Bene hull oil as a highly stable and antioxidative vegetable oil

Fatty acid composition, peroxide value, acid value, iodine value, saponification number, unsaponifiable matter content, total tocopherols and phenolics contents, and wax content of Bene hull oil (BHO) were determined and compared to those of Bene kernel oil (BKO) and extra‐virgin olive oil (EVOLO). Considering the fatty acid composition and total tocopherols and phenolics contents, the resistance to the production of conjugated diene hydroperoxides and carbonyl compounds during the heating process at 170 °C for BHO was about 4.2 and 7.3 times and about 1.7 and 2.0 times those of BKO and EVOLO, respectively. The antioxidant activity of BHO was exactly the same as that of tert‐butylhydroquinone at low concentrations (100 ppm).     

Effect of Bene Kernel Oil on the Frying Stability of Canola Oil

Canola oil (CAO) with (0.05–0.4%) and without added bene kernel oil (BKO) and tert-butylhydroquinone (TBHQ, 100 ppm) was used for deep-fat frying of potatoes at 180 °C for 48 h. Frying stability of the oil samples during the frying process was measured based on the variations of total polar compounds (TPC) content, conjugated diene value (CDV), acid value (AV), carbonyl value (CV) and total tocopherols (TT). In general, frying stability of the CAO significantly (P < 0.05) improved in the presence of the TBHQ and BKO. The best frying performance for the CAO was obtained by using of 100 ppm TBHQ and 0.1% BKO. The effectiveness of TBHQ and BKO at these levels was found to be nearly the same. Increasing the level of BKO from 0.1 to 0.4% caused a decrease in the oxidative stability of the CAO, indicating the pro-oxidant effect of the oils added at these levels.     

Frying performance of the hull oil unsaponifiable matter of Pistacia atlantica subsp. mutica

The anti‐rancidity effect of the hull oil unsaponifiable matter (USM, 100 ppm) of Pistacia atlantica subsp. mutica (Bene) on sunflower oil (SFO) during frying at 180 °C was investigated and compared to that of tert‐butylhydroquinone (TBHQ, 100 ppm). The unsaponifiable constituents of the Bene hull oil (BHO) were separated into hydrocarbons (3.7%), carotenes (3.6%), tocopherols and tocotrienols (24.7%), linear and triterpenic alcohols (0.9%), methylsterols (5.7%), sterols (3.2%), triterpenic dialcohols (4.7%), and triterpenic dialcohol methylesters (4.5%), by means of silica gel TLC. The results obtained from the measurements of total polar compounds, conjugated diene value, carbonyl value, and acid value during 32 h of frying showed that the frying stability of SFO improves more in the presence of the USM of BHO than in the presence of TBHQ. Moreover, compared to TBHQ, the USM had a better protective effect on the indigenous tocopherols of SFO during frying.     

Comparison of methods for determining peroxidation in processed whole peanut products

Oxidation of fatty acids in peanut butter produces peroxides and changes in the conjugated diene contents. Two of the most widely used methods for measuring these oxidative effects, peroxide value and the spectrophotometric assay of conjugated diene hydroperoxides, were compared in determinations of shelf-life stability of peanut butters during short and long term storage. Results by the conjugated diene hydroperoxides method correlated with those by the peroxide value method over 4 and 12 week storage periods. The conjugated diene hydroperoxides method requires smaller samples and is quicker, more accurate, and simpler than the peroxide value method, nor does it require additional reagents nor depend upon a chemical reaction or color development.     

