The changes of Trp-deficient linusorb during the oxidation and the influence ofγ-tocopherol on their oxidative stability

Linusorbs(LOs),particularly the Methionine(Met)-containing yet Tryptophan(Trp)-free LO(CLB and CLP),play a significant role in shaping the quality and sensory attributes of flaxseed oil.To investigate the stability of these LOs and their oxidized forms during accelerated oxidation,the polar fractions of crude flaxseed oil were selectively removed using silica absorption and then reintroduced separately into the oil matrix along with LOs andγ-tocopherol(γ-T).Through comprehensive analysis of oxidative stability indexes,LOs content changes,oxidation kinetics,and the correlation between LOs and oxidative stability indexes,we observed that the LOs fraction alone exhibited a moderate antioxidant effect on the peroxide value(PV)but a weaker effect on the panisidine value(p-AV)of flaxseed oil.However,upon addition ofγ-T,we observed a weak synergistic effect betweenγ-T and LOs in suppressing PV,while a stronger effect in suppressing p-AV.Additionally,a comparison of the oxidation kinetics of different LOs indicated thatγ-T preferentially protected the oxidation of CLP over CLB.Similar protective trends ofγ-T towards the methionine sulfoxide(MetO)and methionine sulfoxide(MetO2)form of LOs were also observed,albeit to a lesser extent.Correlation analysis revealed that changes in Metcontaining LOs,particularly CLP,showed a high correlation with PV in the tested matrices,while MetOcontaining LOs better depicted changes in p-AV.Importantly,CLP demonstrated higher susceptibility to the influence of antioxidants,making it more suitable for evaluating the peroxide value in flaxseed oil samples.

Effect of laccase from Trametes versicolor on the oxidative stability of edible vegetable oils

The increasing demand of natural food from consumers has limited the use of traditional methods to control the oxidation of lipids,such as synthetic antioxidants and hydrogenation.Besides,it has been reported that the use of enzymes is efficient to eliminate dissolved oxygen in foods such as vegetable oils.Laccase is a polyphenol oxidase and the reduction of oxygen to water is accompanied by the oxidation,typically,of a phenolic substrate.Laccase have become important,industrially relevant enzymes that can be used for a number of diverse applications such waste detoxification,textile dye transformation,food technologic uses,biosensor and analytical applications,bioethanol production,among others.The target of this study was to evaluate the effect of laccase enzyme from Trametes versicolor,on the oxidative stability of sesame,chia,peanut and sunflower oils,measured through the peroxide value(PV)and conjugated dienes(K232)and trienes(K270).The samples of oil with laccase showed higher PV,K232 and K270 than their corresponding controls,under the conditions evaluated(room temperature and 60◦C).The results suggest that fungal laccase has an unexpected pro-oxidant effect on vegetable oils,possibly promoted by products derived from the oxidation of phenols by enzymatic action.

Fat and Oil Oxidation by Electron Spin Resonance （ESR） Spin-Trapping Method

Oxidation of fats and oils during storage causes their degradation and loss of nutritional value and appearance. Electron spin resonance （ESR） is the only method that can be used to directly observe the radicals. In this study, the authors used an ESR spin-trapping method to study the oxidation of triacylglycerols （TAG） containing different fatty acids （FAs） commonly found in food. The ESR adduct signals were analyzed to study the effect of double bonds and the chain length of the FAs of TAG on oxidation. Oxidation was conducted by applying UV irradiation to TAG by dissolving it in N-tert-buthyl〈t-phenylnitrone （PBN）, which trapped the radicals induced in the TAG as an ESR adduct signal. The detection was clearly successful. There were no differences in the spectra of tristearin （18：0） and tripalmitin （16：0）; thus, it can be concluded that the length of the carbon chain of the FAs of TAG does not affect the oxidation reactions. However, the ESR spectra of tristearin （18：0）, triolein （18：1） and trilinolein （18：3） were clearly different due to the presence/absence of a new peak corresponding to new induced radicals, leading to the conclusion that double bonds play a major role in the oxidation reactions of fats and oils.

