The effect of primary antioxidants and synergists on the activity of plant extracts in lard

The antioxidant activities of combinations of plant extracts and primary antioxidants or citric acid were studied in lard stored at 75°C. Methanol extracts of oregano, thyme, marjoram, dittany, rosemary and sage were used. When combined with butylated hydroxyanisole, butylated hydroxytoluene or ascorbyl palmitate the extracts showed an additive antioxidant effect, while combinations with propyl gallate did not increase the induction period obtained by the phenolic antioxidant. Negative synergism was observed when the plant extracts were mixed with DL-α-tocopherol. Citric acid showed a high synergistic efficiency with marjoram extract and a minor one with thyme extract, but it had a negative effect with all the others. Ternary mixtures of the plant extracts with citric acid and ascorbyl palmitate had lower activity than the corresponding dual combinations with ascorbyl palmitate, except for the mixture of marjoram extract.     

Extraction and identification of antioxidants from the spice Aframomum danielli

Successive extractions with diethyl ether and methanol of the whole seeds of the spice Aframomum danielli yielded diethyl ether extract (ADEE), 13.9%, and methanol extract (ADM), 3.4%, respectively. Similarly, reextraction of the defatted seeds of A. danielli successively with diethyl ether and methanol yielded extracts DFADEE (7.9%) and DFADM (6.7%), respectively. When these extracts were added to refined peanut oil (PNO) at 200 ppm, they showed good antioxidative effects. The percentage antioxidant effectiveness (AE) values were as follows: DFADM (87.3) > ADM (85.3) > ADEE (83.4)=tert-butyl hydroquinone (83.4) on day 20 of storage in an oven maintained at 65±1°C. Generally, antioxidant extracts prepared from A. danielli were also more effective than butylated hydroxytoluene and α-tocopherol in stabilizing refined PNO. Antioxidant components of A. danielli were tentatively identified as phenolic compounds of the trihydroxy type with reducing properties. All extracts prepared from A. danielli showed strong ultraviolet-absorbing characteristics, and methanol was a good extracting solvent.     

MgO-CaO-C砖用抗氧化剂的研究

在MgO－CaO－C砖中分别加入3％B4C、BN、ZrB2和A1，在1O00℃，2h、1400℃，2h和1500℃，0.5h下，于空气中进行氧化试验。试验结果表明，B4C是一种非常优异和理想的抗氧化剂。进一步试验还说明，MgO－CaO－C砖中加入1％B4C其抗氧化效果已很明显。     

Phase formation in MgO-C refractories with different antioxidants

The application of Al or Si as antioxidants in MgO-C refractories leads to the in situ formation of new phases. Due to uncertainties regarding phase formation in some references four different test series were heat treated from 800 to 1600 °C under reducing conditions in 200 °C steps. The antioxidant systems investigated were pure Al, Al and Si in two different ratios and SiC. The addition of SiC did not lead to the formation of new phases but in case of Al and Si addition carbides, nitrides, oxycarbonitrides and oxynitrides were formed. The reaction series, its reason and its relation to equilibrium phase composition have been revealed.     

Alkylated phenolic antioxidants for paints

Summary  Polymeric antioxidants based on p-cumyl phenol formaldehyde resin (PCPF), p-nonyl phenol formaldehyde (PNPF) and p-octyl phenol formaldehyde (POPF) were prepared by condensation reaction of respective phenols with formaldehyde in presence of an acid catalyst. The reactions were monitored by TLC and the melting point of the products was determined by open capillary method. Stabilising the action of PCPF, PNPF for protecting paint against thermal oxidation was tested using a QUV weatherometer. The effect of exposure on the properties of paints such as gloss, whiteness and yellowness were evaluated. Results show that paints containing these new polymeric antioxidants possess better stabilising effects against photo-oxidation than those employed in standard paints available in the market.     

