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The effects of the agitation conditions and headspace‐to‐emulsion volume ratio on lipid oxidation in emulsions can be considerable, but have not been systematically investigated yet. In the current paper, lipid oxidation was monitored in model oil‐in‐water (O/W) emulsions at pH 4.0 and 25°C in the presence of 200 μM iron sulfate. The formation of primary (conjugated dienes and hydroperoxides) and secondary (p‐anisidine value and TBARS) oxidation products confirmed that using rotating or shaking devices doubled the rate of oxidation product formation compared to a non‐agitated system, as a result of enhanced oxygen transfer. Furthermore, we found that a higher headspace‐to‐emulsion volume ratio at least doubled the rate of lipid oxidation due to a higher amount of oxygen available per mass of oil, which is in agreement with the kinetics of the reaction. This indicates that the variation in literature data on lipid oxidation in emulsions can be attributed to differences in mixing conditions and volume ratios. These factors are crucial and should be reported systematically along with the agitation conditions, and sampling method. This will enable a better comparison of literature information. [ABSTRACT FROM AUTHOR]

In this study, oxidatively stable minimal neutralized sunflower seed oils were produced using three chemicals (Ca(OH)2, MgO, and Na2SiO3) under previously determined optimal process conditions. Lipid oxidation rates at these optimum conditions were compared to the oils neutralized with NaOH (0.20%, 40°C, 15 min). It was concluded that the oils neutralized by NaOH had the shortest hydroperoxide and hexanal lag phases, thus were the least stable oils. Oils neutralized by Ca(OH)2, MgO, and Na2SiO3 had lower FFA and higher oxidative stability than oil neutralized by NaOH. The study focused on which weak alkaline has higher oxidation stability and minimum FFA content and maximum acceptable tocopherol content. The oil neutralized by Ca(OH)2 had the lowest FFA value and highest total phenolics and α‐tocopherol contents and it had better oxidative stability than oil neutralized by NaOH. It suggests that Ca(OH)2 could be more effective in producing a high quality oil. [ABSTRACT FROM AUTHOR]

High oleic palm oil (HOPO) with high oleic and palmitic acid contents is a new vegetable oil that needs to find further use in food applications, while hazelnut skin oil (HSO) with high oleic acid content is a by‐product of hazelnut oil production and have no commercial value. The aim of the study was to obtain new oil blends for new food formulations with high oxidative stability and low (or reasonable) saturated fatty acid content using HOPO and HSO. For this aim, they were blended in the proportions of 0 to 100% (wt/wt), and fatty acid and tocol compositions, induction period and storage stability of the blends were evaluated. Tocotrienols (560.94 mg/kg) constitute the majority of the tocol content of HOPO, while tocopherols (437.69 mg/kg) were the major tocols of HSO. HOPO has a higher saturated fatty acid composition and lower monounsaturated fatty acids content than HSO. In general, it was determined that increasing the HSO ratio in oil blends reduced their oxidative stabilities, which is most likely because HSO is richer in total unsaturated fatty acids (91.8%) than HOPO (68.4%). In addition, tocotrienols are known to be stronger antioxidants than tocopherols. Although HOPO is rich in γ‐tocotrienol, which has a strong antioxidant activity, it also has some disadvantages such as having a high price and containing significant levels of saturated fatty acids (mainly palmitic acid). The optimum blend ratio was then determined as 50% HOPO:50% HSO considering oxidative stability and fatty acid compositions. [ABSTRACT FROM AUTHOR]

The effects of linolenic acid (18∶3) concentration, combined with IBHQ addition, temperature, and storage time, on the flavor stability of soybean oils (SBO) were evaluated. A descriptive panel was trained to evaluate the overall oil quality and the intensity of individual flavors of SBO during 12 mon of storage under fluorescent light at both 21 and 32°C. Chernoff faces were used to achieve a simplified and integrated interpretation of the multivariate sensory data and to facilitate the interpretation of the vast amount of the data. In early storage, SBO with low 18∶3 (2.2% 18∶3, LLSBO) showed better flavor stability than did SBO with ultra-low 18∶3 (1.0% 18∶3, ULSBO). This trend disappeared during storage. During 10- to 12-mon storage, a painty flavor became predominant in all oils, which may have made it difficult for panelists to detect differences in treatment effect on flavor characteristics of SBO. During early storage, oils with TBHQ addition had poorer overall oil quality and stronger beany, painty, and fishy flavors than did oils without TBHQ addition. This trend disappeared as storage time progressed to 10 mon. Oils storedat 32°C had poorer overall oil quality and stronger painty, fishy, and beany flavors than did oils stored at 21°C starting from 2-mon storage. [ABSTRACT FROM AUTHOR]

Skin‐care products are known delivery systems of functional lipids that can enhance the natural defense of skin. Unsaturated lipids, e.g., linoleic acids, are more susceptible to lipid oxidation than saturated lipids. Therefore, lipid oxidation must be prevented to preserve the functionality of the unsaturated lipids in skin‐care products. The antioxidant properties of two Fucus vesiculosus extracts (water extract [WE] and 80% [v/v] ethanol extract [EE]) were evaluated. Both extracts had high in vitro antioxidant properties and a high phenolic content. The antioxidant efficacy of the extracts was evaluated by addition of 0.05% and 0.1% (w/w) freeze‐dried extracts to facial cream formulations. The cream was stored up to 42 days (dark, 20 °C) and the oxidative stability was determined by following tocopherol consumption and development in peroxides and secondary oxidation products. The results showed that EE was able to reduce the peroxide oxidation rate from 84.8% (control without extract) to 41.3%. Furthermore, a higher efficacy was observed for EE over WE. This was most likely related to higher phenolic content, high radical‐scavenging activity, and moderate metal‐chelating ability. However, WE indicated regeneration of tocopherols by amphiphilic polyphenolic phlorotannins, with interfacial properties. The results show that F. vesiculosus extracts rich in antioxidative phlorotannins can play an important role in reducing lipid oxidation and maintaining the quality of cream. [ABSTRACT FROM AUTHOR]

Essentially all fat-containing foods have the potential to undergo lipid oxidation even where unsaturated fatty acid compositions are low. Therefore, consumption of lipid oxidation products is potentially common with risk of consuming lipid oxidation products increasing in foods with high amounts of unsaturation (e.g. foods with omega-3 fatty acids), foods subjected to extensive thermal processing (e.g. fried foods), or food high in pro-oxidants (e.g. meats). Lipid oxidation generates potentially toxic products that have shown correlation with inflammatory diseases, as well as cancer, atherosclerosis, aging, etc. These potentially toxic products can enter the body through the diet and can develop in vivo during the digestion of lipids. Oxidation products can be absorbed into the blood and in some cases transported to tissues. The aim of this manuscript is to review how potentially toxic lipid oxidation products are formed and evaluate their potential to impact health. While lipid oxidation produces literally hundreds of oxidation products, this review focused on acrolein, 4-hydroxy- trans-nonenal, 4-hydroxy- trans-hexanal, crotonaldehyde, malondialdehyde, and cholesterol as they are the most reactive oxidation products and also the most studied. [ABSTRACT FROM AUTHOR]

