Cyclic fatty acids in sunflower oils during frying of frozen foods with oil replenishment

Frying of frozen foods has become popular because it considerably reduces cooking time. Polymers and cyclic fatty acid monomers (CFAM) formed during frying are potentially toxic and therefore their production should be minimized. Twenty discontinuous fryings of different frozen foods were carried out over ten consecutive days, in sunflower oil (SO) and in high‐oleic acid sunflower oil (HOSO), by adding fresh oil after each frying to bring the volume of the fryer oil back to 3 L. CFAM methyl ester derivates were hydrogenated, isolated, concentrated and quantified by HPLC using a reverse‐phase column, followed by gas chromatography. After 20 fryings, significantly higher contents of polar material, polymers and CFAM (all p <0.001) were found in SO than in HOSO. Bicyclic compound formation was four times higher in SO (p <0.001). The fat from the fried potatoes presented a polymer content very similar to that of their corresponding oils. The 100‐g rations of the SO‐fried potatoes from the 20^th frying supply 49 or 15%, respectively, more polymers and CFAM and 1 mg more bicyclic fatty acids than the 100‐g rations of HOSO‐fried potatoes. Because digestion and absorption of polar material, polymers and CFAM occur, the data clearly show the advantageousness and advisability of frying with HOSO rather than SO.     

Thermoxidative and hydrolytic changes in sunflower oil used in fryings with a fast turnover of fresh oil

The modification of a sunflower oil used for 75 repeated deep-fat fryings of potatoes, with a fast turnover of fresh oil during frying, was evaluated by measuring the total polar components isolated by column chromatography. The total polar components increased rapidly during the first 20 fryings from 5.09±0.21 (mean±SD) mg/100 mg unused oil to 15.99±0.40, followed by minor but also significant changes until the thirtieth frying (17.99±0.41 mg/100 mg oil). The level did not increase further with continued frying. Further, the polar fraction was examined by high-performance size-exclusion chromatography. Triglyceride polymers increased from 0.10±0.01 mg/100 mg unused oil to 1.65±0.13 and 3.44±0.17 mg/100 mg oil at the twentieth and seventy-fifth fryings, respectively. Triglyceride dimers also increased significantly from 0.75±0.12 mg/100 mg unused oil to 6.25±0.28 (mg/100 mg oil) at the twentieth frying and to 7.09±0.31 mg/100 mg oil at the thirtieth frying, with no further significant changes. Oxidized triglycerides also significantly increased, but at the twentieth frying reached a near-steady state of 6.26 mg/100 mg oil. Diglycerides and free fatty acid levels, related to hydrolytic alteration, did not increase with continued fryings. The results indicate that during deep-fat frying of potatoes with fast turnover of fresh sunflower oil, more thermoxidative than hydrolytic processes take place. A dramatic leap of total polar content and a change of compounds related to thermoxidative alteration of the oil were found during the first twenty fryings, followed by minor changes and by a tendency to reach a near-steady state throughout the successive fryings.     

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.     

High-performance size-exclusion chromatographic studies on a high-oleic acid sunflower oil during potato frying

The behavior of a high-oleic acid sunflower oil used for 75 repeated deep-fat fryings of potatoes, with a fast turnover of fresh oil during frying, was evaluated by measuring the total polar content isolated by column chromatography. The total polar content increased in the oil from 3.6 ± 0.1 (mean ± SD) mg/100 mg unused oil to 7.6 ± 0.4 mg/100 mg oil after being used in 20 repeated fryings, followed by a tendency to reach a near-steady state throughout the successive fryings. Further, the polar fraction was examined by high-performance size-exclusion chromatography. Triacylglyceride dimers increased continuously from 0.18 ± 0.01 mg/100 mg unused oil to 2.42 ± 0.12 mg/100 mg oil at the 40th frying with no further significant changes. The amount of triacylglyceride polymers increased from 0.03 ± 0.00 mg/100 mg unused oil to 0.70 ± 0.01 mg/100 mg oil at the 60th frying, but did not increase further with continued frying. Oxidized triacylglycerides also significantly increased from 1.13 ± 0.06 mg/100 mg oil to 3.58 ± 0.09 mg/100 mg oil at the 50th frying to reach a near-steady state in successive fryings. Diacylglycerides and free fatty acids levels, related to hydrolytic alteration, did not change from the starting oil after continued fryings. Data from this study indicated that repeated fryings of potatoes in high-oleic sunflower oil with a frequent turnover of fresh oil throughout the frying slightly increased the level of polar material in the fryer oil during the first fryings, followed by minor changes and a tendency to reach a near-steady state in successive fryings.     