Influence of ascorbic acid and ascorbyl palmitate on the aroma composition of an oxidized vegetable oil and its emulsion

The formation of conjugated diene hydroperoxides and hexanal was compared to the development of aroma profiles during initial lipid oxidation of a vegetable oil and its 40% oil-in-water emulsion at 60°C. The aroma profiles of the oil and the emulsion with and without addition of ascorbic acid or ascorbyl palmitate were compared. The aroma compounds were isolated under a model mouth system and analyzed by gas chromatography/sniffing port analysis. Detectable odors were found and corresponded to 11 and 14 volatile compounds in the oil and the emulsion, respectively. The emulsion had higher lipid oxidation rates than the oil. Addition of ascorbic acid and ascorbyl palmitate had little influence on the aroma composition of the oil. In the emulsion, addition of these compounds resulted in diminished generation of odor active compounds. Results of measurements of conjugated diene hydroperoxides and headspace hexanal corresponded to that of the lipid oxidation rate in general, but predicted insufficiently the alterations in the aroma compositions by antioxidants.     

Frying stability of canola oil in presence of pumpkin seed and olive oils

Frying performance of canola oil (CO) was investigated in the presence of 5, 10, and 15% levels of virgin olive oil (VOO) and pumpkin seed oil (PSO) during frying of potatoes at 180°C. Acid value, carbonyl value, total polar compounds content, and total tocopherols content of the oil samples were determined during the frying process. VOO and PSO addition improved the frying stability of the CO. Frying performance of the CO increased more in the presence of PSO than in the presence of the VOO. The PSO levels higher than 5% exerted pro‐oxidant effects, indicating the necessity of investigation at lower levels. The better antioxidative effect of PSO was attributed to its probably different phenolic composition.     

Effect of ascorbyl palmitate on the quality of frying fats for deep frying operations

The addition of 0.02% ascorbyl palmitate (AP) reduced color development of frying fat (animal fat/vegetable oil [A-V] shortening) and vegetable oil (partially hydrogenated soybean [V-S] oil) in simulation studies. It also reduced peroxide values, development of conjugated diene hydroperoxides (CDHP) and their subsequent degradation to volatile compounds, such as decanal and 2,-4 decadienal, indicating that AP has the ability to inhibit thermal oxidation/degradation of frying fats and oils. A commercial french fry fat had lower CDHP values compared to A-V fat in simulated studies, and fried chicken oil had lower CDHP values than the V-S oil. Peanut oil had higher thermal stability than the other fats and oils.     

Analysis of autoxidized fats by gas chromatography-mass spectrometry: III. Methyl linolenate

The gas chromatography-mass spectrometry (GC-MS) method developed in the preceding papers was extended to the analysis of autoxidation products of methyl linolenate. Four isomeric hydroxy allylic trienes with a conjugated diene system were identified after reduction of the linolenate hydroperoxides. All eight geometrictrans,cis- andtrans, trans-conjugated diene isomers of these hydroxy allylic compounds were identified and partially separated by GC of the trimethylsilyl (TMS) ether derivatives. The proportion found of 9- and 16-hydroperoxides was significantly higher (75–81%) than the 12- and 13-hydroperoxides (18–25%). The tendency of the 12- and 13-hydroperoxides to form cyclic peroxides, cyclic peroxidehydroperoxides, and prostaglandin-like endoperoxides was supported by indirect evidence for the presence of 9,10,12- and 13,15,16-trihydroxyoctadecanoate in hydrogenated derivatives of the highly oxygenated products. The quantitative GC-MS method was used to determine the relative contribution of linolenate, linoleate, and oleate in mixtures to the formation of hydroperoxides. Presented at the AOCS Meeting, New York, May 1977.     

Concurrent oxidation of accumulated hydroperoxides in the autoxidation of methyl linoleate