The reliability of a method using H NMR analysis for assessment of oil oxidation at frying temperatures was examined. During heating and frying at 180 °C, changes of soybean oil signals in the H NMR spectrum including olefinic (5.16-5.30 ppm), bisallylic (2.70-2.88 ppm), and allylic (1.94-2.15 ppm) proton signals relative to glyceride backbone CH (5.30-5.46 ppm) and aliphatic CH (1.05-1.71 ppm) signals showed strong correlations with conventional analytical methods including total polar compounds, polymerized triacylglycerols, and changes of linoleic acid and linolenic acid peaks in gas chromatography. For oils rich in oleic acid, mid-oleic sunflower oil (NuSun) and high oleic soybean oil, only the olefinic and allylic proton signals are recommended for analysis due to the relatively low intensity of the bisallylic proton signal. Under these heating and frying conditions, signals indicating intermediate oxidation products, hydroperoxides, were not detected while very small signals corresponding to a variety of aldehydes including alkanal, branched alkenal, 2-alkenal, and aldehydes of conjugated dienes and epoxides were observed. In this study, it was found that the H NMR method is a fast, convenient, and reliable analytical method to determine the oxidation state of frying oil. [ABSTRACT FROM AUTHOR]

Lipid oxidation is one of the major causes of oil deterioration causing off-flavors and consumer rejection. Fast, easy, and dependable assays for predicting lipid oxidation rates in foods are important for shelf-life prediction. In this study, an electron paramagnetic resonance (EPR) spin-trapping technique with N- tert-butyl-α-phenylnitrone (PBN) was tested to determine the lag phase of lipid oxidation in stripped soybean oil (SSO), SSO with added α-tocopherol, and commercial soybean, canola and corn oils. EPR intensity of spin-trapped products from SSO correlated well with lipid hydroperoxides formation for samples stored at 37 and 55 °C respectively. When the antioxidant α-tocopherol was added, the EPR signal intensity of oil samples increased-indicating sample deterioration-after 50-65% of α-tocopherol was consumed. When using the EPR method with commercial soybean, canola or corn oil stored at 55 °C, there was a poor relationship between EPR intensity and lipid hydroperoxides lag phases. However, a linear correlation was found between EPR signal intensity and hexanal formation. For example, EPR signal intensity lag phases were 5, 13 and 27 days for soybean, canola and corn oils, respectively which was similar to the hexanal lag phases of 5, 13 and 25 days for the same oils. The EPR spin-trapping assay method has several advantages over headspace hexanal measurements, especially with regard to easier sample handling and shorter analysis times. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare three different collection methods; purge and trap, solid phase micro extraction and automated dynamic headspace/thermal desorption, all followed by GC-MS analysis used for the measurements of concentrations of volatile oxidation products in three different food matrices, namely oil, emulsion and milk. The linearity ranges of calibration curves obtained by the three different methods were compared for oil samples. Overall, the results showed that the three collection methods were comparable, although there were large differences in the linearity range of the calibration curves depending on the collection method. However, some challenges were observed for solid phase micro extraction and automated dynamic headspace/thermal desorption, namely, competition problems and overestimation of concentration by calibration curves, respectively. Based on the results, we suggest mainly to apply solid phase micro extraction on simple matrices and to be cautious with more complex matrices such as enriched milk and highly oxidized oils. Thereby, the study confirmed some challenges observed by other authors regarding competition problems on the fiber when using solid phase micro extraction. Furthermore, we observed that purge and trap, and automated dynamic headspace/thermal desorption were excellent for extraction of volatile compounds in all three matrices. However, automated dynamic headspace/thermal desorption calibration curves did provide an overestimation for oil samples so results must be interpreted with caution. [ABSTRACT FROM AUTHOR]

In recent years, H NMR has been used to study epoxides in lipid oxidation and industrial processes, but the peak assignments reported for monoepoxides and diepoxides have been inconsistent. Lack of clear assignments for chemical shifts of epoxides derived from polyunsaturated fatty acids (PUFA) has also limited the use of H NMR in detecting and quantifying these products during both oxidative degradation and industrial epoxidation. In this study, H NMR was used to characterize the epoxides synthesized from trilinolein, trilinolenin, canola oil, and fish oils by reaction with formic acid and hydrogen peroxide. Assignments for epoxides derived from PUFA in canola oil and fish oil were between 2.90-3.23 ppm and 2.90-3.28 ppm, distinct from other chemical groups in these oils. Chemical shifts of epoxy groups moved downfield with an increasing number of epoxy groups in the fatty acid chain. Hence, peaks for diepoxides appeared at 3.00, 3.09, and 3.14 ppm and for triepoxides at 3.00, 3.16, and 3.21 ppm. Results also suggested that stereoisomers of diepoxides and triepoxides were formed during the epoxidation process under the conditions of this study. These new assignments for di- and tri-epoxide stereoisomers were supported by GC-MS analysis of their methyl esters, H-H COSY experiments, and a re-evaluation of several previous epoxide-related studies. [ABSTRACT FROM AUTHOR]

This study investigated the influence of water content in combination with selected minor components including oleic acid, stigmasterol, α-tocopherol, and Trolox on their association colloid formation as well as their impact on lipid oxidation in bulk corn oil. First, surface activity of each minor component was evaluated by determining the ability of these components to lower the interfacial tension between bulk oil and water. All components but α-tocopherol were able to decrease interfacial tension of stripped oil. Second, the critical micelle concentration (CMC) of each minor component was determined in bulk oil with no water added and in the presence of 1000 ppm of water. In the bulk oil without extraneous water, we could not determine the CMC of minor components in the range of concentrations studied. However, in the presence of 1000 ppm of water, only stigmasterol could form association colloids at the CMC of 20 mmol/kg oil. Last, the effect of water content (400 and 1000 ppm) and minor components on lipid oxidation in bulk oil was studied by following the lipid hydroperoxides and hexanal formation during storage at 55 °C. Different water content did not significantly impact the lag time of lipid oxidation compared with the control. Interestingly, water caused prooxidant by decreasing the lag time of lipid hydroperoxides and hexanal formation in bulk oil containing oleic acid, stigmasterol, and Trolox compared with the control of each system. On the other hand, there was not significant impact of water on the antioxidant activity of α-tocopherol, a lipid soluble antioxidant in bulk oil. This study highlights the impact of water content on the surface activity of minor components as well as on the oxidative stability in bulk oil. [ABSTRACT FROM AUTHOR]

