Frying Performance of Canola Oil Triacylglycerides as Affected by Vegetable Oils Minor Components

The endogenous minor components from canola, rice bran, sesame and palm oils including selected phospholipids, and various combinations of tocopherol isomers were tested during frying using canola oil triacylglycerols as the frying medium. Thermo-oxidative degradation was assessed by measurement of the total polar components, the rate of volatile carbonyl compounds and 4-hydroxynonenal formation. All the tested minor components protected to a different extent canola triacylglycerides from thermo-oxidative degradation during frying. No significant differences were observed in the protection of the triacylglycerides among all the tested tocopherol isomers and their mixtures. Irrespective of the composition of tocopherol homologous, an increase in the added amounts above 1,000 μg/g did not improve protection. Minor components isolated from rice bran and sesame oils offered better protection during canola triacylglycerides frying than endogenous minor components isolated from canola oil. When 0.2% phosphatidylcholine or phosphatidylethanolamine was added to the canola triacylglycerides, the amount of formed polar components decreased twice as compared to the tocopherol isomers. Accordingly, by optimizing the composition and the concentration of the endogenous minor components, the frying performance of oil can be significantly enhanced.     

Determination of squalene in olive oil using fractional crystallization for sample preparation

A simple, rapid method for the determination of squalene in virgin olive oil was developed using RP-HPLC with detection at 208 nm. Fractional crystallization from methanol/acetone (7∶3, vol/vol) was applied to obtain squalene in the liquid fraction of the oil prior to HPLC. Elution of squalene was then carried out isocratically with acetone/acetonitrile (40∶60 vol/vol) within 11 min. The detection limit was 23 mg/kg, and the limit of quantification 79 mg/kg. The precision of the crystallization procedure (CV%=3.76, n=7) and the mean recovery (92.5 and 81.5% for the 7,000 and 700 mg/kg levels of addition, respectively) were satisfactory. The method is easily applicable to fulfill future needs for nutrition labeling.     

Low-linolenic acid soybean oil—Alternatives to frying oils

Oil was hexane-extracted from soybeans that had been modified by hybridization breeding for low-linolenic acid (18∶3) content. Extracted crude oils were processed to finished edible oils by laboratory simulations of commercial oil processing procedures. Oils from three germplasm lines N83-375 (5.5% 18∶3), N89-2009 (2.9% 18∶3) and N85-2176 (1.9% 18∶3) were compared to commercial unhydrogenated soybean salad oil with 6.2% 18∶3 and two hydrogenated soybean frying oils, HSBOI (4.1% 18∶3) and HSBOII (<0.2% 18∶3). Low-18∶3 oils produced by hybridization showed significantly lower room odor intensity scores than the commercial soybean salad oil and the commercial frying oils. The N85-2176 oil with an 18∶3 content below 2.0% showed no fishy odor after 10 h at 190°C and lower burnt and acrid odors after 20 h of use when compared to the commercial oils. Flavor quality of potatoes fried with the N85-2176 oil at 190°C after 10 and 20 h was good, and significantly better at both time periods than that of potatoes fried in the unhydrogenated oil or in the hydrogenated oils. Flavor quality scores of potatoes fried in the N89-2009 oil (2.9% 18∶3) after 10 and 20 h was good and equal to that of potatoes fried in the HSBOI oil (4.1% 18∶3). Fishy flavors, perceived with potatoes fried in the low-18∶3 oils, were significantly lower than those reported for potatoes fried in the unhydrogenated control oil, and the potatoes lacked the hydrogenated flavors of potatoes fried in hydrogenated oils. These results indicate that oils with lowered linolenic acid content produced by hybridization breeding of soybeans are potential alternatives to hydrogenated frying oils.     

