Antioxidant activity of ginger extract in sunflower oil

The antioxidant activity of dichloromethane extract from ginger was evaluated during 6 months of storage of refined sunflower oil at 25 and 45 °C. Free fatty acid (FFA) content, peroxide value (POV) and iodine value (IV) were used as criteria to assess ginger extract as an antioxidant. After 6 months of storage at 45 °C, sunflower oil containing 1600 and 2400 ppm ginger extract showed lower FFA contents (0.083 and 0.080%) and POVs (24.5 and 24.0 meq kg^?1) than the control sample (FFA contents 0.380%, POV 198.0 meq kg^?1). Sunflower oil containing 200 ppm butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) showed FFA contents of 0.089 and 0.072% and POVs of 26.5 and 24.7 meq kg^?1 respectively after 6 months of storage at 45 °C. Similarly, after 6 months of storage at 45 °C, IVs of sunflower oil containing 1600 and 2400 ppm ginger extract were 80 and 92 respectively, higher than that of the control sample (53). However, IVs of sunflower oil treated with 200 ppm BHA and BHT were 94 and 96 respectively after 6 months of storage at 45 °C. These results illustrate that ginger extract at various concentrations exhibited very strong antioxidant activity, almost equal to that of synthetic antioxidants (BHA and BHT). Ginger extract also showed good thermal stability and exhibited 85.2% inhibition of peroxidation of linoleic acid when heated at 185 °C for 120 min. Therefore the use of ginger extract in foods is recommended as a natural antioxidant to suppress lipid oxidation. © 2003 Society of Chemical Industry     

Stabilization of sunflower oil by garlic extract during accelerated storage

Efficacy of garlic extract in stabilizing sunflower oil during accelerated storage has been studied. Extracts of garlic were prepared in different solvents; extract yield was in the range of 6.24–23.2% and antioxidant activity range in the linoleic acid system was 14.1–93.2%. Being highest in yield and antioxidant potential, methanolic extract was thermally evaluated by heating the extract at 185 °C for different intervals, i.e. 0–80 min and evaluating antioxidant activity of the heated extract in the linoleic acid system (71.6% inhibition). Methanolic extract of garlic at three different concentrations, i.e. 250 (SFO-250), 500 (SFO-500) and 1000 ppm (SFO-1000) were added to preheated RBD sunflower oil. BHA (SFO-BHA) and BHT (SFO-BHT) at 200 ppm served as standards besides the control. Weight gain (WG), antioxidant activity index (AAI), free fatty acid (FFA) content, peroxide value (PV), conjugated dienes (CD), conjugated trienes (CT) and thiobarbituric acid-reactive substances (TBARS) were taken as parameters for evaluation of effectiveness of garlic in stabilization of sunflower oil. Results from different parameters were in agreement with each other, suggesting the highest efficiency of SFO-1000, followed by SFO-BHT, SFO-BHA, SFO-500, SFO-250 and Ctrl. Results reveal garlic to be a potent antioxidant for stabilization of sunflower oil.     

The increase in oxidative stability of sunflower oil enriched with Nigella sativa L. Seed extracts

Nigella sativa L. seeds are rich sources of phenolic compounds. The aim of this study was to evaluate the efficiency of Nigella seed extract as natural antioxidant compared with butylated hydroxytoluene (BHT) during accelerated oxidation of edible vegetable oils at 120 °C. The modifications during heating were monitored by 3D-front-face fluorescence spectroscopy. The fluorescence spectra were obtained with excitations from 280 to 500 nm and emission wavelengths from 300 to 550 nm and analysed using independent components analysis. Decomposition products formed during heating were also evaluated by means of ¹H-NMR spectroscopy and classic chemical methods such as anisidine value and viscosity. The results of the study clearly indicate that the natural seed extract at a level of 800 ppm exhibited antioxidant effects similar to those of the synthetic antioxidant BHT at a level of 200 ppm and thus contributes to an increase in the oxidative stability of the oil.     