The toxic lipid peroxidation product, α,β,4-hydroxy-2- trans-nonenal (HNE) concentration, was measured in French fries (FF) from six local fast food restaurants. FF were purchased between 2 and 3 pm from all six restaurants. FF were also purchased at 12, 2, 4, 6 pm from one and at 1, 3, 5, 7 pm from another restaurant. Samples were analyzed for total fat, fatty acid distribution and for HNE by high performance liquid chromatography (HPLC). HNE was confirmed by HPLC/MS. HNE concentrations in FF from the 6 fast food restaurants were between 7.83 and 32.15 µg HNE/100 g FF and between 0.9 and 4.9 µg HNE/g extracted fat. HNE concentrations in FF purchased at 12, 2, 4, 6 pm were between 19.07 and 32.15 µg/g of FF and purchased at 1, 3, 5, 7 pm were between 7.47 and 10.21 µg HNE/100 g of FF. Differences in FA distribution were observed in the samples from some restaurants. FF which contained higher levels of linoleic acid (LA) also contained more HNE. It is clear that HNE is produced during the heating process of the frying oils and is incorporated into FF. Frequently consumed foods containing considerable amounts of HNE, a toxic aldehyde, may be a public health concern since HNE toxicity is related to a number of common pathological conditions. [ABSTRACT FROM AUTHOR]

Natural antioxidants to inhibit oxidation in edible oils are in high demand. Grape pomace is an abundant, inexpensive source of polyphenolic antioxidants, which are responsible for numerous health benefits. We examined pomace from eight varieties of Midwestern hybrid grapes for phenolic content and antioxidant activity. Ethanolic extracts produced from the pomace of each grape variety were added to two model systems, bulk soybean oil and oil-in-water emulsions, to determine antioxidant activity. Oxidation was monitored in each model system at a temperature appropriate to that particular system. While the extracts had relatively little effect in bulk oil, we observed dose-dependent antioxidant effects of some extracts in oil-in-water emulsions. Oxidation in bulk oils was assessed via total polar compounds and polymerized triacylglycerols. Oxidation in emulsions was assessed by peroxide value, headspace oxygen measurements, gas chromatography of headspace volatiles, and fatty acid analysis. Pomace extracts derived from red grapes generally outperformed those from white grapes, with the Marechal Foch variety showing high antioxidant activity at intermediate concentrations. At higher concentrations, Marechal Foch, Corot Noir, Frontenac, and Norton extracts showed promising antioxidant activity. This is the first report on antioxidant activity in an oil and emulsion setting for many of these grape varieties. [ABSTRACT FROM AUTHOR]

Effects of surfactant concentration, antioxidants with different polarities, and chelator type on the oxidative stability of water-in-stripped walnut oil (W/O) emulsions stabilized by polyglycerol polyricinoleate (PGPR) were evaluated. The formation of primary oxidation products (lipid hydroperoxides) and secondary oxidation products (hexanal) decreased with increasing PGPR concentrations (0.3-1.0 wt% of emulsions). Excess surfactant might solubilize lipid hydroperoxides out of the oil-water interface, resulting in the decreased lipid oxidation rates in W/O emulsions. At concentrations of 10-1000 μM, the polar Trolox demonstrated concentration-dependent antioxidant activity according to both hydroperoxide and hexanal formation. The antioxidant efficiency of the non-polar α-tocopherol was slightly reduced at the higher range of 500-1000 μM based on hydroperoxide formation. Both ethylenediaminetetraacetic acid (EDTA) and deferoxamine (DFO) at concentrations of 5-100 μM reduced the rates of lipid oxidation at varying degrees, indicating that endogenous transition metals may promote lipid oxidation in W/O emulsions. EDTA was a stronger inhibitor of lipid oxidation than DFO. These results suggest that the oxidative stability of W/O emulsions could be improved by the appropriate choice of surfactant concentration, antioxidants, and chelators. [ABSTRACT FROM AUTHOR]

Although fatty acid (FA) composition is known to be of fundamental importance to oxidative stability in lipids, consistent quantifications of the magnitude of this association have proved elusive. The objective of this study was to quantify the relationship between FA composition and stability on a large scale within comparable lipid systems, with the numerical effects of individual outcome factors (e.g. output of a singular assay, oxidative products after a brief period of time, etc.) attenuated by incorporation into a comprehensive summation of stability. The stability of 50 plant-based oils and fats was modeled according to FA composition, utilizing a quantification of stability that encompassed the complete oxidation curves of four distinct classical assays (two 1° and two 2° oxidation assessments) throughout 2 months of accelerated storage (60 °C). In our models, the concentrations of monounsaturated FA (MUFA), diunsaturated FA (DiUFA), and triunsaturated FA (TriUFA) together demonstrated a very strong correlation with our consolidated measure of stability ( r = 0.915; greater than observed with our assessments by individual assays). The resultant model also indicated the relative effect upon magnitude of oxidation of MUFA:DiUFA:TriUFA to be approximately 1:3:12-substantially greater than the 1:2:3 ratio of their relative unsaturation. [ABSTRACT FROM AUTHOR]

Fish oil is available primarily as triacylglycerols (TAG) or ethyl esters (EE). Anecdotal evidence suggests that TAG have superior bioavailability and oxidative stability compared to EE. In this work, peroxide value (PV) and p-anisidine value (AV) were used to monitor oxidation in commercially available TAG and EE fish oils incubated at temperatures from 5 to 60 °C. Pseudo first-order kinetics were assumed and rate constants were calculated for each temperature. At all temperatures, the rates of oxidation were higher for EE oils than TAG oils. For PV and AV measured in both oils, non-linear Arrhenius models were plotted, generating activation energies that ranged from 7 to 103 and 2 to 159 kJ/mol for PV and AV, respectively. Although TAG were more resistant to oxidation than EE, they had lower activation energies ( E) at ≤15 °C for reactions measured with PV and AV. The E for EE was negative at temperatures ≥45 °C, indicating that reaction rate was influenced by factors in addition to temperature. [ABSTRACT FROM AUTHOR]

Membraneless electrolyzed water (MLEW) is generated by electrolysis of dilute salt water solution without a membrane separating cathodic and anodic water. The stability of MLEW under different storage temperatures and pHs, as well as its lipid oxidizing effects have not been extensively studied. In this study, three storage temperatures and two pH conditions were used to study the stability of the water. MLEW's lipid degradation potential was investigated using two methods by measuring the degree of oxidation of lipids containing polyunsaturated fatty acids. Lipid oxidation in an emulsion model free of other interferences was conducted with MLEW containing 30, 50 and 100 mg L free chlorine (FC), and lipid oxidation in a salmon fish fillet was conducted by washing the fillet pieces with MLEW containing 100 mg L FC. We found that the MLEW was relatively stable in capped containers under both acidic and neutral pH during the 21-day period. Although there was significant lipid oxidation in the emulsion system, and the extent of oxidation was FC concentration dependent, we did not observe significantly more lipid oxidation in fish treated with MLEW compared to the control (stored under 4 °C for 10 days). Therefore, we conclude that MLEW may be used as a disinfectant in commercial operations without causing significant lipid oxidation and rancidity generation in foods. [ABSTRACT FROM AUTHOR]