Effect of Seed Heat-Treatment on the Oxidative Stability of Canola Oil Body Emulsions

Enhancement of oxidative stability of canola oil extracted from seed subjected to prior heat-treatment has been attributed to heat-induced generation of antioxidants from phenolic precursors occurring in canola seed. Dispersion of aqueous extracts of intact seed oil bodies (OBs) in water is a novel and interesting way of producing natural and oxidatively stable food emulsions with minimal use of synthetic antioxidants and emulsifiers. As there is growing interest in natural food emulsions containing unsaturated oils, we investigated whether the oxidative stability of canola OB emulsions could be further improved by subjecting canola seed to heat-treatment prior to oil body extraction. Oil-in-water (5%, w/w) emulsions of OBs extracted from canola seed before and after heat-treatment were considerably more resistant to oxidation than emulsions prepared from refined canola oil and Tween? 40 emulsifier. However, only small amounts (0.9% - 4.5% by weight) of the phenolic compounds present in canola seed were transferred to the OBs after aqueous extraction, and consequently there was no discernible effect on oxidative stability as a result of prior heat-treatment of the seed. Thus, in contrast to oil, there is no oxidative stability benefit to be gained by subjecting canola seed to heat-treatment prior to extraction of OBs.

Impact of deacidification processes on the quality and oxidative stability of walnut oil

In order to select an appropriate deacidification process and improve the quality of walnut oil,low-temperature cold-pressed crude walnut oil was used as raw material.Deacidified walnut oil was prepared using three deacidification processes:chemical deacidification(CD),adsorption deacidification(AD),and molecular distillation deacidification(MDD).The physicochemical properties,nutritional components,and in vitro antioxidant activities of the resulting deacidified walnut oils were comparatively analyzed.The results indicate that the fatty acid content in walnut oil exhibits fluctuating changes during the three different deacidification processes.The MDD shows a higher deacidification rate,reaching 94.06%,which is superior to the other two methods.Additionally,the AD retains more total phenols and tocopherols,with retention rates of 95.79%and 74.62%,respectively;whereas MDD is more effective at retaining phytosterols,achieving a retention rate of 98.09%.All these methods displayed positive impacts on the in vitro antioxidant capacity and oil stability of walnut oil,with ferric-reducing antioxidant power(FRAP)content and oxidative stability time were significantly reduced.-whencompared to the untreated crude oil Among them,AD had the greatest impact on oxidative stability index(OSI),with its decreasing from 2.06 h to 0.82 h.Overall,compared to CD or MDD,the AD has best application prospects in preserving nutritional components.

Effects of dietary Clostridium butyricum and rumen protected fat on meat quality,oxidative stability,and chemical composition of finishing goats

