Die Notwendigkeit,neue Qualitätsanforderungen für rohes Sojaöl einzuführen

Necessity for the Introduction of New Quality Requirements for Crude Soybean Oil Crude degummed soybean oils of good and inferior quality were refined in semi continuous scale and the refined oils were investigated with respect to colour and flavour stability. The results showed that the colour and flavour stability of the end product are dependent on oxidation characteristics, i. e. p-anisidine value, peroxide value and UV absorbence, and from iron and phosphorus content of the crude oil. Therefore, it is necessary, in addition to current quality requirements, that the maximum values of oxidation characteristics and iron content should be specified.     

Trace metal contents,chemical properties and oxidative stability of capelin and herring oils produced in norwegian plants

The iron and copper contents of 14 crude capelin oils, two herring oils and one blend produced in oil meal plants in northern Norway were determined by atomic absorption spectroscopy (AAS). Their oxidative stability, peroxide (PV), benzidine (BV) and iodine values (IV), free fatty acids (FFA) and tocopherol contents were also evaluated. The oxidative stability was found to be more dependent on the tocopherol content and BV of the crude oils than on their content of trace metals. Changes in iron, copper and nickel contents were determined by AAS after refining and hydrogenation of marine oils in two Norwegian hydrogenation plants. The content of trace metals in the oils and hydrogenated products decreased as a result of alkali refining and bleaching to the lower limits of detectability by the method used, and amounted to 0.01 (oils), 0.02 and <0.3 ppm for iron, copper and nickel respectively.     

The Antioxidant Activity and Oxidative Stability of Cold-Pressed Oils

In our study, we characterized the antioxidant activity and oxidative stability of cold-pressed macadamia, avocado, sesame, safflower, pumpkin, rose hip, Linola, flaxseed, walnut, hempseed, poppy, and milk thistle oils. The radical scavenging activity of the non-fractionated fresh oil, as well as the lipophilic and hydrophilic fractions of the oil was determined using a 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The fatty acid composition of the fresh and stored oils was analyzed by gas chromatography. The acid value, peroxide value, p-anisidine value and conjugated diene and triene contents in the fresh oils, as well as in those stored throughout the whole period of their shelf life, were measured by CEN ISO methods. The antioxidant activity of the oils expressed as Trolox equivalent antioxidant capacity (TEAC), ranged from 0.17 to 2.32 mM. The lipophilic fractions of the oils were characterized by much higher antioxidant activity than the hydrophilic ones. There were no significant changes in fatty acid composition and only slight changes in the oxidative stability parameters of the oils during their shelf life. Through the assessment of the relationship between antiradical activity and the oxidative stability of oils, it is proposed that a DPPH assay predicts the formation of oxidation products in cold-pressed oils—however, the correlations differ in fractionated and nonfractionated oils.     

Stability of a phenol‐enriched olive oil during storage

The use of an emulsifier to stabilize the phenolic compounds added in the preparation of an enriched olive oil was evaluated. Two emulsifiers, lecithin and monoglyceride, were studied. The results showed lecithin to be the most convenient, due to the increase in the value of the oxidative stability of the phenol‐enriched oils in relation to the enrichments prepared with monoglycerides. After that, the shelf life of the prepared oils was evaluated during a period of 256 days of storage at 25°C in the dark. Oil quality parameters, total phenolic content, bitterness index and oxidative stability were studied during the storage period. Additionally, the phenolic composition and antioxidant capacity (by using the ORAC assay) were evaluated at the end of the storage. The phenolic enrichment of the oils allowed the shelf life of the oils to be extended compared with the control (virgin olive oil without phenol addition), delaying the appearance of peroxides and improving their oxidative stability. In addition, the higher content of phenolic compounds in the oils at all stages of storage is desirable in order to increase the intake of these beneficial compounds. Practical applications : The preparation of phenol‐enriched olive oils with a higher phenolic content than the commercial virgin olive oils is of special interest to increase the ingestion of these healthy compounds the daily intake of which is limited due to the high caloric value of olive oil. There are two key points in the development of this product: (i) the dispersion and stabilization of the phenol extract in the oil matrix and (ii) the stability of the phenols in the prepared oils to guarantee the phenol concentration during their shelf life. It is important to study the use of emulsifiers to determine if they allow an improvement in the dispersion of the phenolic extract, and their stabilization in the final product. In addition, the emulsifiers could mask the bitter taste of the enriched oils, which is desirable to increase consumer acceptance of the enriched oil.     