Accelerated solvent extraction (ASE) was evaluated for extracting lipids from baked and extruded dry pet foods to determine factors controlling extraction efficiency and effects on lipid oxidation. Hydroperoxide decomposition and new lipid oxidation were minimal at 40 °C but increased at higher extraction temperatures without increasing yields. Maximum extraction required grinding samples to 250 µm particles, presence of polar solvents [chloroform, chloroform/methanol 2:1 (v/v) mixed, hexane/methanol 2:1 (v/v)], and a minimum of 20 min total static extraction time in repeat extraction cycles. Hexane and methanol injected into extraction cells simultaneously but separately was able to nearly duplicate extractions of chloroform/methanol, providing an option for replacing toxic chlorinated hydrocarbon solvents in ASE. However, lipid oxidation was higher in hexane. Yields were quantitative in baked biscuits but lower in extruded kibbles due to more dense, complex molecular structures. ASE extraction yields of 40 min or less were comparable to manual extraction yields of 24-48 h, with lower oxidation. Overall, one or two ASE extraction cycles with static times less than 20 min appeared to provide adequate lipid yields that accurately reflect lipid composition while inducing minimal modification when lipid oxidation products are the analytical endpoint. [ABSTRACT FROM AUTHOR]

Association colloids formed by surface active minor components play an important role in the oxidative stability of bulk oils. To imitate the formation of nanostructures in refined oils, multiple surface active minor components including phospholipids, free fatty acids, diacylglycerols and sterols were added to stripped corn oil. The critical micelle concentration (CMC) of the mixed components was determined. The impact of mixed minor components at below and above their CMC on oxidative stability of bulk oil and on antioxidant activity of α-tocopherol and Trolox was investigated. The CMC of the mixed surface active components in bulk oil was 20 µmol/kg oil in the presence of 383 ± 2 ppm of water. 1,2-Dioleoyl- sn-glycero-3-phosphocholine (DOPC) played an important role on the formation of association colloids since it was the most important component in forming the association colloids as confirmed by CMC and fluorescence probe studies. The association colloids formed by the mixed components showed prooxidative activity in bulk oil as determined by monitoring the formation of lipid hydroperoxide and hexanal. The activity of α-tocopherol or Trolox was not changed by mixed components association colloids. These results suggest that association colloids both physically and chemically impacted the oxidative stability and activity of antioxidants in bulk oil. [ABSTRACT FROM AUTHOR]

Phospholipids are important minor components in edible oil that play a role in lipid oxidation. Surface active phospholipids have an intermediate hydrophilic-lipophilic balance value, which allows them to form association colloids such as reverse micelles in bulk oil. These association colloids can influence lipid oxidation since they create lipid-water interfaces where prooxidants and antioxidants can interact with triacylglycerols. In this study, we examined the formation of reverse micelles in a stripped oil system by dioleoyl phosphoethanolamine (DOPE) and the effect of these physical structures on lipid oxidation kinetics. The critical micelle concentration (CMC) of DOPE was approximately 200 µmol/kg oil at 45 °C. Oxidation kinetics studies showed that DOPE was prooxidative when it was above its CMC (400 and 1,000 µM), reducing the lag phase from 14 days (control) to 8 days. The addition of combinations of DOPE and dioleoyl phosphocholine (DOPC) resulted in formation of mixed micelles with a CMC of 80 µmol/kg oil at 45 °C. These mixed micelles were also prooxidative when concentrations (100 and 500 µM) were above the CMC, decreasing the lag phase from 14 to 8 days. These findings provide a better understanding of the role of phospholipids in lipid oxidation of edible oil and could contribute to better antioxidant solutions. [ABSTRACT FROM AUTHOR]

There is an increasing demand for fish oil containing omega-3. By-products (e.g., heads, tails, belly flaps, backbones, and viscera) from fish fillet production are currently utilized for production of fish oil and fish meal for feed but can be a valuable source of omega-3 for human consumption. However, the quality of some oil is not good enough for human consumption due to oxidation during processing. The aim of this work was to decrease oxidation during oil production by adding antioxidants to herring by-products early in the production process. Of several antioxidants the most potent were selected by a fast screening test. Butylated hydroxytoluene, propyl gallate and citric acid were further evaluated on a labaroatory scale and pilot plant production of herring oil. The selected antioxidants resulted in lower total oxidation during processing [up to 71% reduction in TOTOX (2 times the peroxide value plus the anisidine value)]. In addition, higher oil stability was achieved by adding antioxidants during processing (improved stability up to 400%). [ABSTRACT FROM AUTHOR]

Flaxseeds have been recently in focus due to the antioxidant capacity of some of their compounds. However, there is a lack of easily accessible information concerning their activity against lipid oxidation in food systems. Therefore, the aim of the study was to determine the effect of defatted meals (DFM) and the aqueous extracts (AFE) obtained from brown and golden flaxseeds on lipid oxidation in pork meatballs. Fatty acid composition, peroxide value (PV), thiobarbituric acid reactive substances (TBARS) and cholesterol content were monitored during 6 months of freezer storage. Cholesterol oxidation products were identified and quantified. Both DFM and AFE limited fatty acid and cholesterol oxidation during meatball storage. Their antioxidant effect depended on flax variety (brown or golden) and preparation type (DFM or AFE). Lower level of PV and TBARS, compared with the ones with AFE, were noted in meatballs with DFM. Both DFM and AFE, from the brown seed variety, protect the lipids against oxidation to a higher extent. During the storage, a cholesterol degradation was observed. AFE (particularly from the brown variety) limited changes in cholesterol content. Moreover, they stabilized fatty acid composition of stored meatballs. However, DFM efficiently inhibited cholesterol oxidation. [ABSTRACT FROM AUTHOR]

Essential oils with antioxidant properties are of increasing interest in West Africa where there are many antioxidant rich plants. The objective of this study was to determine the essential oil extracted from six native plants ( Lippia multiflora, Lippia rugosa, Monodora tenuifolia, Ocimum gratissimum, Pimenta racemosa, Cymbopogon citratus) extracted by hydrodistillation from local plants in Benin. These samples were also evaluated for their antioxidant capacity using the conjugated autoxidizable triene (CAT) assay performed in stripped tung oil-in-water emulsion. The essential oil of P. racemosa, containing high amounts of chavicol (10.3 %) and eugenol (54.5 %), showed the strongest antioxidant activity, followed by that from O. gratissimum containing large amounts of thymol (50.2 %). The essential oil extracted from M. tenuifolia exhibited a moderate antioxidant activity. This essential oil is primarily composed of sesquiterpene alcohols such as α-cadinol (20.5 %), its isomer, α-muurolol (14.7 %), and germacrene D-4-ol (16.8 %). Essential oils from L. multiflora, L. rugosa and C. citratus oils showed poor ability to protect tung oil from oxidation. Finally, essential oils containing phenolic compounds and, in a lesser extent, sesquiterpene alcohols, exhibited the highest CAT values indicating that these compounds are the key determinants of the antioxidant activity of these essential oils in oil-in-water emulsions. [ABSTRACT FROM AUTHOR]

The effect of gamma irradiation on fatty acid composition and lipid oxidation in emulsion-type cooked beef sausages was investigated. Vacuum-packaged sausages were irradiated at 2, 4, 6 and 8 kGy and stored at 4 °C for 4 weeks. Samples were analyzed for fatty acid composition at 0 and 4 weeks and lipid oxidation after 0, 1, 2, 3 and 4 weeks of storage. Irradiation reduced the content of oleic acid and linoleic acid, and the effect was intensified during storage. Elaidic acid content increased at doses of 6 and 8 kGy. The results indicated that irradiation at 6 and 8 kGy increased lipid oxidation, measured as the thiobarbituric acid reactive substances value. Based on the results, cooked beef sausages could be irradiated at 2 and 4 kGy without affecting the molecular structure of lipids. [ABSTRACT FROM AUTHOR]