High-performance size-exclusion chromatographic studies on polar components formed in sunflower oil used for frying

Thermoxidative and hydrolytic alterations of a sunflower oil used in sixty repeated and discontinuous deep-fat fryings of potatoes were evaluated by column and high-performance size-exclusion (HPSE) chromatography. Successive fryings of potatoes in sunflower oil, without turnover of fresh oil during the performance of fryings, increased the level of total polar components in the oil from 3.75% to 27.28% (w/w). Triglyceride polymers, triglyceride dimers, oxidized triglycerides and diglycerides increased after sixty fryings 89.8, 21.8, 4.9 and 1.7 times, respectively. These increases were well correlated with the number of fryings. However, there was not significant correlation between levels of free fatty acids and the number of fryings. Polar compounds were highly (r=0.9691) and significantly (P<0.01) correlated with triglyceride polymers and also highly (r=0.9969 and r=0.9738) and significantly (P<0.01) with triglyceride dimers and oxidized triglycerides, respectively. Nevertheless polar compounds were not significantly correlated with free fatty acids. Data suggest that an intensive thermoxidative rather than a hydrolytic process takes place in experimental deep-fat frying of potatoes.     

Performance of sunflower oil with high levels of oleic and palmitic acids during industrial frying of almonds,peanuts, and sunflower seeds

High-oleic, high-palmitic sunflower oil (HOHPSO) is a seed oil from a new mutant sunflower line characterized by increased levels of both oleic acid (>50%) and palmitic acid (>25%) and a high oxidative stability. In this study, its performance at frying temperature was compared with that of palm olein in thermoxidative assays (4 h, 180°C). Also, industrial discontinuous frying of almonds, peanuts, and sunflower seeds (200 kg of each product) was carried out to define both the performance of HOHPSO and the main changes undergone by the foods. The evaluation of polar compounds and their distribution in the main groups, i.e., polymers, oxidized monomers, and DAG, as well as changes in tocopherols and oxidative stability, demonstrated the excellent behavior of HOHPSO during thermoxidation and frying. The increase in polar compounds and the loss of tocopherols and stability were much lower for HOHPSO than for palm olein under identical heating conditions. Only 1.3% polar compounds were formed during industrial discontiuous frying for 4 h and the oil stability increased, probably due to the formation of antioxidant compounds. As for the foods, the FA composition of the surface oil was clearly different from that corresponding to the internal oil, the former denoting the presence of HOHPSO in high concentration, particularly in fried sunflower seeds. Changes in oil stability of the foods attributable to the frying process clearly demonstrate the interest in using a highly stable oil such as HOHPSO to protect the surface against oxidation during food storage.     

Comparison of the Frying Performance of High Oleic Oils Subjected to Discontinuous and Prolonged Thermal Treatment

Frying is a popular practice because of its unique sensory characteristics and low cost. The high temperature reached with this cooking method alters molecules present in the oil. The deterioration of the oil depends primarily on its chemical composition. The aim of this study was to evaluate the thermal stability of high oleic sunflower oil (HOSO), sunflower oil (SO) and mixed oil (MIX) during deep frying of French fries. Octanoic acid and unsaturated fatty acid (UFA)/saturated fatty acid (SFA) ratio showed a good correlation with total polar compounds (TPC) for all frying samples analyzed. HOSO and MIX were characterized by reduced levels of thermal degradation, while SO resulted in the highest values of oxidation products (highest TPC values). SO was also the oil more retained by the food matrix, whereas MIX was the least absorbed. HOSO and MIX, having a high oleic acid content (77.58 and 59.92 %, respectively) and a low linoleic acid content (13.42 and 25.70 %, respectively), showed the best characteristics for the frying process.     