Frying stability of high-oleate and regular soybean oil blends

The objective of this work was to study the frying stability of soybean oil (SBO) with reduced linoleate (18∶2) and linolenate (18∶3) and elevated oleate (18∶1) contents. High-oleate SBO [HO SBO, 79% oleic acid (OA)] and a control (conventional SBO, 21.5% OA) were tested as is, as well as blended in different ratios to make three blended oils containing 36.9, 50.7, and 64.7% OA, abbreviated as 37%OA, 51%OA, and 65%OA, respectively. In addition, a low-linolenate (LL) SBO containing 1.4% 18∶3 and 25.3% 18∶1 was tested. Bread cubes (8.19 cm³) were fried in each of 18 oils (6 treatments×3 replicates). We hypothesized that stability indicators would be indirectly related to the total 18∶2 plus 18∶3 percentages and/or the calculated oxidizability. In general, the results were fairly predictable based on total 18∶2 and 18∶3 concentrations. The overall frying stability of the six oil treatments, from the best to the poorest, was: 79%OA, 65%OA, 51%OA, LL≥37%OA, and the control, with respective total compositions for 18∶2 plus 18∶3 of 10.3, 23.6, 36.3, 59.6, 48.9, and 62.8%. The greatly reduced concentration of 18∶3 in the LL SBO made it more stable than the 37%OA, even though the combined composition of 18∶2 and 18∶3 of LL was greater than that of the 37%OA. Blending conventional SBO with HO SBO had a profound effect on the oxidative stability index and color of the blended oils, but the values were not linearly predictable by the percentage of control in the blended oil. Other stability indices, including calculated oxidizability, calculated iodine value, conjugated dienoic acid value, and viscosity, changed in linear response to an increased proportion of the control in the blends.     

Modifications of butter stearin by blending and interesterification for better utilization in edible fat products

This work primarily aims to further modify the stearin fractions, obtained from anhydrous milk fat, after fractionation by dry process and by solvent process using isopropanol, for extending their scope of utilization in edible fat products. Butter stearin fractions, on blending with liquid oils like sunflower oil and soybean oil in different proportions, offer nutritionally important fat products with enriched content of essential fatty acids like C_18∶2 and C_18∶3. The butter stearin fraction from isopropanol fractionation, when interesterified with individual liquid oils by Mucor miehei lipase as a catalyst, yields fat products having desirable properties in making melange spread fat products with reasonable content of polyunsaturated fatty acids and almost zero trans fatty acid content.     

A kinetic study of oil deterioration during frying and a comparison with heating

The thermooxidative alterations of cottonseed oil during frying of potato chips without oil turnover, in a temperature range of 155–195°C, were studied. The results showed that the content of polar compounds, conjugated dienes, conjugated trienes, and p-anisidine value (p-AV) increased linearly with the time of frying at a rate depending on temperature. The rate constants showed a significant but low increase with temperature, except for the rate constant of conjugated trienes that was not correlated to frying temperature. The alterations induced by heating the oil were also measured and compared with those observed in frying at the same temperature. The major difference observed between frying and heating was related to the p-AV increase, which presented a considerably higher rate during heating. The FA content, as a function of process time during frying at 185°C, showed a significant increase in palmitic acid (C16∶0) and a significant decrease in linoleic acid (C18∶2). Oleic acid (C18∶1) also showed a small but significant decrease. The same results were obtained for the oil heated at 185°C. Examination of p-AV or conjugated dienes with polar compounds showed that both p-AV and conjugated dienes had a linear relationship with total polar compounds, with correlation coefficients of 0.946 and 0.862, respectively.     

Quenching mechanism and kinetics of ascorbyl palmitate for the reduction of the gamma irradiation-induced oxidation of oils

The effects of 0, 250, 500, and 1000 ppm (wt/vol) ascorbyl palmitate (AP) on the gamma irradiation-induced oxidation of soybean oil, cottonseed oil, corn oil, tallow, lard, or linoleic acid either in a solvent mixture (benzene/methanol, 4:1 vol/vol) or in methanol, was studied immediately after gamma irradiation with a dose of 1–5 kGy. Steady-state kinetic approximation was used to determine a quenching mechanism and quenching rate constant of AP on the gamma irradiation-induced oxidation of purified soybean oil in a solvent mixture (benzene/methanol, 4:1 vol/vol). Irradiation greatly increased oxidation of all oils, as was expected. AP was extremely effective at minimizing oxidation in all oils, and its effectiveness was concentration dependent. AP showed significantly greater antioxidative activity than α-tocopherol for the reduction of oxidation in all oils (P<0.05). The steady-state kinetic studies indicated that AP quenched oxygen only to minimize the oxidation of oils. The calculated total quenching rate of AP was 7.51×10⁷ M⁻¹s⁻¹. The present results clearly show the effective oxygen quenching ability of AP for the reduction of gamma irradiation-induced oxidation of oils.     

