4107640
Solvent composition has a large influence on measured antioxidant potential (AOP) of model polyphenols and red wines with DPPH. We have shown that incorporation of aqueous buffer in the assay medium results in higher reactivity and more complete oxidation of catechin and caftaric acid, that are among major polyphenolic constituents of wines. Consequently AOPs of red wines determined in buffered methanol are 1.5 to 1.6fold of values determined in pure methanol that is usually the solvent of choice. Parameters of DPPH assay should be standardized as minor differences in experimental procedures can account for large variations in determined AOP with DPPH for same samples.
COBISS.SI-ID: 4186488
Polyphenols are responsible for the major organoleptic characteristics of plant-derived foods and beverages. Here, we investigated the binding of several polyphenols to bovine serum albumin (BSA) at pH 7.5 and 25°C: catechins [(-)-epigallocatechin-3-gallate, (-)-epigallocatechin, (-)-epicatechin-3-gallate], flavones (kaempferol, kaempferol-3-glucoside, quercetin, naringenin) and hydroxycinnamic acids (rosmarinic acid, caffeic acid, p-coumaric acid). Fluorescence emission spectrometry and molecular docking were applied to compare experimentally determined binding parameters with molecular modelling. Among these polyphenols, (-)-epicatechin-3-gallate showed the highest Stern-Volmer modified quenching constant, followed by (-)-epigallocatechin-3-gallate. Similarly, (-)-epicatechin-3-gallate had the highest effect on the Circular Dichroic spectrum of BSA, while the changes induced by other polyphenols were negligible. Molecular docking predicted high binding energies for (-)-epicatechin-3-gallate and (-)-epigallocatechin-3-gallate for the binding site on BSA near Trp213. Our data reveal that the polyphenol structures significantly affect the binding process: the binding affinity generally decreases with glycosylation and reduced numbers of hydroxyl groups on the second aromatic ring.
COBISS.SI-ID: 4113784