Sunflower oil used for frying: Combination of column,gas and high-performance size-exclusion chromatography for its evaluation

The alterations of a sunflower oil were evaluated by column, gas and high-performance size-exclusion chromatography after being used for deep-fat frying fifteen repeated and discontinuous times. Polar compounds increased significantly (6.2 ± 0.3% to 18.7 ± 0.8% in oil). Linoleic acid decreased (53.8 ± 0.2 to 48.1 ± 0.8 mg/100 mg oil) while oleic acid remained unaltered after 15 fryings. Saturated fatty acids such as palmitic and stearic, also remained unaltered. Triglyceride polymers (0.1 ± 0.0 to 2.4 ± 0.2 mg/100 mg oil), triglyceride dimers (1.0 ± 0.2 to 6.7 ± 0.3 mg/100 mg oil) and oxidized triglycerides (3.4 ± 0.2 to 7.6 ± 0.3 mg/100 mg oil) increased significantly in the oil used 15 times to fry potatoes. These thermoxidative compounds correlated well with the number of fryings (r=0.9864, r=0.9535 and r=0.9758, respectively). Diglyceride compounds remained unaltered, while free fatty acids increased from 0.4 ± 0.0 to 0.6 ± 0.0 mg/100 mg oil. Both of these, which are characteristic of hydrolytic alteration, did not correlate significantly (r=0.5985 and r=0.4261, respectively) with the number of fryings. These data suggest that a thermoxidative process, rather than a hydrolytic one, took place in this study.     

Formation of 4‐Hydroxy‐2‐Trans‐Nonenal,a Toxic Aldehyde,in Thermally Treated Olive and Sunflower Oils

4‐Hydroxy‐2‐trans‐nonenal (HNE) is a toxic aldehyde produced mostly in oils containing polyunsaturated fatty acid due to heat‐induced lipid peroxidation. The present study examined the effects of the heating time, the degree of unsaturation, and the antioxidant potential on the formation of HNE in two light olive oils (LOO) and two sunflower oils (one high oleic and one regular) at frying temperature. HNE concentrations in these oil samples heated for 0, 1, 3, and 5 hours at 185 °C were measured using high‐performance liquid chromatography. The fatty‐acid distribution and the antioxidant capacity of these four oils were also analyzed. The results showed that all oils had very low HNE concentrations (<0.5 μg g^?1 oil) before heating. After 5 hours of heating at 185 °C, HNE concentrations were increased to 17.98, 25.00, 12.51, and 40.00 μg g^?1 in the two LOO, high‐oleic sunflower oil (HOSO), and regular sunflower oil (RSO), respectively. Extending the heating time increased HNE formation in all oils tested. It is related to their fatty‐acid distributions and antioxidant capacities. RSO, which contained high levels of linoleic acid (59.60%), a precursor for HNE, was more susceptible to degradation and HNE formation than HOSO and LOO, which contained only 6–8% linoleic acid.     

Effect of fatty acid composition of oils on flavor and stability of fried foods

Effects of fatty acid composition of frying oils on intensities of fried-food flavor and off-flavors in potato chips and french-fried potatoes were determined. Commercially processed cottonseed oil (CSO) and high-oleic sunflower oil (HOSUN) were blended to produce oils with 12 to 55% linoleic acid and 16 to 78% oleic acid. Analytical sensory panels evaluated french-fried potatoes and pilot plant-processed potato chips. Initially, both foods prepared in CSO (16% oleic/55% linoleic acid) had the highest intensities of fried-food flavor; however, this positive flavor decreased with decreasing levels of linoleic acid. 2,4-Decadienal in potato chips also decreased with decreasing linoleic acid in the oils. Frying oil stability, measured by total polar compounds (TPC), and oxidative stability of potato chips, measured by volatile compounds, showed that HOSUN (78% oleic acid) produced the lowest levels of TPC and the lowest levels of hexanal and pentanal, indicating greater frying oil stability and oxidative stability of the food. However, fresh potato chips fried in HOSUN had the lowest intensities of fried-food flavor and lowest overall flavor quality. Fried-food flavor intensity was the best indicator of overall flavor quality in fresh potato chips. Volatile compounds, TPC, and oxidative stability index directly varied with increasing oleic acid, and were therefore not directly indicative of flavor quality. No oil analysis predicted flavor stability of aged potato chips. Compositions of 16 to 42% oleic acid and 37 to 55% linoleic acid produced fresh fried-food with moderate fried food flavor intensity, good overall flavor quality, and low to moderate TPC levels (chips only). However, in aged food or food fried in deteriorated oil, compositions of 42 to 63% oleic and 23 to 37% linoleic provided the best flavor stability.     