Oxidative stability of black cumin (Nigella sativa L.), coriander (Coriandrum sativum L.) and niger (Guizotia abyssinica Cass.) crude seed oils upon stripping

Information on stability of edible oils is important for predicting the quality deterioration of the oil during storage and marketing. Stripping of crude oils removes most of non‐triacylglycerol components, including polar lipids and phenolics. Oxidative stability of black cumin (Nigella sativa L.), coriander (Coriandrum sativum L.) and niger (Guizotia abyssinica Cass.) crude and stripped seed oils was investigated and compared. The factors influencing the oxidative stability of different seed oils were also discussed. Oil samples were stored under accelerated oxidation conditions for 21 d. The progress of oxidation at 60 °C was followed by recording the ultraviolet absorptivity and measuring the formation of oxidative products (peroxide and p‐anisidine values). Inverse relationships were noted between peroxide values and oxidative stabilities and also between secondary oxidation products, measured by p‐anisidine value and stabilities at termination of the storage. Absorptivity at 232 nm and 270 nm increased gradually with the increase in time, due to the formation of conjugated dienes and polyenes. In general, oxidative stabilities of crude oils were stronger than their stripped counterparts and the order of oxidative stability was as follows: coriander > black cumin > niger seed. Levels of polar lipids in crude oils correlated with oxidative stability. Thus, the major factor that may contribute to the better oxidative stability of crude oils was the carry‐over of their polar lipids.     

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.     

Chemische Untersuchungen an Speiseölen unter besonderer Berücksichtigung polyensäurereicher Öle

Analysis of Edible Oils with Special Consideration of Oils Containing Polyunsaturated Fatty Acids 32 different edible oils including several oils containing unsaturated fatty acids were controlled with reference to quality and oxidation state by determination of acid content, saponification value, peroxide value, thiobarbituric acid value, volatile substances and smoke point before and after heating. Except for the fact that heating always causes a reduction of quality of oils, native olive oils and sunflower oils proved to be very susceptible for oxidation whereas refined “table” oils and corn oils showed higher stability.     

Flavor and oxidative stability of continuously hydrogenated soybean oils

Soybean oil was partially hydrogenated in a continuous system with copper and nickel catalysts. The hydrogenated products were evaluated for flavor and oxidative stability. Processing conditions were varied to produce oils of linolenate contents between 0.4 and 2.7%, as follows: oil flow, 0.6–2.2 liters/hr; reaction temperature, 180–220 C; hydrogen pressure, 100–525 psig, and catalyst concentration, 0.5–1% copper catalyst or 0.1% nickel catalyst.Trans unsaturation varied from 8 to 20% with copper catalyst and from 15.0 to 27% with nickel catalyst. Linolenate selectivity was 9 with copper catalyst and 2 with nickel catalyst. Flavor evaluation of finished oils containing 0.01% citric acid (CA), appraised initially and after accelerated storage at 60 C, showed no significant difference between hydrogenated oils and nonhydrogenated oil. However, peroxide values and oxidative stability showed that hydrogenated oils were more stable than the unhydrogenated oil. CA+TBHQ (tertiary butylhydroquinone) significantly improved the oxidative stability of test oils over oils with CA only, but flavor scores showed no improvement. Dimethylpolysiloxane (MS) had no effect on either flavor or oxidative stability of the oils.     

Polyphenols in olive oils

The levels of total polyphenols and o-diphenols were determined in virgin oils and in chloroform/methanol-extracted oils. The solventextracted oils were richer in polyphenols than the virgin oils. High polyphenol content was associated with a high resistance to oxidation of the oils. A linear relationship was found between polyphenol content and the oxidative stability of the virgin oils during storage at 60 C. After removal of the polyphenols, the oxidative stability of the oils decreased considerably and seemed to depend on polyunsaturated fatty acid concentration.     

Oxidative stability of flax and hemp oils

Oxidative stability of flax and hemp oils, and of flax and hemp oils stripped of their minor components, was evaluated in the dark at 60°C and under fluorescent light at 27°C. Several analytical methods were used to assess the oxidative stability of oils. Oil extracts were also investigated for their scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and for their total phenolic contents. The results indicate that bioactive constituents of these edible oils play a major role in their oxidative stability. However, the FA composition of the oils and their total content of tocopherols as well as the type of pigments present contribute to their stability. Nonstripped flax and hemp oils were more stable than their corresponding stripped counterparts. Furthermore, nonstripped hemp oil had a higher oxidative stability than nonstripped flax oil as evidenced by scavenging of DPPH radical and consideration of total phenolic contents.     