Loss of tocopherols and formation of degradation compounds at frying temperatures in oils differing in degree of unsaturation and natural antioxidant content

Samples of oils of different degrees of unsaturation, namely palm olein, olive oil, high‐linoleic sunflower oil, high‐oleic sunflower oil, rapeseed oil and soybean oil, were heated at 180 °C for 2, 4, 6, 8 and 10 h in the presence or absence of their natural antioxidants. Also, tocopherol‐stripped oils were supplemented with α‐tocopherol (500 mg kg^?1), δ‐tocopherol (500 mg kg^?1) or a mixture of α‐, β‐, γ‐ and δ‐tocopherols (250 mg kg^?1 each) and heated under the same conditions. Losses of tocopherols and formation of polymeric triacylglycerols were followed. Total polar compounds were also evaluated after 10 h of heating. Results demonstrated that tocopherols were lost very rapidly, in the expected order, with α‐tocopherol being the least stable. Polymeric and polar compound formation during heating was inhibited to a variable extent, being more dependent on the natural content and type of tocopherols than on the degree of unsaturation of the oil. For example, polymeric and polar compound contents in soybean oil were significantly lower than those found in high‐linoleic sunflower oil. However, the expected influence of the degree of unsaturation was evident when oils were unprotected or possessed identical initial antioxidant contents. Finally, levels of degradation compounds after 10 h of heating were not dependent on the remaining content of antioxidants. © 2002 Society of Chemical Industry     

Influence of crude olive leaf juice on rat liver and kidney functions

Crude juice of olive leaves (Kronakii cultivar) was obtained by hydraulic press. The level of polyphenlic compounds in the juice was 215 ppm. An aliquots of the concentrated olive leaf juice, represent 600, 1200 and 2400 ppm as polyphenols and butylated hydroxy toluene (BHT; 200 ppm) were administered to rats daily for 6 weeks by stomach tube. The liver (aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase activities) and kidney (bilirubin, uric acid, creatinine and urea) function tests and serum contents (total lipids, total cholesterol and low and high‐density lipoproteins) were measured to assess the safety limits of the polyphenolic compounds in the olive leaf juice. The data of the aforementioned measurements indicated that the administration of olive leaf juice did not cause any changes in liver and kidney functions. On the contrary, BHT at 200 ppm induced significant increases in the enzyme activities and the serum levels of total lipids, uric acid, urea and creatinine. Microscopical examinations of kidney and liver tissues of rats administered with the phenolic compounds of olive leaf juice had the histological character as that of control rats whilst, the administration of BHT at 200 ppm altered the features of rat liver tissues and severely damaged the rat kidney tissues.     

Chromatic parameters and oxidation indices for edible vegetable oils submitted to thermal oxidation

Peroxide values, TBA numbers and chromatic parameters of edible vegetable oils (olive, sunflower, corn oils) thermally oxidised (75°C, 100°C, 180°C) during 5 days were determined. For calculating chromatic parameters the recommended standard CIE methods and several simplified methods were employed. With olive oil a remarkable change in spectral characteristics occurred as the temperature and time of heating were increased. Thermal autoxidation, as assessed by peroxide value and TBA number, was only observed at 75°C (Schaal oven test). In none of the three types of vegetable oil was the dominant wavelength modified during the course of the heating process. Luminosity and hue angle showed slight increases in olive and sunflower oils. Colour saturation underwent a remarkable decrease in olive oil. From a comparison and a correlation study it is concluded that the simplified methods could be applied only for certain chromatic parameters and types of vegetable oil. For a comprehensive study of the diverse chromatic parameters the standard CIE methods should be applied.     

Superoxide dismutase from hen’s egg yolk can protect fatty acids from peroxidative damage