Oxidative stability of healthful frying oil medium and uptake of inherent nutraceuticals during deep frying

Four healthful frying oil mediums have been formulated using sunflower (FOB-I), groundnut (FOB-II), mustard (FOB-III), and palm olein (FOB-IV) oils as base oils, and fortified with rice bran and crude sesame oils separately in the ratio of 60∶20∶20 (by vol). Oxidative stabilities have been ascertained by deep-frying potato bajji (potato slices sandwiched with Bengal gram flour) continuously for 60 min for three cycles with a gap of 7 d each. The product had moisture between 12.8 and 16.0% and absorbed fat between 32.5 and 38.1%, making the oil media vulnerable to oxidation. The p-anisidine values for leftover FOB-I and FOB-IV ranged from 10.8 to 24.4 and from 1.5 to 10.7, respectively, indicating that the former was a less and the latter a more stable combination. Hydroperoxide and conjugated dienes were assessed by UV spectrometry at λ_max 230 nm. The O.D. was maximal (1.4) for FOB-I samples for both leftover and absorbed oils for third-cycle experiments. That there was no absorbance for the FOB-III and-IV samples indicated their absence. Estimation of oryzanol and sesamol in oil left over after deep frying and in the oil absorbed by the products indicated that distribution was equal and there was no loss of these active factors during deep frying. The study indicated that sunflower oil blend was the least stable and the palm olein blend was most stable.     

Cottonseed extraction with mixtures of acetone and hexane

Cottonseed flakes were extracted with mixtures of n-hexane and acetone, with the concentration of acetone varying between 10 and 75%. Adding small amounts of acetone (≤25%) to n-hexane significantly increased the extraction of free and total gossypol from cottonseed flakes. Sensory testing detected no difference in the odor of cottonseed meals produced either by extraction with 100% n-hexane or by extraction with a 10∶90 (vol/vol) mixture of acetone/hexane. More than 80% of the free gossypol was removed by the 10∶90 mixture of acetone/hexane, whereas pure n-hexane extracted about 47% of the free gossypol from cottonseed flakes. A solvent mixture containing 25% acetone removed nearly 90% of the free gossypol that was removable by extraction with pure acetone; the residual meal had only a minimal increase in odor. In contrast, cottonseed meals produced by extraction with pure acetone had a much higher odor intensity. The composition of the cottonseed crude oil was insignificantly affected by the acetone concentration of the extraction solvent. The results indicate that mixtures of acetone and n-hexane can be used as extraction solvents to produce cottonseed crude oil without the concomitant development of odorous meals.     

Low-temperature flow properties of vegetable oil/cosolvent blend diesel fuels

Vegetable oils are an attractive renewable source for alternative diesel fuels. However, the relatively high kinematic viscosity of vegetable oils must be reduced to make them more compatible with conventional compression-ignition engines and fuel systems. Cosolvent blending is a low-cost and easy-to-adapt technology that reduces viscosity by diluting the vegetable oil with a low-M.W. alcohol (methanol or ethanol). The cosolvent (A), which consists of one or more amphiphilic compounds, is added to solubilize the otherwise nearly immiscible oil-polar alcohol mixture. This work investigates cold flow properties and phase equilibrium behavior associated with blends consisting of soybean oil (SBO) and methanol where A=8∶1 (mol) n-butanol/oleyl alcohol; 6∶1 (mol) 2-octanol/triethylammonium linoleate; and 4∶1 (mol) 2-octanol/Unadol 40 (alcohols from SBO FA); and a blend of 2∶1 (vol/vol) No. 2 diesel fuel/SBO and 95% ethanol where A=n-butanol. Cloud point (CP), pour point, cold filter plugging point (CFPP), and low-temperature flow test (LTFT) results were compared with corresponding phase separation temperature (T _ϕ) data measured at equilibrium. Although CP data were measured under non-equilibrium experimental conditions, a nearly linear correlation was found between T _ϕ and CP. Statistical analysis showed that T _ϕ may also be correlated with CFPP and LTFT. Analysis of heating and cooling DSC curves indicated that peak temperatures may be employed to predict cold flow properties and T _ϕ behavior for SBO/cosolvent blends. Cooling curve parameters correlated more readily than heating curve parameters. Finally, relatively low quantities of heat evolved during freezing indicated that crystallization in the SBO/cosolvent blends studied in this work occurs easily during cooling.     