Veränderungen der Fette unter Fritierbedingungen und deren analytische Erfassung Beurteilung des Gebrauchswertes und Analytik von Fritierfetten I

Alterations in Fats Under Frying Conditions and Their Analytical Detection: Evaluation of the Quality of Frying Fats and Their Analysis The quality of a frying fat at a certain stage of use depends on its composition, its freshness, and the frying conditions. The frying stability, i. e. the length of time a fat can be heated in the fryer till the content of petroleum ether insoluble oxidized fatty acids reaches a level of 1%, is proportional to the degree of saturation of the fat, and inversely proportional to its specific surface in the fryer and its reversion period. Frying stability can be increased considerably by excluding atmospheric oxygen. Thus, under suitable frying conditions even highly unsaturated fats, such as peanut oil, sunflower oil, and soybean oil, can be used without an increase in the content of oxidized fatty acids above a permitted level. In the choice of fats one should prefer those having lower UV-absorbance and higher SWIFT stability. In order to define the degree of oxidation of used frying fats, it is recommended to determine the content of oxidized fatty acids according to DGF-Standard Method C-III 3 (68). Moreover, acid value, smoke point and UV-absorbance provide valuable information regarding the degree of oxidative changes. A rather loose relationship exists between the saponification colour number and the content of oxidized fatty acids.     

Oxidative stability of structured lipids produced from borage (<Emphasis Type="Italic">Borago officinalis</Emphasis> L.) and evening primrose (<Emphasis Type="Italic">Oenothera biennis</Emphasis> L.) oils with docosahexaenoic acid

This study utilized γ-linolenic acid (18∶3n−6; GLA)-rich borage oil (BO) and evening primrose oil (EPO) for the synthesis of structured lipids (SL) and compared the oxidative stability of the products with those of unmodified BO and EPO as controls. Immobilized Novozym 435 lipase from Candida antarctica was used as the biocatalyst for SL production. BO or EPO eas enzymatically modified with docosahexaenoic acid (22∶6n−3; DHA), as the acyl donor, to produce SI. The SI were characterized and their oxidative stabilities evaluated. Among the oils examined, SL gave rise to higher quantities (P≤0.05) of conjugated dienes, TBARS, and headspace volatiles as compared to their unmodified counterparts. Results indicated that modified oils were less stable than their unmodified counterparts. The double bond index (DBI) and methylene bridge index (MBI) of oils decreased (P<0.05) during oxidation in the more unsaturated oils. An attempt was made to correlate various parameters of oxidation with DBI and MBI of oils; correlation coefficients (−r) were within the range of 0.574–0.973. This suggests that indicators such as DBI and MBI can reflect oxidative stability of oils.     

Long term storage of soybean and cottonseed salad oils

Commercially prepared and packaged soybean and cottonseed salad oils from several different processors were evaluated periodically during storage for 12 months. Partially hydrogenated and winterized soybean oils, as well as unhydrogenated soybean salad oils, were stored in bottles and cans at 78 and 100 F. Control samples of all oils were held at 0 F during the entire test. Some lots in bottles and cans were packaged under nitrogen to improve storage stability. Agreement was good between organoleptic and oxidative evaluation of aged oils. After 26 weeks of storage at 100 F, the flavor of partially hydrogenated-winterized oils packaged under nitrogen showed a minimum loss. These same oils did not exhibit much, if any, reduction in their oxidative stability as indicated by storage peroxide values (active oxygen method). Soybean oil not protected with nitrogen demonstrated progressive flavor deterioration at 100 F. After 10 weeks of storage, the deterioration became marked and the flavor score was below 5. From limited observations, bottled oils appear to have a better stability than oils packaged in screw-cap tin cans. Hydrogenated oils packaged under nitrogen in cans had good oxidative stability, but some lowering of the flavor score was observed. Nonhydrogenated soybean oils packaged in tin cans not under nitrogen exhibited the most rapid flavor deterioration of all lots of oil investigated. Presented in part at the AOCS meeting, New York, October 1968 ARS, USDA     

Effect of natural antioxidants in virgin olive oil on oxidative stability of refined,bleached, and deodorized olive oil