Superoxide dismutase (SOD, EC1.15.1.1) is a family of enzymes, which remove superoxide anion (O ₂ ^·? ) from the cells of living organisms. The aim of this study was to describe antioxidative properties of SOD with regard to the protection of unsaturated fatty acids (UFA) from peroxidative damage and to compare this effect with butylated hydroxytoluene (BHT). In this experiment, Cu, Zn-SOD from hen’s egg yolk with a mass of 15.59 ± 0.38 kDa and pI 6.58 ± 0.10, 6.41 ± 0.08 and 6.30 ± 0.15 was used to protect fatty acids from peroxidative damage in vegetable oil (sunflower oil and olive oil) during 200 days of storage at different temperatures—4, 20 and 35 °C. Antioxidative properties of SOD and BHT were expressed as the ratio of unsaturated to saturated fatty acids (SFA) in samples after 50, 100 and 200 days of storage as well as the percentage content of selected fatty acids in the examined oils. SOD from egg yolk showed the same or better antioxidant properties with regard to the concentration of linoleic acid (C18:2) contained in sunflower oil and olive oil than the corresponding concentrations of BHT during 200-day storage at 4, 20 and 35 °C. The concentration of linoleic acid (C18:2) in the sample with SOD was significantly higher during storage at 35 °C on day 200. At all storage temperatures, the ratio of SFA to UFA in samples with the addition of SOD was statistically higher than in oils stored without the antioxidant. With regard to linoleic acid (C18:2), SOD proved to be a better antioxidant than BHT. The results demonstrated better antioxidant properties of SOD from hen’s eggs compared with the same concentrations of BHT at elevated temperatures (at 20 and 35 °C) in oil with a high content of UFA. No negative antioxidative effect (worse than that of BHT at a corresponding concentration) of the addition of SOD from egg yolk on fatty acid composition of the tested samples was observed. Though further research is necessary, SOD from hen’s egg yolk seems to be a promising natural antioxidant of vegetable oils.     

Stability of hydroxycinnamic acids and caffeine from green coffee extracts after heating in food model systems

This study was designed to characterize the stability of hydroxycinnamic acids and caffeine obtained from green coffee beans in the form of lyophilized extract (GCE) during heating after supplementation to model systems with saccharose, potato starch, egg white protein, and sunflower oil. Also the addition of iron ions was used. Systems were prepared as a mixture of GCE with a single substance or in a more complex matrix. Heating was carried out at 180 °C for 0.5 and 1 h. Because of the saccharose content, some systems were heated only at 110 °C. The losses of hydroxycinnamic acids in heated systems ranged from 18 to 84 %, and the caffeine from 1.5 to 10 %. The presence of sunflower oil in the systems had the greatest influence on hydroxycinnamic acids degradation. However, in case of the system of each of the examined substances with the coffee preparation, an increased degradation of hydroxycinnamic acids resulting from the introduction of ferrous ions into the systems was observed. Earlier results concerning antioxidant activity of systems containing GCE allow to conclude that the degradation of hydroxycinnamic acids was weakly related to the decrease in antioxidant activity.     

富勒烯[C60] 作为油脂抗氧化剂的研究

研究富勒烯[C60]对油脂的抗氧化效果。通过烘箱加热法研究富勒烯[C60]与叔丁基对苯二酚(TBHQ)、二丁基羟基甲苯(BHT)、没食子酸丙酯(PG)、V_E对橄榄油、文冠果油、亚麻籽油和猪油的过氧化值和防护因子PF20的影响并进行加热实验。结果表明,在亚麻籽油和文冠果油中的抗氧化效果为:TBHQ富勒烯[C60]PGBHTV_E;在橄榄油中的抗氧化效果为:富勒烯[C60]TBHQPGBHTV_E;在猪油中的抗氧化效果为:TBHQPGBHT富勒烯[C60]V_E。在加热实验中,添加抗氧化剂的油脂均没有析出物且色值不发生变化。表明富勒烯[C60]在油脂中具有很好的抗氧化性能,可作为食品加工、生产与储存中油脂的抗氧化剂。     

Stabilization of sunflower oil by pennyroyal (Mentha piperita) extracts during accelerated storage

