Performance of Regular and Modified Canola and Soybean Oils in Rotational Frying

Canola and soybean oils both regular and with modified fatty acid compositions by genetic modifications and hydrogenation were compared for frying performance. The frying was conducted at 185 ± 5 °C for up to 12 days where French fries, battered chicken and fish sticks were fried in succession. Modified canola oils, with reduced levels of linolenic acid, accumulated significantly lower amounts of polar components compared to the other tested oils. Canola oils generally displayed lower amounts of oligomers in their polar fraction. Higher rates of free fatty acids formation were observed for the hydrogenated oils compared to the other oils, with canola frying shortening showing the highest amount at the end of the frying period. The half-life of tocopherols for both regular and modified soybean oils was 1–2 days compared to 6 days observed for high-oleic low-linolenic canola oil. The highest anisidine values were observed for soybean oil with the maximum reached on the 10th day of frying. Canola and soybean frying shortenings exhibited a faster rate of color formation at any of the frying times. The high-oleic low-linolenic canola oil exhibited the greatest frying stability as assessed by polar components, oligomers and non-volatile carbonyl components formation. Moreover, food fried in the high-oleic low-linolenic canola oil obtained the best scores in the sensory acceptance assessment.     

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).     

Frying Stability of Canola Oil Blended with Palm Olein, Olive, and Corn Oils

The fatty acid composition, peroxide value (PV), acid value (AV), iodine value (IV), total tocopherols (TT) content, and total phenolics (TP) content of canola oil (CAO), palm olein oil (POO), olive oil (OLO), corn oil (COO), and the binary and ternary blends of the CAO with the POO, OLO, and COO were determined. The blends were prepared in the volume ratios of 75:25 (CAO/POO, CAO/OLO, CAO/COO) and 75:15:10 (CAO/POO/OLO, CAO/POO/COO). The CAO and its blends were used to fry potato pieces (7.0 × 0.5 × 0.3 cm) at 180 °C. During the frying process, the total polar compounds (TPC) content, AV, oil/oxidative stability index (OSI), and color index (CI) of the CAO/blends were measured. In general, frying stability of the CAO was significantly (P < 0.05) improved by the blending, and the frying performance of the ternary blends was found to be better than that of the binary blends.     

Phytostanol Supplementation Through Frying Dough in Enriched Canola Oil

The objectives of this study were to determine a suitable level of phytostanols for addition to canola oil and to investigate the performance of the supplemented oil during frying. The frying oil was supplemented with 5, 10, 15, 20 % w/w phytostanols and two suitable levels (5 and 10 %) were selected. Dough frying was performed for 5 consecutive days at 180 °C for 5 h/day. The ranges of analytical measurements in the treatment groups were; free acidity (0.12–10.07 %), conjugated dienes (0.47–1.37 %), total polar material with probe (9.00–51.25 %), viscosity (46.27–195.51 cP), turbidity (0.82–1.80 NTU), and smoke point (202.75–274.25 °C). The results indicated that 5 % phytostanol enriched oil was superior in terms of oil stability and sensory quality of the fried dough among all the enriched oils. Samples with 10 % added phytostanols were high in free acidity, conjugated dienes and smoke points. Sterol composition analysis showed that the fried dough absorbed total sterols of 49.9 and 95 g/kg in 5 and 10 % supplemented oils, respectively. Hence, some health benefits could be achieved through consuming products which have been fried in phytostanol supplemented canola oil.     

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.     

Minor Components in Canola Oil and Effects of Refining on These Constituents: A Review

Crude canola oil is composed mainly of triacylglycerols but contains considerable amounts of desirable and undesirable minor components. Crude canola oil is refined in order to remove undesirable minor compounds that make this oil unusable in food products. However, refining can also cause the removal of desirable health-promoting minor components from the oil. The first section of this review describes the chemical composition of canola oil, followed by a brief introduction to the effects of minor components on canola oil quality and stability. Following a review of traditional canola oil refining methods, the effects of individual refining stages on the removal of both desirable and undesirable components from canola oil are presented and contrasted with other common vegetable oils.     