Association colloids such as phospholipid reverse micelles could increase the rate of lipid oxidation in bulk oils. In addition to phospholipids, other surface active minor components in commercial oils such as free fatty acids may impact lipid oxidation rates and the physical properties of reverse micelles. In this study, the effects of free fatty acids on changes in the critical micelle concentration (CMC) of 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) in stripped corn oil (SCO) were determined by using the 7,7,8,8-tetracyanoquinodimethane solubilization technique. Different free fatty acids including myristoleic, oleic, elaidic, linoleic and eicosenoic were added at 0.5 % by wt along with the DOPC into the bulk oils. There was no significant effect of free fatty acids with different chain length, configuration and number of double bonds on the CMC value for DOPC in bulk oil. However, increasing concentrations of oleic acid (0.5 to 5 % by wt) caused the CMC value for DOPC in bulk oils to increase from 400 to 1,000 μmol/kg oil. Physical properties of DOPC reverse micelles in the presence of free fatty acids in bulk oils were also investigated by the small angle X-ray scattering technique. Results showed that free fatty acids could impact on the reverse micelle structure of DOPC in bulk oils. Moreover, free fatty acid decreased pH inside reverse micelle as confirmed by the NMR studies. The oxidation studies done by monitoring the lipid hydroperoxide and hexanal formation revealed that free fatty acids exhibited pro-oxidative activity in the presence and absence of DOPC. Different types of free fatty acids had similar pro-oxidative activity in bulk oil. [ABSTRACT FROM AUTHOR]

Lipid oxidation is the major form of deterioration in foods because it decreases food quality and nutritional value, and may have negative health implications. Selected aromatic plant extracts from leaves, flowers and stems of rosemary, thyme and lavender were investigated for their antioxidant activity. The total polyphenol content was determined by the Folin-Ciocalteu assay and the antioxidant capacity was determined by the Trolox equivalent antioxidant capacity, 1,1-diphenyl-2-picrylhydrazyl, oxygen radical absorbance capacity and ferric-reducing antioxidant power assays. For all four antioxidant assays, the extracts from thyme flowers, lavender leaves and thyme leaves had the highest antioxidant activity, followed by rosemary stems, rosemary leaves, and lavender stems, and the lavender flowers and thyme stems had the lowest antioxidant activity. The antioxidant activity was correlated with the polyphenol content, although minor deviations were observed. In oil-in-water emulsion, extracts from rosemary leaves and thyme leaves were most effective at retarding oxidation followed by the rosemary stems and thyme flowers. Extracts from thyme flowers and lavender leaves were less effective in the emulsion than predicted by the homogeneous antioxidant assays. This study demonstrated the potential use of plants extract as substitutes for synthetic antioxidants. [ABSTRACT FROM AUTHOR]

β-Carotene is one of the most important fat soluble pigments with well-known antioxidant and pro-vitamin A activity. It is used in industries as a food colorant and a source of vitamin A. The thermal induced degradation during processing of wide varieties of carotenoid-rich foods leads to color and properties losses. The thermal stability of edible oils is thus of great importance to food manufacturers. Corn oil, rapeseed, and sunflower oils were fortified with 50-300 μg/g of β-carotene and oxidized using a Rancimat apparatus (air flow rate 20 L/h) at 110 °C for 14 h. β-Carotene degradation was measured using high performance thin layer chromatography and confirmed by HPLC-DAD-MS. Triacylglycerols and polar compounds (PC) were determined using LC-ESI-MS. Results showed that most of the β-carotene was degraded during the first 5 h of the thermal oxidation. It was found that the addition of β-carotene produces significant effects ( P < 0.05) on the peroxide index, free fatty acid values and radical scavenging activity of the three oils. Triacylglycerols containing high amounts of oleic acid show higher stability toward thermal oxidation and β-carotene treatment. Among the oils, rapeseed oil was the most stable oil in terms of the formation of polar compounds (PC), followed by corn oil, while sunflower oil was more prone to oxidation and thus higher amounts of PC were formed. [ABSTRACT FROM AUTHOR]

The present study presents the antioxidant activity of sesamin in canola oil compared with that of butylated hydroxytoluene (BHT) by monitoring the oxygen consumption and the decrease in linoleic acid and α-linolenic acid. The oxidation of canola oil was conducted at 35, 60, 90, 120 and 180 °C with addition of 50-400 ppm sesamin. Results from the oxygen consumption test showed that sesamin dose-dependently inhibited the oxidation of canola oil at concentrations of 50-200 ppm at temperatures of 60-180 °C, however, sesamin lost its antioxidant activity at a low temperature of 35 °C. The fatty acid analysis also demonstrated that sesamin at 50, 100 and 200 ppm dose-dependently prevented the oxidation of linoleic acid and α-linolenic acid in canola oil. Both the oxygen consumption and the fatty acid analysis demonstrated sesamin was less effective than BHT as an antioxidant at temperatures of 60-180 °C. It was therefore concluded that sesamin could prevent the lipid oxidation of frying fats and oil, however, its antioxidant activity was not as potent as that of BHT. [ABSTRACT FROM AUTHOR]

Effects of added phosphates on retardation of lipid oxidation of salted cod during processing, storage and after rehydration were investigated. Lipid hydrolysis progress and development of color, primary and secondary lipid oxidation products and fluorescence intensities were determined. Added phosphates significantly retarded lipid hydrolysis and lipid oxidation progress, resulting in lower free fatty acid , lipid hydroperoxides (PV), thiobarbituric acid-reactive substances (TBARS) as well as fluorescence intensities (δ F and δ F). Significant correlation between the lipid oxidation products (PV, TBARS, δ F and δ F) and yellow/brownish discoloration ( b* value) of salted cod was observed. Principal component analysis showed that TBARS, b* value and δ F were the strongest indicators of lipid oxidation during salting and storage. [ABSTRACT FROM AUTHOR]

Lipid oxidation products can arise when oils are subjected to high temperature and exposed to oxygen. Many of these oxidation products have higher polarity than the original triacylglycerols due to the incorporation of oxygen. These polar oxidation products could have a negative impact on oxidative stability by acting as prooxidants. In this study, the influence of polar lipid oxidation products on the oxidative stability of bulk oils and oil-in-water emulsions was investigated. Polar compounds were isolated from used frying oil by silica gel column chromatography. They were added to bulk stripped corn oil (with/without reverse micelles formed by dioleoylphosphatidylcholine, DOPC) and oil-in-water (O/W) emulsion to evaluate their prooxidative activity. Polar compounds increased lipid oxidation in bulk oil with and without DOPC. The presence of DOPC reverse micelles decreased the prooxidant activity of the polar oxidation products. On the other hand, there was no significant effect of the polar compounds on oxidation of O/W emulsions. To gain a better understanding of the polar compounds responsible for the prooxidant effect, linoleic acid and linoleic hydroperoxide were added into bulk oil at the same concentration as those in the polar fraction of the frying oil. However, they did not show the same prooxidative activity compared to oil with the polar fraction. [ABSTRACT FROM AUTHOR]