The aim of this study was to examine the antioxidant activity of pennyroyal (Mentha piperita) extracts of sunflower oil as a replacement for synthetic antioxidant. This study was performed in two stages. In the current study, it was proven that the examined pennyroyal was in all ways similar to Mentha piperita sequence and its blast performance at the National Center for Biotechnology Information (NCBI). The anti-oxidation activities of Mentha piperita extracts were identified using 2,2-diphenyl-1-picrylhydrazyl and total phenolic content. The protective effect of extracts on the stabilization of sunflower oil was tested and compared with tertiary butyl hydroquinone by measuring peroxide values (y₁), p-anisidine (y₂), and rancimat value (y₃) during storage for 4 weeks at 60°C (Schaal test).The results showed that the antioxidant activity of Mentha piperita extracts (500 ppm) was equal with tertiary butyl hydroquinone effect (100 ppm) at 60°C. In the next step, the sunflower oil containing Mentha piperita extracts (500 ppm) and tertiary butyl hydroquinone (100 ppm) as two blocks were tested to determinate the optimum condition of both high temperature (x₁:180–220°C) and time (x₂: 5–15 min) variables on oxidative stability. The optimum conditions were optimized using response surface methodology. The analysis of variance result showed that temperature and time had significant effects on peroxide, p-anisidine, and rancimat values (p < 0.01). The optimal condition for the examined parameters was related to a sunflower oil treatment containing Mentha piperita extracts (500 ppm) at 180°C and 5 min (with the desirability of 92.1%).     

The influence of phenolic extracts obtained from the olive plant (cvs. Picual and Kronakii), on the stability of sunflower oil

Summary The phenolic compounds of olive cultivars (Picual and Kronakii) were extracted. The total phenolic content of the extracts was estimated and their ability to reduce the oxidation of sunflower oil was tested at 100 °C by using a Rancimat^®. The fruits, leaves and pomaces were extracted separately with ethanol. Portions of the fruits were crushed to produce an oil/aqueous mixture, which was separated and the two fractions further processed. The oil fraction was extracted with 60% aqueous methanol and was separated further, by the method of Dabrowski & Sosulski (1984 ), into three major fractions. These contained mainly free phenols, soluble phenolic esters or bound phenolic acids, respectively. The phenolic concentrations were measured in all the fractions and were in accordance with expected amounts. When tested at 100, 200 or 400 ppm for their ability to stabilize sunflower oil the results showed that the vast majority of the anti‐oxidant activity found in the ‘total phenols’ fraction was because of a ‘free phenolic’ group. The free phenolics, at a 400‐ppm level, exhibited remarkable anti‐oxidant activity and were superior to that of butylated hydroxy toluene (BHT) in retarding sunflower oil oxidative rancidity. The mode of action is discussed.     

Phenolic and antioxidant potential of olive oil mill wastes

Olive oil mill waste was subjected to conventional liquid solvent extraction and supercritical fluid extraction using different solvents and carbon dioxide, respectively. The optimum solvent extraction conditions of phenols were 180 min using ethanol, at a solvent to sample ratio 5:1 v/w, and at pH 2. Solvent and SFE extracts were tested for their antioxidant activity by the DPPH radical scavenging method and by determination of peroxide value on virgin olive oil and sunflower oil. The ethanol extract exhibited the highest antiradical activity, and no correlation was found between antiradical activity and phenol content. The SFE extract exerted good antioxidant capacity although its phenolic yield was not quite high. Moreover, the ethanol extract appeared to be a stronger antioxidant than BHT, ascorbyl palmitate and vitamin E by the Rancimat method on sunflower oil. HPLC analysis of the extracts showed that the predominant phenolic compound was hydroxytyrosol. Various phenolic acids and flavonoids were also identified.     

Effect of plant sterols on the rate of deterioration of heated oils

Three different plant sterol fractions were added to refined cottonseed oil. The first fraction was isolated from olive oil, the second fraction Δ⁵-avenasterol was extracted from the green algae (Ulva lactuca) and the third fraction was a sterol mixture, made up chiefly of β-sitosterol. Cottonseed oil with the different sterols added was heated at 180±5°C and the rate of oxidation followed by changes in the composition and in physical constants. Olive oil sterol mixtures containing Δ⁵-avenasterol and Δ⁵-avenasterol alone reduced the extent of oxidation. β-sitosterol was initially ineffective and became slightly prooxidant after prolonged heating.     