A multivariate optimization of triacylglycerol analysis by high-performance liquid chromatography

In the present study we have used statistical experimental design and multivariate optimization to formally optimize a reversed-phase high-performance liquid chromatography method for the analysis of triacylglycerol molecular species of natural oils. The optimal conditions found were, on an octadecylsilan-column, from acetonitrile/isooctane (90∶10, vol/vol) to acetonitrile/ethanol/isooctane (40∶35∶25, by vol), at a column temperature of 50°C and a flowrate of 1.5mL/min using a negative exponential gradient profile. Several examples of separations of natural seed and animal oils,i.e., soybean oil, rapeseed oil, palm oil, linseed oil, tallow and fish oil, are given. A version of the equivalent carbon number concept, utilizing the Snyder polarity index, was used to identity the molecular species.     

Effect of a modified deep-fat fryer on chemical and physical characteristics of frying oil

We designed a modified deep-fat fryer (MDF) to have a smaller oil area (A) relative to depth or height (H) such that H/√A=0.93. The modification was intended to retard the thermal degradation of the frying oil and the production of waste oil. Frozen croquettes were fried in vegetable oil using the MDF (H/√A=0.93) and three conventional deep-fat fryers (CDF1, H/√A=0.25; CDF2, H/√A=0.20; CDF3, H/√A=0.30) at 180°C for 72 h at 8 h/d. Frying oils were periodically collected, and their chemical and physical characteristics were examined. The acid value (AV) of frying oils used for 72 h in the MDF was lower than that for oils used in the CDF, although the AV was similar in all fryers until 32 h. The oil deep-fried with MDF had a higher degree of color than that with CDF until 48 h. Polymerized materials and the carbonyl value of frying oil after heating 72h with MDF were lower than those with CDF. The residual tocopherol content of frying oil with MDF was 83% of the content in fresh oil, whereas with CDF the tocopherol contents were less than 63%. The oil consumption by MDF was less than that by CDF, although the turnover rate was higher in MDF than in CDF. These results suggest that during deep-fat frying the MDF may retard the thermal deterioration of vegetable oils and generate less waste oil.     

Antioxidant activity of extracts of defatted seeds of niger (<Emphasis Type="Italic">Guizotia abyssinica</Emphasis>)

Niger (Guizotia abyssinica) seed was ground and then defatted with hexane. The meal remaining after oil extraction was tested as a source of antioxidants. Three solvent systems, A [80∶20 (vol/vol) ethanol/water], B [80∶20 (vol/vol) acetone/water], and C (water) were evaluated as extraction media. Crude extracts were examined for their antioxidant activity in a β-carotene-linoleate and a meat model system. Extract A exhibited superior antioxidant activity, compared to extracts B and C, and its composition was studied further by using column chromatography and HPLC. Four fractions (I–IV) were obtained, of which fractions III and IV showed activity in the β-carotene-linoleate model system. Fraction IV was also highly effective in scavenging the 2,2-diphenyl-1-picrylhydrazyl radical but was less active when used in a bulk oil model system. Preparative TLC showed fraction IV as consisting of two components. UV spectroscopy suggested that the major active component pressent was a chlorogenic acid-related compound. Furthermore, HPLC analysis established that chlorogenic acid was dominant in the free phenolics fraction (2.6 mg/g). Upon hydrolysis, however, a substantial amount of caffeic acid (42.8 mg/g) was released, presumably from esterified and glycosylated chlorogenic acid. Thus, niger extracts derive their antioxidant activity, at least in part, from the chlorogenic acid-related compounds.     