The factors influencing the oxidative stability of different commercial olive oils were evaluated. Comparisons were made of (i) the oxidative stability of commercial olive oils with that of a refined, bleached, and deodorized (RBD) olive oil, and (ii) the antioxidant activity of a mixture of phenolic compounds extracted from virgin olive oil with that of pure compounds andα-tocopherol added to RBD olive oil. The progress of oxidation at 60°C was followed by measuring both the formation (peroxide value, PV) and the decomposition (hexanal and volatiles) of hydroperoxides. The trends in antioxidant activity were different according to whether PV or hexanal were measured. Although the virgin olive oils contained higher levels of phenolic compounds than did the refined and RBD oils, their oxidative stability was significantly decreased by their high initial PV. Phenolic compounds extracted from virgin olive oils increased the oxidative stability of RBD olive oil. On the basis of PV, the phenol extract had the best antioxidant activity at 50 ppm, as gallic acid equivalents, but on the basis of hexanal formation, better antioxidant activity was observed at 100 and 200 ppm.α-Tocopherol behaved as a prooxidant at high concentrations (>250 ppm) on the basis of PV, but was more effective than the other antioxidants in inhibiting hexanal formation in RBD olive oil.o-Diphenols (caffeic acid) and, to a lesser extent, substitutedo-diphenols (ferulic and vanillic acids), showed better antioxidant activity than monophenols (p- ando-coumaric), based on both PV and hexanal formation. This study emphasizes the need to measure at least two oxidation parameters to better evaluate antioxidants and the oxidative stability of olive oils. The antioxidant effectiveness of phenolic compounds in virgin olive oils can be significantly diminished in oils if their initial PV are too high.     

Quality differences between pre‐pressed and solvent extracted rapeseed oil

Most seed oils are obtained by pre‐pressing the crushed seeds followed by solvent extraction of oil from the press cake. The prepressed oil will contain no solvent residues, and is moreover expected to contain more nutritionally valuable compounds, which can in turn enhance the oxidative stability of the oil. However, reports on differences between extracted and pressed oils are scarce. Therefore, in this study, for a case study on rapeseed oil, the composition and quality were systematically compared between pre‐pressed and solvent extracted oil. In the extracted oil, solvent residues and a clear sensory difference were detected, which disappeared almost completely during refining. The crude oils had a high content in free fatty acids and in primary and secondary oxidation products, which were higher in the extracted than in the pressed oil. However, surprisingly, also the content of minor compounds was slightly higher in the extracted oil than in the pressed oil. This can be explained by a selective extraction of those compounds into the solvent. During refining, a difference between pressed and extracted oils still existed but was less pronounced. The slight difference in antioxidants content might explain the higher oxidative stability of extracted over pressed oils. Practical applications : Traditionally, high yields of vegetable oils are obtained by pre‐pressing the seeds, followed by solvent extraction of the residual oil from the press cake. The solvent extraction leads to higher oil yields, but is expected to affect the composition and quality of the oil, and has moreover negative environmental impacts. In this study, the solvent extracted oil contained slightly higher levels of tocopherols and phytosterols, and had slightly higher oxidative stability, which are desirable quality aspects. In contrast, the solvent extracted oil contained also higher levels of undesirable phospholipids, as well as solvent residues, which were, however, removed during degumming and deodorization, respectively. These results suggest that the final quality of refined pre‐pressed and solvent extracted oils is comparable from nutritional and safety point of view. A choice for pressing instead of solvent extraction will, therefore, rather be driven by sustainability concerns than by nutritional aspects.     

Increasing gamma‐ and delta‐tocopherols in oils improves oxidative stability

Over the past two decades, plant geneticists have revolutionized how fatty acid compositions of vegetable oils are optimized to improve oxidative stability and functionality. Now, the expertise of plant geneticists is reaching beyond altering fatty acids to changing other oil components such as tocopherols. Basic lipid research on optimizing tocopherol profiles and ratios in vegetable oils is providing information for geneticists to breed the next generation of oxidatively stable vegetable oils. This review will discuss three studies; first, a basic study to determine the oxidative stability provided by the addition of pure gamma and delta tocopherols to oils treated to remove natural tocopherols; second, a practical study to evaluate the oxidative stability of mid‐oleic sunflower oil from seeds modified by plant breeding to contain high amounts of γ‐ and δ‐tocopherols; and third, a frying test to determine the effects of gamma tocopherol addition.     