Background Clostridium butyricum(CB)is a probiotic that can regulate intestinal microbial composition and improve meat quality.Rumen protected fat(RPF)has been shown to increase the dietary energy density and provide essential fatty acids.However,it is still unknown whether dietary supplementation with CB and RPF exerts beneficial effects on growth performance and nutritional value of goat meat.This study aimed to investigate the effects of dietary CB and RPF supplementation on growth performance,meat quality,oxidative stability,and meat nutritional value of finishing goats.Thirty-two goats(initial body weight,20.5±0.82 kg)were used in a completely randomized block design with a 2 RPF supplementation(0 vs.30 g/d)×2 CB supplementation(0 vs.1.0 g/d)factorial treatment arrangement.The experiment included a 14-d adaptation and 70-d data and sample collection period.The goats were fed a diet consisted of 400 g/kg peanut seedling and 600 g/kg corn-based concentrate(dry matter basis).Result Interaction between CB and RPF was rarely observed on the variables measured,except that shear force was reduced(P<0.05)by adding CB or RPF alone or their combination;the increased intramuscular fat(IMF)content with adding RPF was more pronounced(P<0.05)with CB than without CB addition.The pH24h(P=0.009),a*values(P=0.007),total antioxidant capacity(P=0.050),glutathione peroxidase activities(P=0.006),concentrations of 18:3(P<0.001),20:5(P=0.003)and total polyunsaturated fatty acids(P=0.048)were increased,whereas the L*values(P<0.001),shear force(P=0.050)and malondialdehyde content(P=0.044)were decreased by adding CB.Furthermore,CB supplementation increased essential amino acid(P=0.027),flavor amino acid(P=0.010)and total amino acid contents(P=0.024)as well as upregulated the expression of lipoprotein lipase(P=0.034)and peroxisome proliferator-activated receptorγ(PPARγ)(P=0.012),and downregulated the expression of stearoyl-CoA desaturase(SCD)(P=0.034).The RPF supplementation increased dry matter intake(P=0.005),averaged daily gain(trend,P=0.058),hot carcass weight(P=0.046),backfat thickness(P=0.006),concentrations of 16:0(P<0.001)and c9-18:1(P=0.002),and decreased the shear force(P<0.001),isoleucine(P=0.049)and lysine content(P=0.003)of meat.In addition,the expressions of acetyl-CoA carboxylase(P=0.003),fatty acid synthase(P=0.038),SCD(P<0.001)and PPARγ(P=0.022)were upregulated due to RPF supplementation,resulting in higher(P<0.001)content of IMF.Conclusions CB and RPF could be fed to goats for improving the growth performance,carcass traits and meat quality,and promote fat deposition by upregulating the expression of lipogenic genes of Longissimus thoracis muscle.

Evaluation and improvement of the oxidative stability of leather fatliquors

Fatliquor oxidation may give leather unpleasant odor,and excessive amounts of Cr(VI)and volatile organic com-pounds.The accurate evaluation and improvement of the oxidative stability of fatliquors are of great significance to high-quality leather manufacturing.We proposed a set of practical methods for evaluating the oxidative stability of fatliquors on the basis of oxidation induction time,change in iodine value(∆IV),and change in acid value(∆AV)under accelerated oxidation conditions(at 100°C with 10 L/h of air).Oxidation induction time is a highly sensitive marker for quantifying the oxidative stability of fatliquors,and∆IV and∆AV that are low cost and easy to operate are useful in evaluating the oxidative stability of fatliquors when the oxidation induction time is less than 22 h.The number of double bonds in fatliquors is an important factor affecting oxidative stability.The sulfation modification of fatliquors that greatly reduces double bonds and the addition of antioxidants,especially butylated hydroxyanisole and butylated hydroxytoluene,markedly improve oxidative stability of fatliquors.

Determination of the oxidative stability of olive oil using an integrated system based on dielectric spectroscopy and computer vision

During storage,olive oil may suffer degradation leading to an inferior quality level when purchased and consumed.Oxidative stability is one of the most important parameters for maintaining the quality of olive oil,which affects its acceptability and market value.The current methods of predicting the oxidative stability of edible oils are costly and time-consuming.The aim of the present research is to demonstrate the use of dielectric spectroscopy integrated with computer vision for determining the oxidative stability index(OSI)of olive oil.The most effective features were selected from the extracted dielectric and visual features for each olive oil sample.Three machine learning techniques were employed to process the raw data to develop an oxidative stability prediction algorithm,including artificial neural network(ANN),support vector machine(SVM)and multiple linear regression(MLR).The predictive models showed a great agreement with the results obtained by the Rancimat instrument that was used as a reference method.The best result for modelling the oxidative stability of olive oil was obtained using SVM technique with the R-value of 0.979.It can be concluded that this new approach may be utilized as a perfect replacement for quicker and cheaper assessment of olive oil oxidation.