Temperature dependence of the autoxidation and antioxidants of soybean, sunflower, and olive oil

Effects of temperature on the autoxidation and antioxidants changes of soybean, sunflower, and olive oils were studied. The oils were oxidized in the dark at 25, 40, 60, and 80 °C. The oil oxidation was determined by peroxide (POV) and p-anisidine values (PAV). Polyphenols and tocopherols in the oils were also monitored. The oxidation of oils increased with the oxidation time and temperature. Induction period decreased with the oxidation temperature; 87 and 3.6 days at 25 and 60 °C, respectively, for sunflower oil. The activation energies for the autoxidation of soybean, sunflower, and olive oils were 17.6, 19.0, and 12.5 kcal/mol, respectively. Olive oil contained polyphenols at 180.8 ppm, and tocopherols were present at 687, 290, and 104 ppm in soybean, sunflower, and olive oils, respectively. Antioxidants were degraded during the oil autoxidation and the degradation rates increased with the oxidation temperature of oils; for tocopherols, 2.1 × 10⁻³ and 8.9 × 10⁻²%/day at 25 and 60 °C, respectively, in soybean oil.     

Stabilization of Sunflower Oil During Accelerated Storage: Use of Basil Extract as a Potential Alternative to Synthetic Antioxidants

The antioxidant efficacy of basil extracts was estimated in stabilization of sunflower oil. The basil essential oil was analyzed by gas chromatography–mass spectrometry. Twenty-two compounds were identified representing 93.74% of the total essential oil. Basil methanolic extract was thermally evaluated by heating at 185°C. At the 100 min heating time, the extract exhibited antioxidant activity higher than that of butylated hydroxytoluene. Different concentrations of methanolic extract were added to sunflower oil. Selected parameters (i.e., weight gain, induction period to primary oil oxidation, peroxide value, conjugated dienes, and conjugated trienes) were considered for evaluating the effectiveness of basil in stabilization of sunflower oil. Basil methanolic extract showed good antioxidant activity according to synthetic antioxidants. Basil may be used as a natural antioxidants to prevent vegetable oils oxidation.     

The use of polyphenolic extract,purified hydroxytyrosol and 3,4-dihydroxyphenyl acetic acid from olive mill wastewater for the stabilization of refined oils: a potential alternative to synthetic antioxidants

Ethyl acetate extracts of olive mill waste water (OMWW) were prepared, under in optimal conditions, using a continuous counter-current extraction unit. The antiradical and antioxidant activities of the OMWW extract as well as pure phenolic compounds identified in this extract were evaluated. Results showed that pure hydroxytyrosol and 3,4-dihydroxyphenyl acetic acid had the highest radical-scavenging effects on 1,1-diphenyl-2-picrylhydrazyl radical and the highest antioxidant activities using the β-carotene linoleate model system.The effect of addition of individual phenolic compounds and OMWW extract to refined olive and husk oils was compared with that of control, BHA and BHT at 50 °C. Unexpectedly, 3,4-dihydroxyphenyl acetic acid had the highest protective effect against oil oxidation. Oils with added 3,4-dihydroxyphenyl acetic acid had lower PV than oils with added hydroxytyrosol, the most studied powerful antioxidant. Moreover, the addition of OMWW extract, at 500 ppm, resulted in lower PV values than BHA, p-hydroxyphenylacetic acid, tyrosol on the control.The results suggested that 3,4-dihydroxyphenyl acetic acid, hydroxytyrosol and OMWW extract possess useful antioxidant properties and may be used as alternatives in the search for natural replacement of synthetic antioxidant food additives.     

The antioxidants in oils heated at frying temperature,whether natural or added,could protect against postprandial oxidative stress in obese people

We have investigated the effects of the intake of oils heated at frying temperature in order to find an oil model for deep-frying that prevents postprandial oxidative stress. Twenty obese people received four breakfasts following a randomised crossover design consisting of different oils (virgin olive oil (VOO), sunflower oil (SFO), and a mixed seed oil (SFO/canola oil) with added dimethylpolysiloxane (SOX) or natural antioxidants from olives (SOP)), which were subjected to 20 heating cycles. The intake of SFO-breakfast reduced plasma GSH levels and the GSH/GSSG ratio, increased protein carbonyl levels, and induced a higher gene expression of the different NADPH-oxidase subunits, Nrf2-Keap1 activation, gene expression of the antioxidant enzymes in peripheral blood mononuclear cells and antioxidant plasma activities than the intake of the breakfasts prepared with VOO, SOP and SOX. Oils with phenolic compounds, whether natural (VOO) or artificially added (SOP), or with artificial antioxidant (SOX), could reduce postprandial oxidative stress compared with sunflower oil.     