This study evaluated the effectiveness of grape seed extracts (GSE), green tea extracts (GTE), or butylated hydroxytoluene (BHT) on lipid oxidation reduction of potato chips stored for up to 90 days. The highest ( P ≤ 0.05) phenolic contents were detected in GSE (6134.5 mg gallic acid equivalent/100 g) followed by GTE and other plant extracts (oregano, thyme, terebinth, parsley, and bouncing bet). BHT had the greatest antioxidant activity (% inhibition) value (53.0) followed by GSE (42.6) and GTE (31.7). The GSE and GTE exhibited significantly higher antioxidant activities (measured by oxidative stability instrument) than the other plant extracts. The BHT and GSE at 1,000 ppm level was significantly the most effective in minimizing the peroxide value development during 90 days of storage. Descriptive results showed that higher levels of GSE and GTE (750 and 1,000 ppm) prevented the astringency development during 60 days of storage and minimized the off-notes, i.e., astringency and rancidity, during 90 days of storage. The cardboard attribute was not noticed when GSE and GTE, and BHT were added at 750 and 1,000 ppm levels. The GSE and GTE have a great potential for use as natural antioxidants to preserve the potato chips. [ABSTRACT FROM AUTHOR]

Lipid oxidation is a complex phenomenon involving free radicals which are highly reactive molecular species. The life-time of these radical species is extremely short and their detection is therefore difficult. Several electron spin resonance (ESR) spectroscopy methodologies make it possible to identify, quantify and measure the reactivity of radical species formed during oxidation-reduction reactions. In this study we took advantage of the specificity of ESR spectroscopy to detect radical compounds in order to determine the rate constants of hydroperoxide degradation, a key reaction involved in lipid oxidation. The interaction of 5-doxyl stearic acid and lipid-derived radicals was studied by following the intensity of ESR spectra. A kinetic model was developed to simulate data analysis obtained by ESR and values of rate constants for hydroperoxide degradation were determined at 100 and 110 °C. This quantitative approach of ESR spectroscopy has produced useful information about new rate estimates for hydroperoxide degradation in edible oils. [ABSTRACT FROM AUTHOR]

β-Carotene oxidation in the presence of both lipophilic α-tocopherol and hydrophilic ascorbic acid was experimentally studied in a biphasic oil-water system. Ascorbic acid in the water phase had two opposite effects of promoting and suppressing α-tocopherol consumption in the oil phase and indirectly participated in the antioxidation and prooxidation of β-carotene in the oil phase. The drastic antioxidation of β-carotene by stopping the consumption of α-tocopherol was caused by the depletion of oxygen in the system due to the oxidation of ascorbic acid. A kinetic model was constructed by incorporating the oxidation of ascorbic acid itself in the water phase, the regeneration and consumption of α-tocopherol by ascorbic acid at the oil-water interface, and the oxygen mass transfer across the gas-oil interface and the oil-water interface. The model well described the antioxidation and prooxidation behavior of β-carotene in the presence of α-tocopherol and ascorbic acid and the oxygen concentration profiles in each phase. The model was able to effectively determine the appropriate amounts of lipophilic and hydrophilic antioxidants to prevent β-carotene oxidation under various conditions. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the oxidative stability of conjugated linoleic acid rich soy oil (CLARSO) and the effects of conjugated linoleic acid (CLA) levels on volatile oxidation products formed during CLARSO oxidation. CLARSO oxidative stability was determined by gravimetric analysis, peroxide value, headspace oxygen analysis and p-anisidine value. Volatile oxidation compounds were analyzed by solid phase microextraction-gas chromatography with a flame ionization detector and a mass spectrometer. CLA oxidation results were highly dependent on analytical methods used and oxidation parameters measured. The gravimetric study showed a CLA concentration effect on oxidation, which was not seen in the headspace oxygen depletion and peroxide value. Volatile oxidation data indicate that CLARSO had significantly higher ( p < 0.05) levels of pentanal and trans-2-heptenal than the other oils, but there was no significant difference between the amounts of any volatiles present in 8 and 15% CLARSO. This suggests that oxidation was greater in CLARSO and that CLA concentration did not affect oxidation. [ABSTRACT FROM AUTHOR]

This study evaluated the effectiveness of grape seed extracts (GSE) on lipid oxidation of corn chips stored for 90 days in comparison to tert-butylhydroxytoluene (BHT). Proximate chemical analysis results showed that corn chips contained low moisture contents (less than 2%) and also that no significant differences were found in the dry matter values in ash, fat, protein, and fiber. Antioxidant activity of the GSE measured by an oxidative stability instrument ranged from 1.6 to 9.3 h of induction time, while BHT prevented oxidation by 18.8 h. GSE (800 ppm) increased the redness and decreased the brightness and yellowness of the corn chip samples, whereas no significant differences were observed for other concentrations of the GSE compared to the control. The peroxide values (PV) for the control and the lower concentration (200 ppm) of GSE increased from 4.5 to 32.7 mequiv/kg, and from 4.4 to18.7 mequiv/kg, respectively, while no increase in PV was found for the higher level (400 and 800 ppm) of GSE or BHT. These changes were observed after 90 days of storage. Descriptive and consumer results showed that the control and the low concentration of GSE were associated with an increase in rancidity and the appearance of off-flavor, while no noticeable increase in either rancidity or off-flavor was observed when using a higher concentration of GSE or BHT. GSE has great potential for use as a natural antioxidant to preserve the extruded corn chips. [ABSTRACT FROM AUTHOR]

This study was aimed at evaluating the effectiveness of phenolic antioxidants with a similar structure but having a different polarity in dried microencapsulated sunflower oil. The antioxidants tested were, on one hand, α-tocopherol and its water soluble analogue, Trolox, and on the other, gallic acid and its ester derivatives, propyl gallate and dodecyl gallate. At a moderate temperature (40 °C), the samples were oxidized under accelerated conditions by using Cu(II) as an oxidation catalyst. The progress of oxidation was followed up over time in the free and encapsulated oil fractions. The peroxide value, the total content of polymers and, when appropriate, the content of α-tocopherol were determined. Quantitative analysis of the total fraction of the non-volatile oxidation products and their distribution in oligomers, dimers and monomers was applied to samples to obtain a complete evaluation of oxidation. Finally, as a complementary measure, the antioxidants were also assessed by direct application of the Rancimat test at 100 °C on the dried microencapsulated oil samples. Results showed that the antioxidants of lower polarity in each series, i.e. tocopherol and dodecyl gallate, were to a great extent the most protective antioxidants. The results obtained by the Rancimat test were consistent with those found during oxidation at moderate temperature. Furthermore, the addition of Cu(II) reduced proportionally the oxidative stability index of the dried microencapsulated samples. [ABSTRACT FROM AUTHOR]