Summary 1. Kinetic studies showed that concurrent oxidation of preformed hydroperoxides may be expected to take place at all stages of the autoxidation of methyl linoleate. The rate of oxidation relative to the rate of autoxidation of unoxidized ester is determined chiefly by the extent of the accumulation of hydroperoxides. 2. Infrared spectral analysis of hydroperoxides oxidized to various degrees indicated thattrans, trans diene conjugation and isolatedtrans double bonds produced in the autoxidation of methyl linoleate are related to the concurrent oxidation of the accumulated hydroperoxides. 3. The low absorptivity observed for diene conjugation, compared to that which may be expected for the exclusive production ofcis, trans diene conjugated hydroperoxide isomers during the autoxidation of methyl linoleate is attributed to the concurrent oxidation of accumulated hydroperoxides. 4. The effect of antioxidants in giving a well-defined induction period in the oxidation of hydroperoxides isolated from autoxidized methyl linoleate indicated that the oxidation proceeds by a chain reaction. 5. The primary reaction products of the oxidation of hydroperoxides isolated from autoxidized methyl linoleate were found to be polymers formed in a sequence of reaction involving the diene conjugation. 6. Studies on the autoxidation of methylcis-9,trans-11-linoleate showed thatcis, trans isomerization of the conjugated diene took place with the concurrent production of isolatedtrans double bonds and loss of diene conjugation. Hormel Institute publication no. 138. Presented before the American Oil Chemists’ Society, Philadelphia, Pa., Oct. 10–12, 1955. This work was supported by a grant from the Hormel Foundation.     

Improving the Frying Performance and Oxidative Stability of Refined Soybean Oil by Tocotrienol‐Rich Unsaponifiable Matters of Kolkhoung (Pistacia khinjuk) Hull Oil

Increasing consumer awareness for all natural products has quickly led to growing research on new resources of potent and profitable natural antioxidants. In this context, for the first time, the Kolkhoung hull oil (KHO) (Pistacia khinjuk)‐unsaponifiable matters (USM) (UHO) (100, 200, and 400 mg kg^?1) were incorporated into refined soybean oil (RSO) and the oxidative stability of prepared oils was measured during 32 hours of frying. Then, the obtained results (oxidative stability) were compared to the samples containing tert‐butyl hydroquinone (TBHQ) (100 mg kg^?1) as a common synthetic antioxidant. According to the results of oxidative stability assays of acid values, conjugated diene values and carbonyl values, and total polar compounds, the incorporation of UHO, particularly at a concentration of 200 mg kg^?1, was more efficient in improving the oxidative stability compared to TBHQ. The tocol content of KHO (2043.4 mg kg^?1) was higher than the reported amounts of other conventional edible oils. Furthermore, by incorporation of UHO into RSO, as compared with TBHQ, a better protection of naturally occurring antioxidants (tocopherols and sterols) was found after adding UHO to RSO. This fact was mainly attributed to the UHO's tocotrienol fraction. Hence, the USM of KHO can be used as a potent antioxidant to improve the oxidative stability of frying oils.     

Conjugated dienes and trienes from methyl oleate and methyl linoleate

Methyl oleate and methyl linoleate were converted to conjugated dienes and trienes, respectively, by selecting and modifying the conventional procedures usually applied to the generation and characterization of fatty hydroperoxides. Conditions have been studied in the laboratory for: (a) the optimum production of hydroperoxides with a minimum of by-products, (b) the effective separation and concentration of the resulting hydroperoxide, (c) the economic reduction of the hydroperoxide mixture, (d) simple dehydration of the reduced product, and, (e) recovery of the resulting polyene-rich material. If the processing sequence is halted after the reduction step, the resulting product,is a mixture of allylic hydroxy monoene or diene methyl esters. Our investigations have been extended to include studies on the methyl esters of commercial oleic acid and the mixture of methyl esters resulting from alcoholysis of lard oil. Products containing 20–25% conjugated diene and lesser proportions of conjugated triene were obtained. Presented at the AOCS Meeting, Houston, April 1965. E. Utiliz, Res. Dev. Div., ARS, USDA.     