Isolation and detection of alkaline contaminant materials (ACM) in used frying oils

Alkaline contaminant materials are formed in frying oils during cooking. The ACM can be eluted from the same International Union of Pure and Applied Chemists-Association of Official Analytical Chemists (IUPACAOAC) silica gel column used to determine polar materials in frying oils. The ACM are eluted with methanol after “non-polar” and “polar” fractions already have been eluted from the column. A residue of silica gel in the methanol eluate must be insolubilized before the ACM can be identified and quantitated. IR was used to identify sodium oleate as the major constituent of ACM from a set of restaurant generated frying oil samples.     

Cyclic FA monomers in high-oleic acid sunflower oil and extra virgin olive oil used in repeated frying of fresh potatoes

The measurement of FA profile, polar material, oligomers, oxidized triacylglycerols (OTG), total polyphenols, and cyclic FA monomers (CFAM) was used to evaluate the alteration of a high-oleic sunflower oil (HOSO) and an extra virgin olive oil (EVOO) used in 75 domestic fryings of fresh potatoes with frequent replenishment (FR) of unused oil. CFAM were absent in the unused EVOO but appeared in small amounts in the unused HOSO. Although polar material, oligomers, OTG, and CTAM contents increased and linoleic acid and polyphenols content decreased in both oils during repeated frying, the changes produced should be considered small and related to the use of very stable oils and FR. Throughout the 75 fryings, the total CFAM concentration was higher in HOSO than in EVOO. OTG increased more quickly in EVOO, whereas oligomers increased more quickly in HOSO. Polar material and oligomer content appear significantly correlated (r=0.9678 and r=0.9739, respectively; for both, P<0.001) with the CFAM content. A 25% polar material and 12% oligomer content would correspond to about 1 mg·kg⁻¹ oil of CFAM. Data suggest that both oils, particularly EVOO, perform very well in frying, with a low production of oligomers, polar materials, and CFAM.     

Effect of extraction methods on lipid yield and fatty acid composition of lipid classes containing γ-linolenic acid extracted from fungi

The effect of extraction procedures on the lipid yield and fatty acid composition of total lipid and main lipid structures (phospholipids, diacylglycerols, triacylglycerols, free fatty acids, and sterol esters) of fungal biomass (Mucor mucedo CCF-1384) containing γ-linolenic acid (GLA) was investigated. Seventeen extraction methods, divided into three groups, were tested: six with chloroform/methanol, five with hexane/alcohols, and six with common solvents or mixtures. The chloroform/methanol procedure (2∶1) was selected as standard, where lipid yield (TL/DCW, total lipid per dry cell weight) was 17.8%, considered to be 100% of lipids present. All chloroform/methanol extractions yielded more than 83% recorvey of lipids. Use of hexane/isopropanol solvent systems led to a maximum of 75% recovery. The best lipid yield was achieved by a two-step extraction with ethanol and hexane (120%). Extraction efficiency of the other solvent systems reached a maximum of 73%. Triacylglycerols were the main structures of lipid isolated; only methanol-extracted lipid contained 58.5% phospholipids. The fatty acid content of total recovered lipid was variable and depended on both the lipid class composition and the solvent system. GLA concentrations in total lipids isolated by hexane/alcohol procedures (7.3–10.7%) are comparable with classical chloroform/methanol systems (6.5–10.0%). The maximal GLA yield was obtained with chloroform/methanol/n-butanol/water/0.1 M ethylenediaminetetraacetic acid (EDTA) (2∶1∶1∶1∶0.1, by vol) and after two-step extraction with ethanol and hexane (14.3 and 13.7 g GLA/kg DCW, respectively). The highest GLA content was analyzed in the phospholipid fraction (16.1%) after using chloroform/methanol/n-butanol/water/0.1 M EDTA (2∶1∶1∶1∶0.1, by vol). Remarkably low concentrations of polyunsaturated fatty acids were determined in the free fatty acid fraction.     

Analysis of free and esterified sterols in vegetable oils

In vegetable oils, phytosterols occur as free sterols or as steryl esters. Few analytical methods report the quantification of esterified and free sterols in vegetable oils. In this study, esterified and free sterols were separated by silica gel column chromatography upon elution with n-hexane/ethyl acetate (90∶10 vol/vol) followed by n-hexane/diethyl ether/ethanol (25∶25∶50 by vol). Both fractions were saponified separately and the phytosterol content was quantified by GC. The analytical method for the analysis of esterified and free sterols had a relative standard deviation of 1.16% and an accuracy of 93.6–94.1%, which was comparable to the reference method for the total sterol analysis. A large variation in the content and distribution of the sterol fraction between different vegetable oils can be observed. Corn and rapeseed oils were very rich in phytosterols, which mainly occurred as steryl esters (56–60%), whereas the majority of the other vegetable oils (soybean, sunflower, palm oil, etc.) contained a much lower esterified sterol content (25–40%). No difference in the relative proportion of the individual sterols among crude and refined vegetable oils was observed.     