Recent progress in the thermal treatment of oilseeds and oil oxidative stability:A review

Oxidative deterioration of vegetable oils is of great importance in the food industry.In China,vegetable oils produced via thermal pretreatment are popular owing to their strong oil flavor and enhanced yield.Here,we review:(i)the currently employed thermal treatment methods of oilseeds before oil extraction;(ii)effects of thermal treatments on the physicochemical properties,contents of minor lipid components,and oxidative stability of vegetable oils;and(iii)Maillard model systems that are related to oil and oilseed chemistry.Among the thermal pretreatment technologies,microwave and infrared radiations are promising,but these are not performed on the same large production scales as roasting.For most oilseeds,thermal treatments increase the yield of extracted oil and content of minor lipid compounds in the oil,such as polyphenols,tocopherols,and phytosterols.In addition,some Maillard reaction products(MRPs)generated by heating oilseeds have been extracted.The presence of both minor lipids and MRPs in the oil confers improved oxidative stability.However,the mechanism or relationship between thermal treatment and oxidative stability is yet to be clearly elucidated because vegetable oil oxidation is dependent on variables such as unsaturation,concentration and types of minor lipid components,MRPs,and the potential synergistic effects of these components.Recently,several Maillard reaction models related to thermally treated oilseeds have been established,suggesting that MRPs play a critical role during oxidation.However,comprehensive identification of antioxidants and the mechanism by which they inhibit oxidation are lacking.Future research can be performed to establish models that would help elucidate the antioxidative mechanisms of MRPs for more oilseeds.Using these models,it will be possible to predict the oil quality after processing,based on the presence of MRPs and oil chemistry.

Quality, fatty acid composition and oxidation stability of ten cold-pressed seed oils

Cold-pressed oils from six herb plant seeds and four woody plant seeds were analyzed and compared for their quality characteristics such as oil, crud protein, shell, and moisture content, fatty acid （FA） compositions and oxidation stability. Results showed that walnut kernel contained the greatest amount of seed oil and safflower seed contained the lowest. Safflower, pumpkin, hemp, camellia and peony seeds had high shell content, their kernel oil content significantly increased after shelling. These oils had significant differences （p〈0.01） in levels of fatty acids and the ratio of n-6：n-3 fatty acids. Camellia, safflower, and flax seed oil contained the highest oleic acid, linoleic acid, and a-linolenic acid respectively. Hemp seed oil was observed in a 3.53：1 ratio of n-6 and n-3 fatty acids. All these ten oils were obviously different in moisture and volatile content, acid value, peroxide value and induction period （IP） （p〈0.01）. IP of peony seed oil was lowest （0.94 h） and almond oil was the highest （14.10 h）. IP of oils negatively correlated with polyunsaturated fatty acids content ^=-0.664, p=0.036）. These studies of ten cold-pressed oils may provide better explanation for their potential health benefits and further developing their commercial value.

Compositional characteristics and oxidative stability of chia seed oil(Salvia hispanica L)

Fatty acid composition and triacylglycerols(TAG)profile of chia seed oil were determined.The main fatty acids present in the tested oil wereα-linolenic acid(Ln,61.1%)>linoleic acid(L,16.6%)>palmitic acid(P,6.7%)>oleic acid(O,6.0%)>stearic acid(S,3.2%).Five major triacylglycerols in chia oil were LnLnLn,LnLLn,LnLnP,LnOLn,and LLLn and these contributed more than 76%to the total.The oxidative stability under autoxidative and photooxidative conditions before and after the removal of their minor components was also determined.In addition,tocols,chlorophylls and carotenoids were measured in the oil.Oil samples were stripped of their minor components by using a facile silicic acid and charcoal in one pot rather than in a column.Storage under Schaal oven condition and photooxidation were also monitored for both crude oil(non-stripped)and stripped oil using stationary phase material.Total tocopherol contents were in the order ofβ−/γ-282.68,δ-47.44,andα-tocopherols 10.94 mg/kg of oil.Stripping removed all the minor components including tocopherols,chlorophylls and carotenoids.Oxidative stability of the tested seed oil was primarily affected by its composition of fatty acids,triacylglycerols,minor components,and storage conditions.

Effect of Biodiesel on Oxidation Stability, Detergency and Antiwear Ability of Diesel Oil

Different contents of biodiesel and petrodiesel were incorporated into diesel engine oils. The oxidative stability, detergency and antiwear performance of the formulated diesel oils were evaluated. The results indicated that, compared with petrodiesel, biodiesel was more liable to promote oxidation degradation of diesel oils, leading to worse oxidative stability, detergency and antiwear ability of the oils.