Effect of membrane filtration on the flavor of virgin olive oil

Cross‐flow microfiltration (MF) and ultrafiltration (UF) with different commercial membranes were applied to virgin olive oil (VOO) in order to remove some compounds that are responsible for oil unpleasant flavor without altering the oil composition. Experimental tests were carried out using a Spanish VOO from Andalusia, which had the typical eucalyptus aroma. Several classical analytical parameters (acidity, peroxide number, UV absorbance) were determined. Moreover, the contents of total chlorophyll and minor polar compounds were detected. The effect of filtration on oil aroma was evaluated by detecting carbonyl compounds and by a panel of trained tasters. The UF Carbosep M1 membrane was the most suitable for softening the oil organoleptic features. Carbosep UF M1 and MF M14 membranes also induced a reduction of the content of total chlorophyll, which certainly slowed down the oil oxidation processes. It should be considered, however, that the observed decrease in the content of phenolic compounds with Carbosep M1 might have an adverse affect on the oil's stability to oxidation, but the observed decrease in total chlorophyll content should oppose it.     

Antioxidant activity of sesame,rice bran and bene hull oils and their unsaponifiable matters

Chemical composition of sesame (SEO), rice bran (RBO) and bene hull (BHO) oils was determined. During oven test, peroxide value on day 8 (PV₈, meq/kg) and carbonyl value on day 6 (CV₆, µmol/g) were considered as measures of resistance to the formation of primary and secondary oxidation products, respectively. The SEO and BHO showed statistically the same PV₈ (381.4 and 359.8, respectively) and CV₆ (25.2 and 25.8, respectively), and their stabilizing effect was significantly better than that of the RBO (455.5 and 32.7, respectively). The unsaponifiable matters (USM) fraction of the BHO (443.7 and 26.8, respectively) had an antioxidative effect higher than those of the SEO (478.0 and 38.6, respectively) and RBO (482.4 and 37.4, respectively). There was a good correlation (R² = 0.972) between the PV₈ and CV₆ throughout oxidation period. On the basis of the oxidative stability index (OSI, h) of Rancimat test, the best carry‐through properties belonged to the SEO (6.92 h), followed by the RBO (6.12 h) and BHO (5.0 h), and also a similar order was observed for the USM fractions (5.89, 5.28 and 4.50 h, respectively). There was no correlation between the results of Rancimat and oven tests, showing that the powerful antioxidative agents under oven test conditions were lack of appropriate carry‐through properties. The highest significant reducing power (mmol/L) belonged to the SEO (258.1), followed by the RBO (218.7) and BHO (152.4), whereas the USM fraction of the SEO indicated the least significant quantity among the USM fractions (89.3 vs. 216.6 and 158.0 for the RBO and BHO, respectively).     

Contribution of Compositional Parameters to the Oxidative Stability of Olive and Walnut Oil Blends

Oil blending was conducted to study the effects of changes in fatty acid composition (FAC), tocopherols and total phenol content (TPC) on oxidative stability of virgin olive oil (VOO):walnut oil (WO) blends. The measurement of the antioxidant activity of bioactive components present in the parent oils and blends was achieved by their ability to scavenge the free stable 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·). The highest percentage of DPPH· inhibition was found for pure VOO, and the lowest one for pure WO. EC₅₀ values obtained from the DPPH assay correlated significantly and inversely with TPC. The generation of volatile flavor components in VOO indicated the predominance of C₆ compounds produced through biochemical (enzymatic) pathways, whereas WO showed increased concentrations of medium chain (C₇–C₁₁) aldehydes produced through chemical (oxidative) pathways. The results obtained confirm the importance of VOO phenolics in providing protection against oxidation in VOO and VOO/WO blends. However, considering the impact of FAC and the content of endogenous antioxidant substances mentioned previously on the oxidative stability of the oils analyzed, the effect of an elevated unsaturation level (WO) prevails over a high amount of such bioactive components (VOO).     