Oxidative stability of soybean oil fatty acid methyl esters by oil stability index (OSI)

Biodiesel, an alternative diesel fuel derived from transesterification of vegetable oils or animal fats, is composed of saturated and unsaturated long-chain FA alkyl esters. During long-term storage, oxidation caused by contact with air (autoxidation) presents a legitimate concern with respect to monitoring and maintaining fuel quality. Extensive oxidative degradation may compromise quality by adversely affecting kinematic viscosity, acid value, or PV. This work examines the oil stability index (OSI) as a parameter for monitoring the oxidative stability of soybean oil FAME (SME). SME samples from five separate sources and with varying storage and handling histories were analyzed for OSI at 60°C using an oxidative stability instrument. Results showed that OSI may be used to measure relative oxidative stability of SME samples as well as to differentiate between samples from different producers. Although addition of α-tocopherol or TBHQ increased OSI, responses to these antioxidants varied with respect to SME sample. Variations in response to added antioxidant were attributed to aging and other effects that may have caused oxidative degradation in samples prior to acquisition for this study. Results showed that OSI was more sensitive than iodine value in detecting the effects of oxidative degradation in its early stages when monitoring SME during storage.     

Some physical properties and oxidative stability of biodiesel produced from oil seed crops

Biodiesel is a cleaner burning fuel than petrodiesel and a suitable replacement in diesel engine. It is produced from renewable sources such as vegetable oils or animal fats. Biodiesel fuel was prepared from castor (CSO), palm kernel (PKO) and groundnut (GNO) oils through alkali transesterification reaction. The biodiesel produced was characterized as alternative diesel fuel. Fuel properties such as specific gravity, viscosity, calorific (combustion) value, The CSO, PKO and GNO were measured to evaluate the storage/oxidative stability of the oils to compare them with commercial petrodiesel. The biodiesel produced had good fuel properties with respect to ASTM D 6751 and EN 14214 specification standards, except that the kinematic viscosity of castor oil biodiesel was too low. The viscosity of castor oil biodiesel at different temperatures was in the range of 4.12–7.21 mm²/s. However, promising results which conformed to the above specification standards were realized when castor oil biodiesel was blended with commercial petrodiesel. At 28 °C the specific gravity recorded for CSO, PKO and GNO biodiesel was higher than the values obtained for petrodiesel. Commercial petrodiesel had the highest oxidative stability than biodiesel produced from CSO, PKO and GNO oils.     

The effect of oxygen concentration on oxidative deterioration in heated high-oleic safflower oil

High-oleic safflower oil was heated at 180°C in atmospheres with four levels of oxygen concentration (2, 4, 10, and 20%) modified with nitrogen gas, to assess the effects of atmospheric oxygen concentration on the oxidative deterioration of deep-frying oils. Acid value, carbonyl value, polar materials, linoleic acid, tocopherol contents, and oxidative stability were measured to evaluate the quality of heated oils. These values were found to be correlated with both heating time and oxygen concentration. Acid and carbonyl values and polar material content of oils heated at oxygen concentrations of 2 and 4% were lower than those at 10 or 20%. On the other hand, linoleic acid and tocopherols were hardly reduced in oils after heating for 30 h at 2% O₂, whereas they were decomposed according to the oxygen concentration and heating time. Oxidative stability was well maintained in oils heated at 2 and 4% O₂. These results suggest that the oxidative deterioration of heated higholeic safflower oil depends on oxygen concentration.     

Oxidative stability of stripped and nonstripped borage and evening primrose oils and their emulsions in water

Oxidative stability of stripped and nonstripped borage and evening primrose oils and their emulsions in water was evaluated. The results indicated that column chromatographic techniques provide an effective means for stripping vegetable oils of their minor components. However, some minor components may be retained in the stripped oils. The minor components in borage and evening primrose oils significantly (P<0.05) influenced their oxidative stability in the dark. In contrast, the behavior of endogenous antioxidants in borage and evening primrose oil-in-water emulsions, according to the “polar paradox” theory, was difficult to evaluate. Correlations existed between peroxide value (PV) and conjugated dienes (CD) (P<0.05) as well as 2-thiobarbituric acid-reactive substances (TBARS) and hexanal content (P<0.01) for most oils and emulsion systems. Therefore, CD and TBARS may generally be used to assess the oxidative stability of borage and evening primrose oils and their oil-in-water emulsions in addition to or in place of PV and headspace volatiles, respectively.