The aim of this work was to evaluate and compare the effects of conventional (hot air) and microwave drying on the lipid oxidation of stuffed pasta. Experiments were carried out on the pasta type ravioli dried by conventional and microwave treatments. Peroxide values and induction times were evaluated for the oil extracted from the stuffing. Peroxide values of the lipid extracts for the samples dried by conventional drying and microwave drying were similar (P-level = 0.51) and less than threshold acceptable value (25 mequiv O2/kg oil). The use of microwave processing could be a remarkable energy saving measure as well as a way of lowering production costs without compromising product quality. [ABSTRACT FROM AUTHOR]

The effect of emulsion structure on the susceptibility to oxidation of emulsified olive oils was tested. Olive oil samples were emulsified by adding a certain quantity of water in different ways. The resulting water-in-oil emulsions were then oxidized with UV light. The results revealed that the emulsion structure played a significant role in the oxidation process of emulsified olive oils. A kinetic mechanism is discussed based on the PV determined experimentally. The susceptibility of water emulsified extra virgin olive oils to oxidation was quantified by means of a dimensionless parameter that displayed a characteristic dependence on the specific surface area of the water dispersed phase. [ABSTRACT FROM AUTHOR]

Lipid oxidation is a major factor affecting flavor quality and shelf life of vegetable oils. Oxidative stability is therefore an important criterion by which oils are judged for usefulness in various food applications. In this study a method based on headspace analysis was developed to evaluate relative oxidative stability of canola oils. The method does not require the use of chemicals, involves minimal sample preparation, and can be performed on a relatively small sample size in comparison with traditional wet chemical methods. Canola oils freshly extracted in the laboratory from different seed samples were subjected to accelerated oxidation and analyzed for PV by standard methods and headspace volatiles by solid phase microextraction/GC-MS. Forward stepwise regression analysis of the data revealed a relationship between PV and headspace concentration of the volatile lipid oxidation products hexanal and trans, trans-2,4-heptadienal. The PV calculated using this formula correlated (R² = 0.73) with those measured by conventional methods. [ABSTRACT FROM AUTHOR]

Lipid oxidation includes a complex set of chemical reactions; and no single analytical method is available to give a satisfactory description of lipid oxidation status. High-resolution NMR spectroscopy techniques were tested to establish possible correlations with traditional analytical methods and to study lipid oxidation products. Ethyl esters of all-cis 4, 7,10,13,16,19-docosahexaenoic acid (DHA) (22:6n-3), with and without added α-tocopherol, were oxidized in the dark at 25°C in an air-circulating oven. Correlations were found between primary oxidation products (PV and conjugated dienes) and the appearance of peaks in the 8.0-10.5 ppm chemical shift region of the 1H NMR spectra. Multivariate data analysis (partial least squares; principal component regression) and the study of specific regions of the spectra obtained made it possible to easily separate samples of esters with and without α-tocopherol based on the oxidation products formed. Based on knowledge about lipid oxidation products formed in marine lipids, selected oxidation products have been studied in the 1H NMR spectra with the aim of finding detection limits and their chemical shift values. [ABSTRACT FROM AUTHOR]

This study determined the lipid content and FA composition of muscle and a mixture of muscle and viscera from Korean catfish as well as lipid oxidation and hydrolysis. Lipid content and FA compositions in Korean catfish, which were purchased every month or two during September 1999-July 2000, were analyzed. Lipid oxidation and hydrolysis were determined as PV, thiobarbituric acid value, and FFA in the muscle and the mixture during storage at 2°C for 12 d and -14°C for 9 wk. Lipid contents of the muscle and the mixture were 3.2 (w/w) and 5.4%, respectively. Oleic acid was the most abundant FA in the catfish lipids, constituting 28.0% (w/w) of total FA in the muscle and 25.6% in the mixture, followed by palmitic acid and linoleic acid, amounting to 20.2 and 12.2%, respectively, in the muscle and 20.2 and 12.5% in the mixture. EPA and DHA were 3.2 and 6.8%, respectively, in the muscle and 3.5 and 8.1% in the mixture. Seasonal variation in lipid contents and FA composition was minimal in catfish. Lipids in minced catfish oxidized and hydrolyzed readily at 2°C. Inclusion of viscera into the muscle increased lipid oxidation and hydrolysis. Frozen storage at -14°C and addition of ascorbic acid both reduced lipid oxidation. Frozen storage retarded lipid hydrolysis in catfish. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the relative rate of FFA formation and lipid oxidation of unseparated (head and broken), head, and broken rice and the effect of water washing on the lipid quality of broken rice. A regression model was developed with surface FFA or conjugated diene (CD) content vs. incubation time to determine the rates of FFA formation and lipid oxidation. The surface lipid contents of unseparated, head, and broken rice were 0.40, 0.38, and 0.50% of rice, respectively. FFA formation during storage showed three phases: an initial rapid formation, followed by a period of very little or no formation, and finally a phase of gradual formation. In contrast, CD formation initially showed a slow increase but later increased gradually with storage time. The relative rates of FFA and CD formation of unseparated, head, and broken rice were 0.0028, 0.0027, and 0.0036 and 0.192, 0.188, and 0.377, respectively. Water washing reduced the rates of FFA formation and lipid oxidation of broken rice to 0.0015 and 0.2192 from initial values of 0.0031 and 0.369, respectively. Water washing appears to be a simple and practical means of lowering the rates of FFA formation and lipid oxidation in broken rice. [ABSTRACT FROM AUTHOR]

An automated flow injection chemiluminescence (FICL) system for measuring lipid hydroperoxide (LOOH) concentrations in oils was developed. Initially, a crude oil-in-water emulsion (formed by mixing solvent-diluted oil with the aqueous-based CL compound, luminol, and the catalyst for the reaction, cytochrome c) was tested. The assay was rapid (60 samples per hour), reproducible (CV no greater than 10%, n=3) and had a low sample requirement (1 mg of oil) because of its high sensitivity (0.5 nmol LOOH). CL intensity was influenced by the amount and type of oil under analysis. Owing to these factors, quantitative data were attainable only with a uniform oil concentration and with a calibrant derived from an oil equivalent to that under analysis. This method yielded quantitative data in good agreement with an iodometric titration assay for LOOH ( r=0.9204). A refinement of the first method consisted of replacing the luminol and cytochrome c CL compounds with lucigenin, resulting in an assay insensitive to α-tocopherol. A monophasic reaction solution was devised to remove the effect of turbidity; however, the CL signal was still influenced by oil type. Therefore, quantitative data were still attainable only when the same type of oil was used for calibration. [ABSTRACT FROM AUTHOR]

The usefulness of the Oil Stability Index (OSI) as an accelerated oxidative stability test for canola oil was studied by correlating the OSI with the induction period as determined by sensory analysis. Canola oil was treated by holding it for differing times (0, 1, 2, 3, 4, and 6 d) at elevated temperature (60°C) in the dark with agitation. The sensory induction period (SIP) was determined by storing the five treatments of oil and the control at 60°C in the dark with agitation and removing aliquots of oil for a nine-member sensory panel to evaluate over a 9-d period. The time it took for a treatment to reach an average sensory score of 5 (10-point scoring scale) was defined as the treatment’s SIP. OSI values were obtained on day 0 using a heating block temperature of 110°C and an air pressure of 6 psi. The relationship between SIP and OSI had a 0.89 coefficient of determination ( r 2). This relationship may be sufficiently strong to warrant use of the OSI in industry applications but may not be ideal for more precise experimental studies of canola oil shelf life. [ABSTRACT FROM AUTHOR]