Evaluation of antioxidant capacity of sesamol and free radical scavengers at different heating temperatures

Sesamol is a natural antioxidant found in sesame oil from roasted sesame seeds. Activation energy and antioxidant capacity of sesamol were determined and compared with other free radical scavengers (FRSs) including tert‐butylated‐hydroxyquinone (TBHQ), butylated‐hydroxyanisol (BHA), or α‐tocopherol in a lard model system treated with different heating temperature. Each FRS was added in lard and heated at 90, 120, 150, and 180°C for 48, 24, 8, or 2 h, respectively and antioxidant capacity was evaluated by conjugated dienoic acid (CDA) value, conjugated diene hydroperoxides, p‐anisidine value (p‐AV), and a modified 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) method. Apparent activation energy of sesamol was determined as 12.98 kcal/mol in a lard model system. Antioxidant capacity of sesamol was as good as that of TBHQ and was higher than those of BHA and α‐tocopherol at 90, 120, and 150°C based on CDA, conjugated diene hydroperoxides, and p‐AV assays. The results of a modified DPPH method showed that each FRS showed different distribution of radical scavenging compounds from oxidized lipids (RSOLs) during oxidation. Sesamol may replace synthetic FRSs like TBHQ and BHA in processed foods treated with high temperature. Practical application: Processed foods are frequently treated with high temperature during oven‐drying, roasting, baking, and deep‐fat frying. This study showed that sesamol, one of natural antioxidants, had stronger antioxidant capacities than other synthetic FRSs at the temperature ranges from 90 to 180°C. The results of this study can be applied in food industries producing deep‐fat fried foods including snacks, chips, and French fries to extend the shelf‐life of final foods with high temperature treatment.     

Anti-Rancidity Effects of Sesame and Rice Bran Oils on Canola Oil During Deep Frying

In this study, the effect of sesame oil (SEO) and rice bran oil (RBO) on the rancidity of canola oil (CAO) during the process of frying potato pieces at 180 °C was investigated. The SEO and RBO were added to the CAO at levels of 3 and 6%. Frying stability of the oil samples during the frying process was measured on the basis of total polar compounds (TPC) content, conjugated diene value (CDV), acid value (AV), and carbonyl value (CV). In general, frying stability of the CAO significantly (P < 0.05) improved in the presence of the SEO and RBO. The positive effect of the SEO on the stability of the CAO was more than that of the RBO. Increasing the amounts of SEO and RBO from 3 to 6% led to decreases in the TPC and AV, and increases in the CDV and CV of the CAO during the frying process. The best frying performance for the CAO was obtained by use of 3% of both SEO and RBO together (CAO/SEO/RBO, 94:3:3 w/w/w).     

Determination of hydroperoxides and structures by high-performance liquid chromatography with post-column detection with diphenyl-1-pyrenylphosphine

A high-performance liquid chromatographic method, using post-column detection with diphenyl-1-pyrenyl-phosphine (DPPP), was developed for the quantitative and qualitative determination of isomeric lipid hydroperoxides (OOH). The OOH eluted from a normal-phase column were passed through a photodiode array detector and then mixed with DPPP solution in a reaction coil heated at 80°C. DPPP oxide formed by the reaction with OOH was determined by monitoring the fluorescence intensity at 380 nm and excitation at 352 nm. The conjugated diene OOH (13-cis, trans- and 9-cis, trans-OOH) and nonconjugated OOH (12-cis-trans- and 10-cis, trans-OOH) from photosensitized oxidation of methyl linoleate were determined in a molar ratio of 31∶29∶19∶21, respectively. However, only the two conjugated hydroperoxides were detected by ultraviolet absorption at 234 nm. Further applications were carried out for the determination of OOH of methyl oleate and methyl linolenate. This method proved to be useful for the determination of the OOH containing both conjugated and nonconjugated diene structures.     

Autoxidation of methyl linoleate. Separation and analysis of isomeric mixtures of methyl linoleate hydroperoxides and methyl hydroxylinoleates

The mixture of conjugated diene hydroperoxide isomers obtained from autoxidation of methyl linoleate was separated by high performance liquid chromatography (HPLC). Four major isomers were obtained from adsorption chromatography and identified as the 9 and 13 positional isomers having thetrans-trans andcis-trans configurations. The latter geometrical isomers have thetrans double bond adjacent to the hydroperoxide group. The hydroxy compounds (methyl hydroxylinoleates) obtained from the hydroperoxides by NaBH₄ reduction were similarly separated but with improved resolution. This is the first instance of the complete separation of these compounds and provides a rapid method for their analysis. Unlike adsorption chromatography, reversed-phase chromatography separates the mixtures only according to the geometrical isomerism of the double bonds and not according to the position of the hydroxy or hydroperoxide function.     