Characteristics of tea seed oil in comparison with sunflower and olive oils and its effect as a natural antioxidant

A comparison of iodine values showed that the degree of saturation of tea seed oil (Lahjan variety) was intermediate between the oils of sunflowerseed (Fars variety) and olive (Gilezeytoon variety), and the saponification values of these three oils were similar. Tea seed oil consisted of 56% oleic acid (C18∶1), 22% linoleic acid (C18∶2), 0.3% linolenic acid (C18∶3), and therefore, on the basis of oleic acid, occupied a place between sunflower and olive oil. In studies at 63°C, the shelf life of tea seed oil was higher than that of sunflower oil and similar to olive oil. Tea seed oil was found to have a natural antioxidant effect, and it enhanced the shelf life of sunflower oil at a 5% level. In this study, tea seed oil was found to be a stable oil, to have suitable nutritional properties (high-oleic, medium-linoleic, and lowlinolenic acid contents), and to be useful in human foods.     

Thermoxidative stability of triacylglycerols from mutant sunflower seeds

Thermoxidative stability was evaluated in triaclyglycerols (TAG) from the oils of the mutant sunflower lines CAS-3, CAS-4, and CAS-8 (with a high percentage of stearic acid), CAS-5 (with a high percentage of palmitic acid), all from standard highlinoleic genetic backgrounds, and the mutant sunflower line CAS-12 (with a high percentage of palmitic acid), from a high-oleic genetic background. These oils contained unusually high contents of TAG molecular species with one or two saturated fatty acids at the sn-1,3 positions. Purified total TAG devoid of tocopherols were subjected to controlled thermoxidative treatment at 180°C. Polymerized TAG were determined at 2-h intervals for 10 h. After this time, total polar compounds, oxidized TAG monomers, TAG dimers, and TAG oligomers were determined. TAG from highly saturated sunflower oils with levels of linoleic acid similar to those found in conventional sunflower oils (40–50%) showed enhanced thermal stability. In these TAG, the amount of polar compounds formed during the thermoxidative treatment was similar to that formed in the high oleic acid line. Excellent results were obtained for the TAG of the CAS-12 oil, which had the highest thermal stability, producing half the amount of polar compounds as the conventional line and less than two-thirds that of the high-oleic line.     

Virgin sunflower oil

Sunflower oil is the second most important virgin oil in Europe but, from the nutritional point of view, the assessment of this oil has become increasingly poorer over the last few years because of the high amount of linoleic acid in traditional sunflower seeds. Today sunflower oil with a high oleic acid content is coming more into the focus of interest since the fatty acid composition is more comparable to rapeseed and olive oil. Another important aspect is that the high content of oleic acid results in a high oxidative stability, making this oil interesting for a wide range of applications. A special challenge is the production of high‐quality tasty virgin sunflower oil because, in contrast to other raw materials, about 30% of sunflower seeds consist of hulls that are covered by waxes. During oil processing these waxes are co‐extracted with the oil, resulting in undesired turbidity of the oil on storage. Pressing of the raw material is done in a screw press or expeller and results in residue fat contents between 7 and 15% depending on the pressing conditions. We discuss two possibilities to avoid or to remove waxes by dehulling of the seeds or winterisation of the resulting oil. Dehulling is carried out by an impact dehuller with removal of the hulls by airflow and gravity. Removal of hulls before pressing improves the sensory quality of the oil because it results in products with a mild sunflower seed‐like nutty taste, while oils from whole seeds often have a woody and bitter taste. In addition, the development of heat during pressing is reduced if dehulled seeds are used for oil production. Conventional sunflower seeds are processed mainly in big oil mills, whereas in small and medium‐sized facilities organic raw material is in use.     

Utilization of high‐oleic rapeseed oil for deep‐fat frying of French fries compared to other commonly used edible oils

Changes in chemical, physical and sensory parameters of high‐oleic rapeseed oil (HORO) (NATREON?) during 72 h of deep‐fat frying of potatoes were compared with those of commonly used frying oils, palm olein (PO), high‐oleic sunflower oil (HOSO) and partially hydrogenated rapeseed oil (PHRO). In addition to the sensory evaluation of the oils and the potatoes, the content of polar compounds, oligomer triacylglycerols and free fatty acids, the oxidative stability by Rancimat, the smoke point and the anisidine value were determined. French fries obtained with HORO, PO and HOSO were still suitable for human consumption after 66 h of deep‐fat frying, while French fries fried in PHRO were inedible after 30 h. During the frying period, none of the oils exceeded the limit for the amount of polar compounds, oligomer triacylglycerols and free fatty acids recommended by the German Society of Fat Science (DGF) as criteria for rejection of used frying oils. After 72 h, the smoke point of all oils was below 150 °C, and the amount of tocopherols was reduced to 5 mg/100 g for PHRO and 15 mg/100 g for HORO and HOSO. Remarkable was the decrease of the oxidative stability of HOSO measured by Rancimat. During frying, the oxidative stability of this oil was reduced from 32 h for the fresh oil to below 1 h after 72 h of frying. Only HORO showed still an oxidative stability of more than 2 h. From the results, it can be concluded that the use of HORO for deep‐fat frying is comparable to other commonly used oils.     