Minor Constituents in Canola Oil Processed by Traditional and Minimal Refining Methods

The minimal refining method described in the present study made it possible to neutralize crude canola oil with Ca(OH)₂, MgO, and Na₂SiO₃ as alternatives to NaOH. After citric acid degumming, about 98 % of the phosphorous content was removed from crude oil. The free fatty acid content after minimal neutralization with Ca(OH)₂ decreased from 0.50 to 0.03 %. Other quality parameters, such as peroxide value, anisidine value, and chlorophyll content, after traditional and minimal neutralization were within industrial acceptable levels. The use of Trisyl silica and Magnesol R60 made it feasible to remove the hot-water washing step and decreased the amount of residual soap to <10 mg/kg oil. There were no significant changes in chemical characteristics of canola oil after using wet and dry bleaching methods. During traditional neutralization, the total tocopherol loss was 19.6 %, while minimal refining with Ca(OH)₂, MgO, and Na₂SiO₃ resulted in 7.0, 2.6, and 0.9 % reductions in total tocopherols. Traditional refining removed 23.6 % of total free sterols, while after minimal refining free sterols content did not change. Both traditional and minimal refining resulted in almost complete removal of polyphenols from canola oil. Total phytosterols and tocopherols in two cold-pressed canola oils were 774 and 836 mg/100 g, and 366 and 354 mg/kg, respectively. The minimal refining method described in the present study was a new practical approach to remove undesirable components from crude canola oil meeting commercial refining standards while preserving more healthy minor components.     

Recognition of Adulterated Oils by Direct Analysis of the Minor Components

Recognition of adulteration by other oils via direct analysis of the minor components (“sterol fraction”) is shown for olive oil. 10 % of various oils were admixed, the free alcohols silylated and the minor components analyzed by on-line coupled LC-GC-FID. For most oils, even smaller additions can be recognized. Admixed oils can no longer be determined, however, if their minor components have been removed by strong raffination. Bleaching of rapeseed oil with 7% of earth at 180 °C, in fact, completely removed free and esterified sterols.     

Minor Components in Vegetable Oil Methyl Esters I: Sterols in Rape Seed Oil Methyl Ester

Rape seed oil methyl ester (RME), a diesel fuel substitute and a technical product of increasing importance, contains a number of minor components, which may influence its technical properties in various ways, Sterols, the main constituents of the unsaponifiable matter in rape seed oil, represent an important group of such minor components, which are then found in rape seed oil methyl ester. The concentration and composition of the total sterols in the fraction of unsaponifiables were determined in several RME samples of different origin by the usual procedure of saponification and isolation of the sterol fraction, followed by gas chromatographic analysis. The concentration and composition of the free sterols present in RME and the content of sterol esters were also determined by on-line LC-GC. The total sterol content in the RME samples varied between 0.70% and 0.81%. The sterol fraction of RME composed as follows: 0.4% cholesterol, 9.0% brassicasterol, 37.7% campesterol, 0.4% stigmasterol, 48.0% β-sitosterol, 2.8% Δ⁵-avenasterol, and 0.5% Δ⁷-stigmasterol. By on-line LC-GC 0.24-0.34% free sterols and 0.55-0.71% sterol esters have been found in the RME samples.     

Deterioration Kinetics of Crude Palm Oil,Canola Oil and Blend During Repeated Deep-Fat Frying

The oxidation of vegetable oils is generally treated as an apparent first order kinetic reaction. This study investigated the deterioration of crude palm oil (CPO), refined canola oil (RCO) and their blend (CPO:RCO 1:1 w/w) during 20 h of successive deep‐fat frying at 170, 180 and 190 °C. Kinetics of changes in oil quality indices, namely, free fatty acid (FFA), peroxide value (PV), anisidine value (p‐AV), total polar compounds (TPC) and color index (CI) were monitored. The results showed that FFA and PV accumulation followed the kinetic first order model, while p‐AV, TPC and CI followed the kinetic zero order model. The concentration and deterioration rate constants k, increased with increasing temperatures. This effect of temperature was modeled by the Arrhenius equation. The results showed that PV had the least activation energies E_a (kJ/mol) values of 5.4 ± 1 (RCO), 6.6 ± 0.7 (CPO) and 11.4 ± 1 (blend). The highest E_a requirement was exhibited by FFA with a range of 31.7 ± 3–76.5 ± 7 kJ/mol for the three oils. The overall E_a values showed that the stability of the blend was superior and not just intermediate of CPO and RCO. The correlation of the other oil quality indices with TPC indicated a positive linear correlation. The p‐AV displayed the strongest correlation, with mean correlation coefficient r_s of 0.998 ± 0.00, 0.994 ± 0.00 and 0.999 ± 0.00 for CPO, RCO and blend, respectively.     