Protective effect of olive oil and its phenolic compounds against low density lipoprotein oxidation

The protective effect of phenolic compounds from an olive oil extract, and of olive oils with (extra-virgin) and without (refined) phenolic components, on low density lipoprotein (LDL) oxidation was investigated. When added to isolated LDL, phenolics [0.025–0.3 mg/L caffeic acid equivalents (CAE)] increased the lag time of conjugated diene formation after copper-mediated LDL oxidation in a concentration-dependent manner. Concentrations of phenolics greater than 20 mg/L inhibited formation of thiobarbituric-acid reactive substances after AAPH-initiated LDL oxidation. LDL isolated from plasma after preincubation with phenolics (25–160 mg/L CAE) showed a concentration-dependent increase in the lag time of conjugated diene formation after copper-mediated LDL oxidation. Refined olive oil (0 mg/L CAE) and extra-virgin olive oil (0.1 and 0.3 mg/L CAE) added to isolated LDL caused an increase in the lag time of conjugated diene formation after copper-mediated LDL oxidation that was related to olive oil phenolic content. Multiple regression analysis showed that phenolics were significantly associated with the increase in lag time after adjustment for effects of other antioxidants; α-tocopherol also achieved a statistically significant effect. These results indicate that olive oil phenolic compounds protect LDL against peroxyl radical-dependent and metal-induced oxidation in vitro and could associate with LDL after their incubation with plasma. Both types of olive oil protect LDL from oxidation. Olive oil containing phenolics, however, shows more antioxidant effect on LDL oxidation than refined olive oil.     

Structure of hydroperoxides obtained from autoxidized methyl linoleate

Summary A sample of debromination methyl linoleate has been autoxidized to a peroxide value of 671 m.e./kg. at approximately 0°C. in the dark. An essentially pure concentrate of methyl octadecadienoate monohy-droperoxide was quantitatively separated; infrared and ultraviolet spectral studies were made on the peroxide concentrate and on the corresponding hydroxyl derivative obtained by reducing the peroxides with stannous chloride. The infrared data showed no conjugated peroxides having geometric configurations other than cis, trans; the same data also showed that the peroxide concentrate contained at least 90% conjugated cis,trans forms. Calculations based on ultraviolet spectrophotometric methods also indicated that the peroxides were at least 90% conjugated. The remaining 10% of the sample is most likely nonconjugated diene hydroperoxide. Since analogous cis, cis conjugated dienes have not been isolated and their infrared and ultraviolet properties are unknown, their presence here in small amounts is possible. Ultraviolet and infrared spectra of the reduced compounds conform closely to those of the peroxides except for reduction in the intensity of the OH bond at 2.88 μ. The infrared absorption spectra of the C−H structure and carbonyl groups of an essentially pure conjugated cis, trans methyl octadecadienoate monohydroperoxide were recorded, using a LiF prism. The infrared absorption spectra of the C−H strucfraction isolated from methyl linoleate autoxidized in the dark at 24°C. indicated that appreciable amounts of conjugated trans, trans hydroperoxides were present, in addition to those of the cis, trans type. It is possible that the conjugated cis, trans isomers were formed originally but were labile at the higher temperature and in the presence of catalysts (e.g., peroxides) were transformed to the thermodynamically more stable conjugated trans, trans isomer. This work was supported in part by a contract between the Office of Naval Research, Department of the Navy, and the University of Minnesota. Hormel Institute publication No. 81, and paper No. 133, Journal Series, General Mills Research Laboratories.