Impact of Canolol‐Enriched Extract from Heat‐Treated Canola Meal to Enhance Oil Quality Parameters in Deep‐Frying: a Comparison with Rosemary Extract and TBHQ‐Fortified Oil Systems

Canolol‐enriched extracts obtained from the extraction of fluidized bed treated canola meal with supercritical carbon dioxide were added to high‐oleic canola oil in different concentrations (200, 500 and 750 mg/kg). After 30 h of deep‐fat frying, oils fortified with canolol‐enriched extracts showed a two to three times better frying performance in comparison to the commonly used antioxidants (TBHQ, 200 mg/kg; rosemary extract, 40 and 200 mg/kg) and a control without antioxidants with regards to the formation of di‐ and polymer triacylglycerols, total polar compounds, secondary degradation products (anisidine value) and the iodine value. The canolol‐enriched extracts were also able to slow down the degradation of α‐ and γ‐tocopherol during frying resulting in significant amounts of tocopherols after 30 h of frying in comparison to the other oils. The influence of the canolol‐enriched extracts indicated strongly concentration‐dependent performance. With increasing concentration of the extract, the thermal stability of the fortified oil was improved. The only disadvantage of the addition of the extracts was an increase in the initial acid value, but within the frying time, only oil fortified with 750 mg canolol‐enriched extract/kg reached the limit given in different countries.     

Chromatographic separation of glucopyranosyl sinapate from canola meal

The compound 1-O-β-D glucopyranosyl sinapate (GPS), a phenolic glycoside, was separated from ethanolic extracts of defatted canola meal by a two-step chromatographic method. The first step involved Sephadex LH-20 chromatography with methanol as the eluting solvent. The solvent from the fraction containing GPS was evaporated, and glucopyranosyl sinapate was subsequently separated by a semi-preparative high-performance liquid chromatography method with an RP-18 column and a mobile phase consisting of water/acetonitrile/acetic acid (88∶10∶2, vol/vol/vol).     

Quenching mechanism and kinetics of ascorbyl palmitate for the reduction of the photosensitized oxidation of oils

Effects of 0, 500, 1000, and 1500 ppm (wt/vol) ascorbyl palmitate (AP) on the methylene-blue- and the chlorophyll-sensitized photooxidations of linoleic acid or soybean oil, either in methanol or in a solvent mixture (benzene/methanol, 4:1, vol/vol), were studied during storage under 3300 lux fluorescent light for 5 h. Steady-state kinetic approximation was used to determine a quenching mechanism and quenching rate constant of AP in the chlorophyll-sensitized photooxidation of methyl linoleate in a solvent mixture (benzene/methanol, 4:1, vol/vol). Both methylene blue and chlorophyll greatly increased the photooxidation of linoleic acid and soybean oil, as was expected. AP was extremely effective at minimizing both methylene-blue-and chlorophyll-sensitized photooxidations of linoleic acid and soybean oil, and its effectiveness was concentration-dependent. The addition of 500, 1000, and 1500 ppm AP resulted in 69.3, 83.6, and 94.6% inhibition of methyleneblue-sensitized photooxidation of linoleic acid, respectively, after 5-h storage under fluorescent light. AP showed significantly greater antiphotooxidative activity than α-tocopherol for the reduction of methylene blue-sensitized photooxidation of linoleic acid (P < 0.05). The steady-state kinetic studies indicated that AP quenched singlet oxygen only to minimize the chlorophyll-sensitized photooxidation of oils. The calculated total quenching rate of AP was 1.0 × 10⁸ M⁻¹s⁻¹. The present results clearly showed, for the first time, the effective singlet oxygen quenching ability of AP for the reduction of photosensitized oxidation of oils.