Ricinoleic Acid in Common Vegetable Oils and Oil Seeds

An original gas chromatography/mass spectrometry method for quantifying trace amounts of ricinoleic acid (12-hydroxy-cis-9-octadecenoic acid) is detailed. Data are presented on trace amounts of ricinoleic acid found in several common vegetable oils and oils extracted from common oil seeds: e.g., ca. 30 ppm in commercial olive oil was the lowest amount; and ca. 2,690 ppm in oil extracted from cottonseeds was the highest amount.     

Rapid Assessment of Frying Performance Using Small Size Samples of Oils/Fats

A rapid, effective test mimicking actual frying was developed to assess the frying performance of oils and fats using small size samples. To a small volume of the oil to be tested, a formulated food consisting of gelatinized potato starch, glucose and silica gel (4:1:1 w/w) were added and content heated at 185 ± 5 °C with mixing for 2 h. Thermo-oxidative degradation of the oil was assessed by the measurement of the total amount of polar components and their composition, including degradation of tocopherols. The developed fast test accurately mimics actual frying done using an institutional fryer as assessed by the accumulation and composition of total polar components and the amount of residual tocopherols. The validity of the test was assessed using the following oils: regular canola, high oleic– low linolenic canola, and high oleic sunflower. Comparison of data between the fast frying test and institutional frying revealed a lack of significant differences. The developed frying test provides reliable quantitative and qualitative data describing the performance of the frying oil/fat. The rapid frying procedure allows assessment of the frying performance of oils at the early stages of development where usually only small amounts of the sample are available and when a large number of samples have to be tested assessing effects of oil additives.     

不同植物油甲酯生物柴油的润滑性能

利用大豆油、菜籽油、蓖麻油、玉米油为原料,通过酯交换法分别制备出生物柴油,利用红外光谱对其进行表征,然后用高频往复摩擦磨损试验机分别对生物柴油进行润滑性能测试,并与0#柴油进行对比,最后利用3D激光显微镜分别对其磨斑表面进行表征,测试结果表明,所有生物柴油的润滑性能要优于0#柴油,且菜籽油合成的生物柴油具有最优的综合性能。     

Temperature Dependence of HNE Formation in Vegetable Oils and Butter Oil

The temperature dependence of the formation of toxic 4-hydroxy-2-trans-nonenal (HNE) was investigated in high and low linoleic acid (LA) containing oils such as corn, soybean and butter oils. These oils contain about 60, 54 and 3–4% of LA for corn, soybean and butter oils, respectively. The oils were heated for 0, 0.5, 1, 2, and 3 h at 190 °C and for 0, 5, 15 and 30 min at 218 °C. HNE concentrations in the oils were analyzed by high performance liquid chromatography (HPLC). The maximum HNE concentrations in heated (190 °C) corn, soybean and butter oils were 5.46, 3.73 and 1.85 μg HNE/g oil, respectively. The concentration of HNE at 218 °C increased continuously for all the three oils, although they were heated for much shorter periods compared to the lower temperature of heating (190 °C). HNE concentration at 30 min reached the maximum of 15.48, 10.72 and 6.71 μg HNE/g oil for corn, soybean and butter oils, respectively. HNE concentration at higher temperature (218 °C) was 4.9, 3.7, and 8.7 times higher than at the lower temperature (190 °C) and 30 min of heating for corn, soybean and butter oils, respectively. It was found that HNE formation was temperature dependant in the tested oils.     