Identification and function of antioxidants from oat groats and hulls

Antioxidant components of methanolic extracts of groats and hulls from Ogle oats were identified and quantified by using gas chromatography-mass spectrometry (GC-MS) and gas chromatography after N,O-bis(trimethylsilyl)acetamide derivatization. Ferulic, p-coumaric, vanillic, p-hydroxybenzoic, 4-hydroxyphenylacetic acids and vanillin and catechol were quantified in groat and hull extracts. Additionally, caffeic acid in groat extracts, and o-coumaric, sinapic and slaicylic acids in hull extracts were quantified. Extracts from groats and hulls at levels of 0.05, 0.1, 0.2, and 0.3% w/w, based on total phenolic content, were added to soybean oil, and their antioxidant effectiveness was compared with that of 0.02% w/w tertiary butylhydroquinone (TBHQ) and a control (no additives) at 60°C in the dark by measuring peroxide values. Antioxidant activities of both extract sources increased with increased concentration. During 20 d of storage, the groat extract (0.3%) was not significantly different from TBHQ after day 16, and hull extracts (0.2 and 0.3%) were not significantly different from TBHQ on day 20. Oils containing pure phenolics at the same concentrations measured in the groat and hull extracts oxidized more quickly than did oils containing the extracts.     

Oregano flavonoids as lipid antioxidants

Oregano (Origanum vulgare L.) leaves were successively extracted with hexane, ethyl ether, ethyl acetate and ethanol. The ethanol extract was reextracted in a separatory funnel with petroleum ether, ethyl ether, ethyl acetate and butanol. The ethyl ether layer was the most effective in stabilizing lard against oxidation, with activity equal to butylated hydroxytoluene. It also showed antioxidant activity when tested on vegetable oils under storage or frying conditions. The main antioxidant factors isolated from the ethyl ether layer consisted of flavonoids. Chromatographic and spectrophotometric analysis demonstrated the presence of the flavone apigenin, the flavanone, eriodictyol and the dihydroflavonols, dihydrokaempferol and dihydroquercetin.     

The impact of antioxidants on biodiesel oxidation stability

The potential of 11 different synthetic phenolic antioxidants to improve the oxidation stability of biodiesel prepared from different feedstocks was investigated. Measurements of oxidation stability were carried out according to the European biodiesel specifications with a Rancimat instrument at 110 °C. At antioxidant concentrations of 1000 mg/kg, an improvement in oxidation stability could be achieved with all antioxidants tested. Especially the antioxidants DTBHQ, IONOX 220, Vulkanox ZKF, Vulkanox BKF, and Baynox were able to significantly improve the oxidation stability, leading to stabilization factors between 1.89 and 13.07. Variation of antioxidant concentrations between 100 and 1000 mg/kg showed that the efficiency of the antioxidants varied depending on the different types of biodiesel. When used as additives, Baynox showed good effects on rapeseed oil methyl ester (RME) stability, DBHQ on recycled cooking oil methyl ester (RCOME) stability, Vulkanox BKF on distilled RCOME (DRCOME) stability, and IONOX 220 on tallow methyl ester (TME) stability. Evaluation of the influence of the antioxidants on critical biodiesel fuel parameters showed no negative impacts on viscosities, densities, carbon residues, CFPP, and sulphated ash contents of the different biodiesel samples. However, in terms of acid values, a noticeable increase could be observed at antioxidant levels of 1000 mg/kg. At lower antioxidant concentrations, this increase was much lower and the values remained within the required limits.     

Stabilization of phytosterols in rapeseed oil by natural antioxidants during heating

Antioxidants are substances that can reduce negative changes in fat. Many antioxidants are very effective during storage, but during heating they lose their properties. It is very important to find antioxidants that will be stable at high temperatures and protect fat throughout the entire frying process. The aim of this study was to estimate the effect of natural and synthetic antioxidants on changes in phytosterols of rapeseed oil during heating. Oil with antioxidants was heated at 180 °C for 4 h in a Rancimat® and in an Oxidograph®. Ethanol extract of rosemary, ethanol extract of green tea, and BHT were used in the study. The contents of phytosterols (sitosterol, campesterol, avenasterol, brassicasterol, stigmasterol) and oxyphytosterols (7α‐ and 7β‐hydroxysterol, 5α,6α‐ and 5β,6β‐epoxysterol, 7‐ketosterol and triols) were estimated by gas chromatography. In all samples with antioxidants, a lower decrease of phytosterols and a lower increase of total oxyphytosterols were observed in comparison with the control sample (without antioxidant). The antioxidant effect depends on the type of the antioxidant and the heating conditions. The best results were observed in samples with natural antioxidants. BHT was a substance that protected phytosterols as well, but not as effectively as the other antioxidants.     