Effect of plant extracts on the oxidative stability of sunflower oil and emulsion

The antioxidative activities of six plant extracts (catnip, hyssop, lemon balm, oregano, sage and thyme) were evaluated in sunflower oil and its 20% oil-in-water emulsion in the dark at 60°C. The oxidation process was followed by measuring the formation of primary (conjugated diene hydroperoxides) and secondary (volatile compounds) oxidation products. Sage extracts (600 and 1200 ppm) effectively inhibited the formation of conjugated dienes and volatile compounds (hexanal and pentanal) in oil and emulsion and showed the highest antioxidative activity compared with 300 ppm BHT. Thyme and lemon balm extracts inhibited hexanal generation more than formation of conjugated dienes in both oil and emulsion. Oregano extract was more active in oil than in emulsion. Catnip and hyssop extracts (600 ppm) showed prooxidative action to sunflower oil at 60°C. These two extracts increased the formation of conjugated dienes compared with the control oil. In emulsions, catnip extract (600 ppm) was active and significantly inhibited the formation of conjugated dienes more than BHT (300 ppm) during additional incubation.     

Storage Stability of Phenolic-Fortified Avocado Oil Encapsulated Using Different Polymer Formulations and Co-extrusion Technology

This study compares the stability and phenolic contents of avocado oil fortified with phloridzin (at 300?ppm) and encapsulated with alginate or the combination of alginate and hydroxypropyl methylcellulose (HPMC) (at a ratio of 3:1), over a 90-day storage period at 37°C. The storage stability of unencapsulated avocado oil (control), and encapsulated oils without any added antioxidant, or with butylated hydroxytoluene (BHT) were also examined for comparison. Results of peroxide value, p-anisidine value, Totox value, free fatty acid and extractable phenolic content analyses suggest that the combined use of encapsulation and an antioxidant (BHT or phloridzin) were synergistically beneficial for improving the oxidative stability and suppressing hydrolytic rancidity of avocado oil at 37°C. Alginate alone was a better encapsulant for avocado oil than the combination of alginate and HPMC, which was supported by the results of optical and environmental scanning electron microscopy examinations which showed that alginate beads were bigger and stronger than alginate?CHPMC beads. The finding that phloridzin was still significantly retained in the encapsulated oil after the 90-day storage indicated that the final encapsulated oil product possessed additional nutritional values derived from this phenolic antioxidant. Thus, both the encapsulant polymer matrix and the types of added antioxidant are ultimately important when using the antioxidant fortification and oil encapsulation approaches for tackling oil stability issues.     

THERMAL STABILITY OF SOME COMMERCIAL NATURAL AND SYNTHETIC ANTIOXIDANTS AND THEIR MIXTURES

The thermal stability of some commercially available antioxidants alone or in binary or ternary mixtures was investigated in order to find the optimal combination of antioxidants for food processing. The synthetic antioxidants used were butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG) and tertiary-butyhydroquinone (TBHQ). Other antioxidants such as ascorbyl palmitate (AP), mixed tocopherols (TOCO) and monoacylglycerol citrate (MGC) were also employed. The effectiveness of these antioxidants and their combinations was assessed using the Rancimat test by measuring the induction period for the oxidation of sunflower oil after heating at 180C for 1 h and comparing it to the oxidation kinetics of the oil without added antioxidants. All antioxidants and their binary or ternary mixtures showed different degrees of thermal instability. TBHQ individually, among all the examined antioxidants, showed the highest thermal stability. On the other hand, AP as an antioxidant in sunflower oil exhibited low stability during heating. The thermal stability of AP could be enhanced by the addtion of BHA or BHT in binary mixtures at a ratio of 1:3 (w/w). In addition, the ternary mixture of AP, TOCO and MGC (65:25:10) in sunflower oil also showed a higher stability to thermal inactivation. However, the ternary mixture containing 0.13% AP, 0.05% TBHQ and 0.02% MGC provided the optimal protection during thermal treatment. Although a combination of 0.13% BHT, 0.05% AP and 0.02% MG was very effective synergistically at room temperature, it showed a higher susceptibility to thermal inactivation. It was