Oxidative Stability of Green Tea Extract-Enriched Rice Bran Oil During Storage

Adding green tea extract to rice bran oil was expected to improve its oxidative stability,so this study was conducted to investigate oxidative stability of green tea extract-enriched rice bran oil(RBOG) during storage at 60℃ for 15 days compared to rice bran oil(RBO),olive(OL),canola(CN),and grape-seed oil(GS).Acid values did not increase during storage,and the highest value was found for OL.The peroxide values of RBOG,RBO,CN,OL,and GS increased for up to 15 days.The highest average rate constant for the change in peroxide value was found for RBO(0.282).TBARS increased continually during storage of RBOG,RBO,CN,and OL;however,the value increased for up to 9 days and then decreased for GS.The highest average rate constant of change in TBARS was found for CN.Overall,the results suggest that green tea extract improves oxidative stability of rice bran oil.

Antioxidant potential of methanolic extracts and powders of some Cameroonian spices during accelerated storage of soybean oil

The efficacy of methanolic extracts and powders of 12 spices (Pimpinella anisum, Scorodophleuszenkeii, Xy- lopiaparviflora, Eugenia caryophyllus, Fagara leprieurii, Fagara macrophylla, Monodora myristica, Olax subscorpioidea, Xylopiaaethiopica, Allium sativum, Zinziber officinale and Cinnamomum zeylanicum) in stabilizing crude soyabean oil during accelerated storage was assessed. The phytochemical screening revealed the presence of phenols in all the spices except that of Allium sativum. Total phenolic content (TPC) and DPPH radical scavenging activity of the extracts varied significantly (p < 0.01) ranging from 1.34 to17.72 gGAE/100 gand 18.91% to 96.39% respectively. Extract of Zinziber officinale, Olax subscorpioidea, Fagaramacrophylla, Eugenia caryophyllus and Xylopia parviflora, which offered the highest TPC, exhibited superior antioxidant activity with regard to the DPPH. Furthermore, the antioxidant effectiveness of the extracts and powders was assessed using crude soyabean oil (CSO) as the oxidation substrate. CSO samples stabilized with extracts at a concentration of 500 ppm (w/w) and powders at a concentration of 1000 ppm were subjected to accelerated storage (65?C, oven heating, 24 days, 8 h heating cycle per day), and analyzed periodically for the extent of oxidative alterations following the measurement of iodine and peroxide value. CSO + BHT at 200 ppm served as standards besides the control. Results?reveal Zinziberofficinale, Cinnamomum zeylanicum, Scorodophleuszenkerii, Monodora myristica, Xylopiaaethiopica, Allium sativum, Fagara leprieurii extracts and powders and the powder of Pimpinella anisum to be potent antioxidants for stabilization of crude soyabean oil.

Fast Evaluation Peanut Oil Quality by Synchronous Fluorescence Spectroscopy and Statistical Analysis

Peanut oil oxidation was to monitor and quantify combining synchronous fluorescence spectroscopy and chemometrics. Peanut oil was subjected to an accelerated oxidation testing. The spectral and related chemical indicators were caught during oxidation induce testing. Fluorescence spectra were gained for each sample with simultaneous excitation from 200 to 800 nm and the offsets (Δλ) of 10 to 180 nm during the oxidation process. The results showed the induce period (IP) of the peanut oil was 16.45 h. Parallel factor analysis (PARAFAC) was performed to select the best Δλ interval of 70 nm, which spectral data was the most suitable for interval partial least square (iPLS) and synergy interval PLS (siPLS) modeling and forecast. The study presented all interval selection methods had the better results than the global spectrum modelling. iPLS reached the best into 10 intervals with a ratio of prediction to deviation (RPD) of 2.10. siPLS that separated the whole spectrum into 15 intervals and combined the third intervals (282 to 320 nm, 362 to 400 nm, and 761 to 800 nm) had a ratio of RPD of 2.26. The results showed the optimal siPLS model performed a little better than iPLS. The established model lying on interval selection could improve the prediction accuracy. It could provide a quick, accurate method to monitor oil oxidation process.