Effects of antioxidants and humidity on the oxidative stability of microencapsulated fish oil

The effects of various antioxidants and RH on the oxidative stability of microencapsulated fish oil powder were investigated using PV and thiobarbituric acid tests. The micorencapsulation process provided high encapsulation efficiency (≥88% of extractable fish oil). Without antioxidants, the encapsulated fat was 10 times more stable against oxidation than the surface fat, as determined by PV. α-Tocopherol, which is a lipophilic antioxidant, showed a greater antioxidative effect in both surface and encapsulated fats than ascorbyl palmitate, which is an amphiphilic antioxidant. According to TBARS values, the longest lag period was observed at 0% RH. Addition of >200 ppm α-tocopherol in a 10–30% RH range prolonged the oxidative stability of the microencapsulated fish oil powder.     

Agilent provides fast identification of antioxidants in plastics

Agilent Technologies Inc has devised a method based on advanced chromatography that allows rapid identification of antioxidant additives and their degradation products in plastics formulations. The company believes this will aid in developing plastic products with better performance.This is a short news story only. Visit www.adcomp.com.com for the latest additives and compounding industry news.     

地木耳活性成分的提取及其护肤功效研究

为探索天然植物提取物美容护肤的功效,研究了地木耳Nostoc commune Vauch.（普通念珠藻）醇提物和水提物的抗氧化、保湿和防晒效果。结果表明,地木耳提取物对羟自由基（·OH）和过氧化氢（H2O2）具有良好的清除能力,且失水率低、紫外线吸收能力强,具有良好的抗氧化、保湿和紫外线防护效果。不同品系地木耳的提取物在抗氧化、保湿和抗紫外线效果上无显著性差异,醇提物的效果略优于水提物。     

Effect of different antioxidants on lycopene degradation in oil‐in‐water emulsions

There is interest in incorporating lycopene into foods because it is a natural pigment and can also play a role in preventing disease. Therefore, the effect of the addition of various antioxidants in lycopene containing oil‐in‐water emulsions stabilized with Tween 20 at acidic pH was studied in order to determine protection systems against lycopene oxidation. In this model, EDTA showed pro‐oxidant activity while other chelators like citric acid and tripolyphosphate showed no effect. The free radical scavengers, propyl gallate (PG), gallic acid (GA), and α‐tocopherol all had the ability to decrease lycopene oxidation with α‐tocopherol being the most effective. The combination of 1 µM α‐tocopherol and 10 µM GA was more effective than the individual antioxidants. Addition of ascorbic acid to the combination of α‐tocopherol and GA system accelerated lycopene loss. These results suggest that by the proper selection of free radical scavenging antioxidants, lycopene stability in oil‐in‐water emulsions could be significantly improved. Practical applications: Evidence that dietary lycopene decreases the risk for a number of health conditions has generated new opportunities for addition of lycopene to functional foods. A successful strategy to deliver lycopene into foods is by means of oil‐in‐water emulsions. However, lycopene may decompose thus causing nutritional loss and color fading. In order to prevent this, the effectiveness of various antioxidants and their combinations in Tween 20 stabilized oil‐in‐water emulsions was studied. Overall, lycopene oxidation in oil‐in‐water emulsions could be significantly reduced by the proper selection of free radical scavengers. This fact is of interest to food industry for increasing the shelf‐life of lycopene containing functional foods where the lycopene is dispersed in the food in the form of an oil‐in‐water emulsion.     

Singlet oxygen oxidation of lipids resulting from photochemical sensitizers in the presence of antioxidants

Singlet oxygen produced by photochemical sensitizers may play an important role in the oxidation of lipids in foods. Therefore, we studied the singlet oxygen oxidation of lipids and the scavenging ability of antioxidants. Singlet oxygen was generated using the photosensitizer rose bengal. The oxidation products of lipids and antioxidants were separated by high-performance liquid chromatography and monitored using post-column chemiluminescence and/or iodometric detection. The competitive reaction rates of various antioxidants and lipids were studied to elucidate the roles played by antioxidants in the prevention of food oxidation by singlet oxygen.     

The influence of antioxidants on the oxidation stability of biodiesel

Oxidation stability of bodiesel is an important issue because FA derivatives are more sensitive to oxidative degradation than mineral fuel. Therefore, in the most recent European Specifications for biodiesel, a minimum value of 6 h for the induction period at 110°C, measured with a Rancimat instrument, is specified. To guarantee this value at the filling station, the use of additional antioxidants will be necessary. In this paper we show the influence of different synthetic and natural antioxidants on the oxidation stability, using the specified test method. Biodiesel produced from rapeseed oil, sunflower oil, used frying oil, and beef tallow, both undistilled and distilled, was investigated. The four synthetic antioxidants pyrogallol (PY), propylgallate (PG), TBHQ, and BHA produced the greatest enhancement of the induction period. These four compounds and the widely used BHT were selected for further studies at concentrations from 100 to 1000 mg/kg. The induction periods of methyl esters from rapeseed, oil, used frying oil, and tallow could be improved significantly with PY, PG, and TBHQ, whereas BHT was not very effective. A good correlation was found between the improvement of the oxidation stability and the FA composition.     