The Effects of Microwave Frying on Physicochemical Properties of Frying and Sunflower Oils

Deep fat frying is a method of food preparation which has been popular for quite a number of years. During deep frying, the quality of oil and the finished product decreases as the result of heat treatment of the oil exposed to air at high temperature. Application of heat by microwave as an alternative to the conventional method of frying has become popular in recent years. In this research, the effects of microwave frying on the changes in the quality indices of used oil have been investigated. To achieve this, potato slices were fried in both frying and sunflower oils by application of medium power microwave (550 W) for 20 min, three times a day, for five consecutive days, and oils were sampled for analysis. The results obtained from the chemical tests demonstrated that used frying oil had lower polar compounds, a higher induction period, and more saturated fatty acids than sunflower oil. The interesting point observed was that peroxides formed as the result of oxidation chain reactions were not broken down and were built up due to the lower temperature and shorter period of frying. Therefore microwave frying might be considered as a suitable alternative to the conventional frying due to less degradation of the oil and consequently a lower production of artifacts.     

Radical Scavenging Activity and Performance of Novel Phenolic Antioxidants in Oils During Storage and Frying

Novel phenolic antioxidants: 2a (6′-hydroxy-2′,5′,7′,8′-tetramethylchroman-2′-yl)methyl 3-methoxy-4-hydroxycinnamate, 2b (6′-hydroxy-2′,5′,7′,8′-tetramethylchroman-2′-yl)methyl 3,5-dimethoxy-4-hydroxycinnamate, 2c (6′-hydroxy-2′,5′,7′,8′-tetramethylchroman-2′-yl)methyl 3,4-dihydroxycinnamate, and 3 (6-hydroxy-2,5,7,8-tetramethylchroman-2-yl)methyl (6′-hydroxy-2′,5′,7′,8′-tetramethylchroman-2′-carboxylate) have been prepared in good yields and fully characterized by ¹H and ¹³C NMR, and HRMS. Their radical scavenging activities have been evaluated by DPPH and ORAC assays. Each of the synthesized antioxidants exhibited significantly higher radical scavenging activities than trolox and α-tocopherol. These novel antioxidants efficiently protected canola oil triacylglycerides (CTG) during accelerated storage and frying. Compounds 2c and 3 were significantly more efficient than α-tocopherol protecting CTG under accelerated storage. All new antioxidants were more efficient than α-tocopherol under frying conditions and present significantly higher thermal stability.     

Characterization of Aegean Olive Oils by Their Minor Compounds

This study presents a combined approach of establishing cultivar differences between Aegean olive oils, obtained from economically important olive oil producing cultivars (cv. Ayvalik and Memecik), based on chemometric evaluation of their content and in particular composition of the minor compounds. Evaluation of minor compounds with principal component analysis and linear discriminant analysis (LDA) indicated differentiation according to the cultivars. LDA produced a 100% correct group classification. Moreover, stigmasterol, apparent β-sitosterol and total sterols were found to have the highest discriminating power. Memecik oils were characterized by the highest content of antioxidant compounds (α-tocopherol, phenolic compounds and total phenolic compounds). On the other hand, Ayvalik oil had the highest level of total sterols. The data were analyzed statistically to evaluate the differences according to variety and crop season. The minor compounds of Ayvalik and Memecik oils presented statistically significant differences (p < 0.01) according to variety, except for the hydroxytyrosol and clerosterol content. The amount of α-tocopherol, total phenolic compounds, apparent β-sitosterol and total sterols varied with respect to crop season. A good correlation was observed between the amount of α-tocopherol, total phenolic compounds, apparent β-sitosterol and total sterols and some climatic variables.     

Phase Transition of Sunflower Oil as Affected by the Oxidation Level

The influence of the oxidation level on the phase transition behavior of sunflower oil was evaluated by differential scanning calorimetry (DSC) and synchrotron X-ray diffraction (XRD) at both small and wide angles. The crystallization was monitored at a cooling/heating rate of 2 °C/min from 20 to ?80 °C and vice versa applying both techniques. The triacylglycerols organize in two double-chain length structures: α 2L (61.87 Å) and β′ 2L (82.89 Å). The crystalline structure changes upon oxidation. In particular, the intensity of the XRD peak associated with the double-chain structure of β′, as well as its crystallization and melting enthalpy, significantly decreases as the oxidation level increases.