Improving beef hamburger quality and fatty acid profiles through dietary manipulation and exploitation of fat depot heterogeneity

Background： Hamburger is the most consumed beef product in North America, but lacks in nutritional appeal due to its high fat content and high proportion of saturated fatty acids （SFA）. Objectives of the present study were to improve the FA profiles of hamburgers made with perirenal fat （PRF） and subcutaneous fat （SCF） when feeding steers different diets along with examining differences in sensory attributes and oxidative stability. Diets included a control diet containing 70：30 red clover silage： barley based concentrate, a diet containing sunflower-seed （SS） substituted for barley, and diets containing SS with 15% wheat dried distillers＇ grain with solubles （DDGS-15） or 30% DDGS （DDGS-30）. Hamburgers were made from triceps brachii and either PRF or SCF （80：20 w/w）. Results： Perirenal fat versus SCF hamburgers FA had 14.3% more （P 〈0.05） 18：0, 11.8% less cis （c）9-18：1 （P 〈0.05）, and 1.82% more total trdns （t）-18：1 mainly in the form of tl 1-18：1. During sensory evaluation, PRF versus SCF hamburgers had greater （P 〈0.05） mouth coating, but the difference was less than one panel unit. Examining effects of steer diet within PRF hamburgers, feeding the SS compared to the control diet increased （P 〈0.05） t-18：1 by 2.89% mainly in the form of tl 1-18：1, feeding DGGS-15 diet led to no further changes （P 〉0.05）, but feeding DDGS-30 diet reduced the proportions of （P 〈0.05） of t-18：1 chiefly tl 1-18：1. Feeding SS and DDGS diets had small but significant （P 〈0.05） effects on hamburger sensory attributes and oxidative stability. Conclusions： Feeding high-forage diets including SS and 15% DDGS, and taking advantage of the FA heterogeneity between fat depots offers an opportunity to differentially enhance beef hamburgers with 18：2n-6 biohydrogenation products （Le., t11-18：1） with potential human health benefits without compromising their sensory attributes and oxidative stability during retail display.

A Methodological Approach to Study Almond Oil Stability in Relation to <i>α</i>-Tocopherol Supplementation

The objectives of the present study were to identify a suitable parameter to assess the oil oxidation and to study the possibilities of delaying the oxidation of moderately oxidized unrefined almond oil by adding supplementary amounts of α-tocopherol. Three oil samples, with initial peroxide values of 13.3, 19.5 (moderately oxidized oils), and 28.9 (oxidized oil), were supplemented with 100, 250 and 500 ppm of α-tocopherol and subjected to the oxidation at 50°C for 9 days. The level of oxidation was determined by measuring peroxide value (PV), conjugated dienes (CD) and thiobarbituric acid reactive substances (TBARS). Chemometric analysis indicated that, under the conditions of the present study, PV was the most suitable indicator of oil oxidation. The results have shown that the α-tocopherol could have an anti- oxidant or pro-oxidant effects, depending on its concentration and initial level of oil oxidation. Results also show that α-tocopherol addition at all the concentrations tested resulted in pro-oxidation of the moderately oxidized oils;hence additional supplementation with α-tocopherol could not be recommended to delay oxidation of unrefined almond oil.