Natural polyphenols as chain‐breaking antioxidants during methyl linoleate peroxidation

A technique based on monitoring oxygen consumption was applied to study 11 natural and model polyphenols (PP, QH₂) as well as four typical monophenolics as a chain‐breaking antioxidant during the controlled chain oxidation of methyl linoleate (ML) in bulk at 37°C. The antioxidant activities of QH₂ were characterized by two parameters: the rate constant k₁ for reaction of QH₂ with the peroxy radical ${\rm LO}_{2}^{{\bf .}} $ : (i) QH₂ + ${\rm LO}_{2}^{{\bf .}} $ → ${\rm QH}^{{\bf .}} $ + LOOH and the stoichiometric factor of inhibition, f, which shows how many kinetic chains may be terminated by one molecule of QH₂. The rate constant k₁ were reduced significantly by factor of 4 –28 as compared to these determined during the oxidation of styrene in bulk; the effect was typically more pronounced for catechol derivatives than for pyrogallol derivatives. At the same time, f for QH₂ was found to be close to two independent of the number of active OH groups, similar to that determined earlier during the inhibited oxidation of styrene. The formation of H bond between OH group of QH₂ and carboxyl group of ML is suggested as a reason for reducing effect of ML on k₁. Practical applications : This work reports rate constants for the reaction of lipid peroxyl radical with phenolics and stoichiometric coefficient of inhibition, which characterize the antioxidant activity (AOA) of 15 natural and model PP, QH₂ during the controlled peroxidation of ML. The reactivity of PP, QH₂ during the oxidation of ML is routinely lower than the reactivity during the oxidation of non‐polar model hydrocarbons. This information may be useful to estimate the AOA of natural PP, QH₂ in real systems of practical significance including plant oils, fats, food‐stuffs, biological objects, and similar.     

Optimization of physicochemical changes of palm olein with phytochemical antioxidants during deep-fat frying

Response surface methodology (RSM) was used to optimize the amounts of rosemary and sage extracts together with citric acid as synergist antioxidants in stabilizing refined, bleached, and deodorized palm olein during repeated deep-fat frying of potato chips. For all physicochemical properties studied, these phytochemical antioxidant treatments significantly (P<0.05) reduced the oxidation rate of the oil. During 5 d of frying, anisidine value, peroxide value, free fatty acid, polymer content, color units, viscosity, and absorbances at 232 and 268 nm gradually increased, whereas iodine value and ratio of 18∶2/16∶0 decreased. Further statistical analyses, including coefficient of determination (R ²) and probability of F values, indicated that mathematical models for each physicochemical parameter could be developed confidently in this study, with R ² for all parameters greater than 0.90. These results suggested that an optimal mixture of phytochemical antioxidants derived from rosemary and sage together with citric acid could be produced using RSM for stabilizing thermally processed oil. For many physicochemical parameters examined, the use of moderate levels of antioxidants could result in optimal responses.     

Supercritical extraction of borage seed oil coupled to conventional solvent extraction of antioxidants

This paper describes the extraction of borage seed oil by supercritical carbon dioxide (SC-CO₂) and the further extraction of antioxidants from the SC-CO₂-defatted borage meal with organic solvents (water, methanol, ethanol and ethyl acetate). The optimal conditions for oil extraction were obtained at 303 and 323 K at 200 bar, 2.5 h and a continuous flow of CO₂ of 1.5 L/h introduced through the bottom when the operating pressure and temperature were reached, attaining a yield of 60%. Borage oil is rich in unsaturated fatty acids; oleic acid, linoleic acid and linolenic acid accounted for 74% of the total fatty acid content under the above conditions. The highest extraction yield was achieved using water or methanol as extracting solvent from the SC-CO₂-defatted borage meal at 303 K and pressures of 200 and 150 bar for water and methanol, respectively. The most potent extracts, according to all methods tested, were obtained with water and methanol.