The objective of this study was to measure and compare differences in oxidized products of oil extracted from unoxidized and oxidized walnuts using five different extraction methods: (i) mechanical pressing, or solvent extraction with (ii) hexane, (iii) methylene chloride, (iv) chloroform/methanol, or (v) supercritical carbon dioxide (SC−CO2). Of the extraction methods evaluated, only chloroform/methanol and methylene chloride provided reasonable results for all parameters measured (total lipid yield, FA profile, PV, conjugated dienes, FFA content, and volatile content); however, chloroform/methanol extracted significantly greater levels of volatile compounds. The SC−CO2 extraction with purified gas was simple and accurate for all data except collection of volatile compounds, as these materials are lost during the lipid extraction. Pressing was neither quantitative nor qualitative, and hexane extraction retrieved significantly lower levels of volatiles than the other methods, except for SC−CO2. [ABSTRACT FROM AUTHOR]

A very sensitive high-performance liquid chromatography (HPLC) method was developed for the simultaneous separation and measurement of nonpolar and polar lipophilic secondary lipid peroxidation products in vegetable oil. Seventeen nonpolar and 13 polar lipophilic aldehydes and related carbonyl compounds, derived from thermally oxidized soybean oil as 2,4-dinitrophenyl hydrazones, were separated simultaneously by reversed-phase HPLC. Detection limit for the individual compounds is 1 ng. Thirteen of the nonpolar carbonyl compounds were identified as: butanal, 2-butanone, pentanal, 2-pentanone, hexenal, hexanal, 2,4-heptadienal, 2-heptenal, octanal, 2-nonenal, 2,4-decadienal, decanal, and undecanal. Three of the polar carbonyl compounds were identified as: 4-hydroxy-2-hexenal, 4-hydroxy-2-octenal, and 4-hydroxy-2-nonenal. The detection of the toxic 4-hydroxy-2-nonenal, a major compound, and 4-hydroxy-2-hexenal, a minor compound, in heated soybean oil is of particular importance because these toxic compounds have been shown to be absorbed from the diet. [ABSTRACT FROM AUTHOR]

A rapid and sensitive ultraviolet-visible spectrophotometric method for determination of peroxide value (PV) in foods with high carotenoid content (e.g., paprika oleoresin, paprika powder, red palm oil) has been developed. The proposed protocol [modified International Dairy Federation (IDF) method] was established from the IDF Fe(II)-oxidation-based spectrophotometric method, and the main one of the introduced modifications consisted of a clean-up extraction step of pigments before determining the PV by complexing Fe(III) ions with thiocyanate. Fe(II) oxidation time, reaction medium, and Fe(III)-thiocyanate complex formation time were optimized. The modified IDF method was compared with and was validated by iodometric AOAC official method with a good correlation ( R 2=0.957) between data obtained by both analytical methods. The high sensitivity of the method allows the use of only about 0.010–0.015 g of sample, with a detection limit of 0.044 mequiv peroxide/kg of sample. Therefore, an improved spectrophotometric method for assessing PV in food lipids with high carotenoid content is now available and can be applied to any kind of sample, independent of oil and pigment content. [ABSTRACT FROM AUTHOR]

The metal binding ability of Maillard reaction products (MRP) was investigated by spectrophotometric monitoring for complex/chelate formation. In addition, the antioxidant activity of MRP, in the presence of Cu(II), was evaluated on a lipid model system consisting of sunflower seed oil/water (1∶2). Results from the Rancimat test indicated a significant decrease in pro-oxidant ability of Cu(II) in the presence of MRP in contrast to histidine alone, whether heated or not. Results from the diphenylpicrylhydrazyl method showed that, in contrast to histidine (heated or not), the antiradical ability of MRP is reduced in the presence of Cu(II), but depends on the reaction time between MRP and Cu(II). [ABSTRACT FROM AUTHOR]

Validity of the oil stability index (OSI) as an accelerated test of oxidative stability has been questioned because of its high holding temperature, 110°C, which may cause reactions that would not occur at lower temperatures. The purpose of this study was to characterize the usefulness of OSI as an accelerated oxidative stability test for oil of varying metal catalyst content by correlating OSI with the sensory induction period of light-exposed soybean oil. Five 400-g aliquots of soybean oil were placed in Erlenmeyer flasks and treated with increasing levels of a metal pro-oxidant, Cu2+ 2-ethylhexanoate. Pro-oxidant concentration ranged from 0 to 3.13×10−5 M. Five-gram aliquots were taken from duplicate flasks and immediately tested using the Oxidative Stability Instrument. Heating block temperature was 110°C. Sample flasks were then exposed to 800 footcandles of light and held at ambient temperature for 3 wk. One-gram aliquots were regularly withdrawn and evaluated for rancidity by 10 trained panelists to determine the sensory induction period of each sample. Aliquots were also taken to determine OSI of light-exposed oil samples. Sensory induction periods were correlated with OSI, resulting in a squared partial correlation coefficient ( r 2) of 0.920. The r 2 for OSI of light-exposed oil samples ranged from 0.897 to 0.979. OSI appears to be an acceptable accelerated method for measuring the oxidative stability of light-exposed soybean oil that varies in metal catalyst content. [ABSTRACT FROM AUTHOR]

Nonvolatile triacylglyceride (TAG) oxidation products play an important role in the oxidative degradation of lipids. They serve as a reservoir of oxygen-containing species and hence can act as off-flavor precursors or as initiators for further oxidation reactions. Possible nonvolatile lipid oxidation products are TAG with a hydroperoxy, hydroxy, epoxy, or oxo (ketone or aldehyde) group or combination of these groups. The breakdown of TAG hydroperoxides yields nonvolatile glyceride species with two intact fatty acid chains and one short chain mostly ending in an aldehyde or hydroxy group (2 1/2 glycerides). By means of normal-phase high-performance liquid chromatography (HPLC) with mass spectrometric (MS) detection, non-volatile lipid oxidation products can be separated according to polarity. This results in separation into classes of TAG oxidation products, such as epoxy-TAG, oxo-TAG, hydroperoxy-TAG, hydroxy-TAG and 2 1/2 glycerides, which can be identified using selected ion chromatograms. The retention times of TAG oxidation products on the normal-phase HPLC system and the signal intensity of the MS detector are stable enough to enable quantitative analysis based on external calibration. The normal-phase HPLC-MS method is very suitable for the characterization and quantitation of nonvolatile TAG oxidation products in oxidized TAG reference compounds as well as in real oils or oil phases isolated from emulsions, spreads, or other fat-based food products. This method can give detailed information for the study of lipid oxidation mechanisms. [ABSTRACT FROM AUTHOR]