Polar content vs. TAG oligomer content in the frying-life assessment of monounsaturated and polyunsaturated oils used in deep-frying

The frying-lives of olive oil (OO), sunflower oil (SO), and a blend of these oils (BO) were assessed and compared by measuring the polar content (PC) and the TAG oligomer content (TOC) in the oils. Oil was replenished with fresh oil every 10 uses in all three oils. Changes in the PC and TOC in relation to the number of frying uses were fitted to different curvilinear models. The power model yields the highest R ² value in the three oils. The 25% PC was surpassed after 32.2 fryings [95% confidence interval (95% Cl) 29.1–36.8] in the OO, 22.5 (95% Cl, 21.0–24.6) fryings in the SO, and 27.5 (95% Cl, 25.5–30.1) fryings for BO. However, according to the 10% TOC cutoff point, OO should be discarded after 25.0 (95% Cl, 22.8–28.7) fryings, SO after 15.0 (95% Cl, 14.8–15.4) fryings, and BO after 17.7 (95% Cl, 17.0–19.1) fryings. Nevertheless, changes in PC and TOC were different only between OO and SO (P<0.05 and P<0.02, respectively), indicating that OO performs better than SO, and that BO can be used as an alternative when both frying-life and price are under consideration. Present findings suggest the need to unify criteria in different countries for oil disposal because the 25% PC corresponds to a TOC higher than 10%.     

Pan-frying stability of NuSun oil,a mid-oleic sunflower oil

Pan-frying is a popular frying method at home and in many restaurants. Pan-frying stabilities of two frying oils with similar iodine values (IV)—mid-oleic sunflower oil (NuSun oil; IV=103.9) and a commercial canola oil (IV=103.4)—were compared. Each oil sample was heated as a thin film on a Teflon-coated frying pan at ∼180°C to a target end point of ≥20% polymer. High-performance size-exclusion chromatography analysis of the mid-oleic sunflower and canola oil samples indicated that the heated samples contained 20% polymer after approximately 18 and 22 min of heating, respectively. The food oil sensor values increased from zero to 19.9 for the canola sample and from zero to 19.8 for the mid-oleic sunflower sample after 24 min of heating. The apparent first-order degradation rate for the mid-oleic sunflower sample was 0.102±0.008 min⁻¹, whereas the rate for the canola sample was 0.092±0.010 min⁻¹. The acid value increased from approximately zero prior to heating to 1.3 for the canola sample and from zero to 1.0 for the mid-oleic sunflower sample after 24 min of heating. In addition, sensory and volatile analyses of the fried hash browns obtained from both oils indicated there were no significant differences between the two fried potato samples.     

Sunflower oil and its applications

Sunflower is one of the oldest oilseeds in the Americas. It is the state flower of Kansas State and constitutes a significant segment of oilseeds produced in the former Soviet Union Block. Sunflower is admired worldwide for its vibrant beauty and is an important source of food. Its oil is viewed as a healthy vegetable oil and its seeds contain a wide range of nutrients that are enjoyed as a tasty snack as well as nutritious ingredient in many foods, such as health bars, salad garnish and spreads similar to peanut butter. Sunflower is an important crop choice for US growers from the northern plains of Dakotas to Texas panhandle. The oil has very good taste and appearance. Today, there is the traditional sunflower oil, which is high in linoleic acid content that makes it excellent for both domestic and industrial use. The high linoleic acid content makes the oil unstable in industrial or institutional frying. Mid‐oleic sunflower, which contains higher oleic acid and lower level of linoleic acid than the garden variety sunflower oil is more suitable for industrial and institutional frying along with the applications such as salad oil and cooking oil. High oleic sunflower oil, that contains 80% or higher oleic acid and very low linoleic acid, is one of the most stable oils for all applications, including industrial and institutional frying, and also for industrial non‐food applications such as lubricant, as transformer oil and various other applications.     