The Potential Application of <i>Syzygium aromaticum</i>and <i>Cymbopogon citratus</i>Essential Oils as Natural Preservatives of Beef Patties

The effect of essential oils from Syzygium aromaticum and Cymbopogon citratus on the lipid oxidation and microbial growth in beef patties was investigated in the present study. Essential oils were incorporated into the beef patties at 0.1% and 0.2% (w/w). The beef patties were then inoculated with cultures of E. coli and S. aureus and stored at 4°C. The control patties were processed without essential oil but inoculated with E. coli or S. aureus. The proximate composition, lipid oxidation and microbial counts were carried out after 7, 14, 21 and 28 days. Results showed that the incorporation of essential oils in beef patties did not significantly (P S. aromaticum at 0.2% reduced the E. coli growth by 1.48 log CFU/g and that of S. aureus by 6.52 log CFU/g while the incorporation of C. citratus at 0.2% reduced the E. coli growth by 1.21 log CFU/g and that of S. aureus by 1.4 log CFU/g after 28 days of storage. The pH measurement during the storage period showed a slight drop during the first 7 days of storage and an increase during the last 21 days in all samples. The sensory test of the beef patties showed that the consumers accepted patties formulated with the two essential oils. But the one made with 0.1% essential oil of S. aromaticum was the most accepted. The analysis of the color of beef patties between 0 and 28 days of storage revealed that the incorporation of essential oils retarded the degradation of the color of patties. Results obtained in the present study indicate the possibility of exploiting Syzygium aromaticum and Cymbopogon citratus essential oils to protect beef patties against lipid oxidation and microbial growth.

Oxidative degradation of sunflower oil blended with roasted sesame oil during heating at frying temperature

The efficacy of roasted sesame oil(SO)on the oxidation deterioration of sunflower oil(SFO)during heating was investigated.The concentrations of SO in the SFO were 0,10%,20%,and 30%by volume.The oxidation profile of oil samples was monitored by evaluating the generation of oxidation products and chemical alterations in the oils'composition during heating at frying temperature(180℃).The results showed that the oxidation parameters(free fatty acid,peroxide value,p-anisidine value,total oxidation status,thiobarbituric acid value,and color index)increased significantly in SFO compared to blends or SO during thermal treatment.During heating,the concentration of polyunsaturated fatty acids(PUFA)was reduced with increased level of saturated fatty acids;these results were observed more in SFO than those of SO or blend oils.However,the presence of SO in SFO reduced the decomposition of PUFA.In Fourier-transform infrared spectroscopy,the peak intensities were significantly altered in SFO compared to the blend oils during heating.Based on the most analytical data,it may be agreed that the heating at frying temperature led to the generation of relatively higher contents of oxidative products in SFO compared to blend oils,showing a lower degree of oxidation occurred in blends.The best frying performance for the SFO was achieved by using 30%SO extracted from the roasted sesame seed.This study showed the proper blending of high polyunsaturated oil with SO can produce oil blends with high nutritional values and enhanced stability for daily cooking and deep-frying applications.

Comparative Evaluation of the Thermal Aging of Solid Insulation in Mineral Oil and Methyl Ester of Palm Kernel Oil

The purpose of this work is to determine the impact of thermal aging on the dielectric and physicochemical properties of the oil/paper mixed insulation. We performed a comparative analysis of dielectric paper dipped in two cooling fluids: palm kernel oil methyl ester (MEPKO) and mineral oil (MO). Two types of dielectric paper were used: Thermally Upgraded Kraft paper (TUK) and Nomex-910 paper (NP-910). An accelerated aging test was realized at 110°C during a total of 96 hours. Samples of oil and paper were collected after 0, 48, 72 and 96 hours for analyses purposes. The analyses performed included the measurement of the Breakdown voltage (BDV) of the dielectric papers, the Total Acid Number (TAN) and the Decay Dissolved Products (DDP) of the liquid dielectrics. The BDV of NP-910 is greater than the BDV of TUK. Concerning the type of oil, the BDV of dielectric papers impregnated with MEPKO is greater than the BDV of similar papers impregnated with MO, indicating a better preservation of paper when dipped in methyl esters. The analyses of TAN and DDP revealed that Nomex-910 improves the oxidation stability of MO, but reduces the oxidation stability of MEPKO. These results prove that methyl esters can be used as a substitute to replace mineral oils in power transformers. Furthermore, they show that NP can be used mainly in areas of transformer where solid insulation is subjected to high thermal and electrical stress, and TUK other places where solid insulation is required. Such combination could assure money savings and a better preservation of the oil viscosity.