Hydrolysis of used frying palm olein and sunflower oil catalyzed by porcine pancreatic lipase

The enzymatic hydrolysis of frying used vegetable oils with different degrees of alteration were measured using porcine pancreatic lipase (acylglycerol acylhydrolase EC 3.1.1.3). Successive frying of potatoes significantly increased the level of total polar lipid content in the palm olein from 9.3±0.1 mg/100 mg oil to 26.4±0.3 mg/100 mg oil after 90 fryings, and from 4.0±0.1 mg/100 mg oil to 27.7±0.3 mg/100 mg oil in sunflower oil after 60 fryings. Triacylglycerol polymers, triacylglycerol dimers, and oxidized triacylglycerols also increased 37-, 7.9-, and 7.5-times in palm olein, respectively, and 56-, 22-, and 4.7-times in sunflower oil, respectively. However, diacylglycerols and free fatty acid levels related to hydrolytic alteration did not increase with the number of fryings in both oils. The substrate concentration in the reactor was determined by calculating the molecular weight of each oil showing a different degree of alteration. We compared the methodology used by us and that used by other authors. The results show that the methods are reproducible and that the values obtained are in concordance with theoretical values. The kinetic parameters apparent Michaelis-Menten constant (K _M ^app ) and apparent maximum velocity of hydrolysis (V _max ^app ) were different in unused palm olein (5.1±0.7 and 166±7.6, respectively) than in sunflower oil (2.2±0.3 and 62±2.2, respectively). However, changes inK _M ^app andV _max ^app were not related to the degree of alteration of the oils.     

Improving the oxidative stability of polyunsaturated vegetable oils by blending with high-oleic sunflower oil

Mixing different proportions of high-oleic sunflower oil (HOSO) with polyunsaturated vegetable oils provides a simple method to prepare more stable edible oils with a wide range of desired fatty acid composition. Oxidative stability of soybean, canola and corn oils, blended with different proportions of HOSO to lower the respective levels of linolenate and linoleate, was evaluated at 60°C. Oxidation was determined by two methods: peroxide value and volatiles (hexanal and propanal) by static headspace capillary gas chromatography. Determination of hexanal and propanal in mixtures of vegetable oils provided a sensitive index of linoleate and linolenate oxidation, respectively. Our evaluations demonstrated that all-cis oil compositions of improved oxidative stability can be formulated by blening soybean, canola and corn oils with different proportions of HOSO. On the basis of peroxide values, a partially hydrogenated soybean oil containing 4.5% linolenate was more stable than the mixture of soybean oil and HOSO containing 4.5% linolenate. However, on the basis of volatile analysis, mixtures of soybean and HOSO containing 2.0 and 4.5% linolenate were equivalent or better in oxidative stability than the hydrogenated soybean oil. Mixtures of canola oil and HOSO containing 1 and 2% linolenate had the same or better oxidative stability than did the hydrogenated canola oil containing 1% linolenate. These studies suggest that we can obviate catalytic hydrogenation of linolenate-containing vegetable oils by blending with HOSO. Presented at the AOCS/JOCS joint meeting, Anaheim, CA, April 25–29, 1993.     

Effect of heat and frying on sunflower,oil stability

Sunflowers are one of the most important sources of vegetable oils in the world, second only to soybeans. Although in use throughout many parts of the world, sunflower seed are just now beginning to attact attention and use in the United States. Composition of the oil appears to be dependent on area of production. Sunflower oil from seed grown in northern US typically contains 70% linoleic acid. In contrast, oil from seed produced in the South generally contains 40–50% linoleic acid and is higher in mono-unsaturated fats. For most of the edible oil market, sunflower oil appears to have an advantage over most other vegetable oils. Lightly hydrogenated sunflower oil was compared with a cottonseed-corn oil mixture for frying potato chips. Organoleptic evaluation indicated that chips did not differ significantly. We also evaluated the useful life of various sunflower seed oils for deep-fat frying. Hydrogenated and unhydrogenated sunflower oils and a commercial shortening were used to deep-fry raw potatoes. A plot of the log of the Active Oxygen Method (AOM) values of the oils versus time gave a straight line, the slope of which reflects the oxidizability of the oil. Data indicated that lightly hydrogenated northern sunflower oil was much less prone to oxidation after abuse than the commercial shortening and was useful for a longer time. The southern oil deteriorated faster than the northern sunflower oil, but the two oils were processed differently. Thus, in recent work, care was taken to process both northern and southern grown sunflower seed under identical conditions. Frying studies indicated that oil from southern grown seed was more stable than that from northern seed as would be expected from their fatty acid composition.