Analysis of carotenoids and vitamin E in selected oilseeds,press cakes and oils

Carotenoids and vitamin E in oils from the market – 6 rapeseed and 6 sunflower oils, half of each cold pressed and refined – and in the oils of rape, sunflower, flax and safflower as well as the respective seeds and press cakes from a local oil mill were quantified by HPLC. Furthermore, a photometric determination of carotenoid content was tested and checked against the chromatographic method. In the cold pressed oils minor amounts of xanthophylls (all‐E)‐lutein and (all‐E)‐zeaxanthin were determined. With exception of traces of (all‐E)‐β‐carotene in cold‐pressed rapeseed oil this provitamin A active compound did not occur. Cold pressed rapeseed oils contained 0.5–1.5 mg total carotenoids/100 g which was manifold the content of the further oils. Vitamin E was found in all vegetable oils at plant‐typic tocopherol patterns. The photometric determination of carotenoids resulted in significantly higher concentrations compared to the HPLC. This overestimation bases on the carotenoid pattern which was validated by comparison with known high‐carotenoid materials, i.e. maize flour with an abundant amount of xanthophylls and carrots with an abundant amount of carotenes.     

Oxidative Stability and Changes in Chemical Composition of Extra Virgin Olive Oils After Short‐Term Deep‐Frying of French Fries

We aimed at investigating oxidative stability and changes in fatty acid and tocopherol composition of extra virgin olive oil (EVOO) in comparison with refined seed oils during short‐term deep‐frying of French fries, and changes in the composition of the French fries deep‐fried in EVOO. EVOO samples from Spain, Brazil, and Portugal, and refined seed oils of soybean and sunflower were studied. Oil samples were used for deep‐frying of French fries at 180 °C, for up to 75 min of successive frying. Tocopherol and fatty acid composition were determined in fresh and spent vegetable oils. Tocopherol, fatty acid, and volatile composition (by SPME–GC–MS) were also determined in French fries deep‐fried in EVOO. Oil oxidation was monitored by peroxide, acid, and p‐anisidine values, and by Rancimat after deep‐frying. Differential scanning calorimetry (DSC) analysis was used as a proxy of the quality of the spent oils. EVOOs presented the lowest degree of oleic and linoleic acids losses, low formation of free fatty acids and carbonyl compounds, and were highly stable after deep‐frying. In addition, oleic acid, tocopherols, and flavor compounds were transferred from EVOO into the French fries. In conclusion, EVOOs were more stable than refined seed oils during short‐term deep‐frying of French fries and also contributed to enhance the nutritional value, and possibly improve the flavor, of the fries prepared in EVOO.     

Sensory and Physico‐Chemical Properties of Cold Press‐Produced Tomato (Lycopersicon esculentum L.) Seed Oils

In this study, roasted and unroasted (control) tomato seeds were cold pressed and the seeds, oils, and seed presscakes (meals) were analyzed. Some physicochemical properties, total phenolic content and antioxidant capacity, thermal properties, mineral contents, fatty acids, sterols and tocopherols compositions, volatile compounds and sensory evaluation of the tomato seed oils were determined. The tomato seeds contained 3.3 % of ash, 17.3 % of oil and 27.2 % of protein. The cold press oil recovery rate was 7.2 and 10.28 % for control and roasted seeds, respectively. There were eight sensory terms defining the oils together with 34 different aromatic compounds quantified. The volatile compounds furfural, hexanal, benzaldehyde and 2‐isobutylthiazole were found with the highest frequency in the samples. Roasted, green and tomato were defined as characteristic sensory terms for tomato seeds oils. Fifteen different minerals, melting and crystallization temperatures and enthalpies of the oil samples were also quantified. This study provides important data for the tomato seed oils, and proves that pre‐roasted tomato seed oils are high quality, nutritious and aromatics oils with higher levels of consumer acceptability.     

The Contents of Lignans in Sesame Seeds and Commercial Sesame Oils of China

In this study, the concentrations of three lignans in 100 sesame seeds and 56 sesame oils were determined using a newly developed method based on high‐performance liquid chromatography coupled with a UV/Vis detector. Total lignan contents in sesame seed and oil samples ranged from 2.52 to 12.76 and 3.38 to 11.53 mg/g, respectively. Black sesame seeds showed higher sesamin content (range 1.98–9.41 mg/g, mean 4.34 mg/g) and sesamolin content (range 1.06–3.35 mg/g, mean 1.92 mg/g) than the other three varieties of sesame seeds. Black sesame oils had higher contents of lignans than the white sesame oils, although remarkable differences were not observed. Hot pressed and small mill sesame oils expressed higher contents of sesamol, sesamin, and total lignans than the cold pressed and refined sesame oils. The results revealed that there is extensive variability in lignan concentration in sesame oils and seeds.     

Sensory evaluation of the odour of a sunflower oil emulsion throughout oxidation

Oxidation of unsaturated fatty acids is responsible for off‐flavours, often described as rancid flavours. This study was aimed at describing the evolution of the odour of a sunflower oil‐in‐water emulsion during oxidation at 50 °C in the dark. Appearance of an odour and occurrence of oxidation were first tested for at short‐time aging (0–4 h) by the triangle test and measurements of oxygen consumption, respectively. The odour of the emulsion oxidised for up to 240 h was then characterised by sensory profile, while volatiles issued from lipid oxidation were analysed in the headspace by SPME. From 1 h of aging, while oxygen consumption remained weak, a significant change of the odour was detected by the panel. Up to 21 volatile compounds were identified in the headspace of long‐time‐oxidised emulsions. Beyond the rancid attribute, seven attributes were chosen to describe the odour of oxidised emulsions, four of which referring to solutions of a single volatile oxidation compound. The contribution of the fresh oil attribute, initially dominant, was progressively overtaken from 6 to 24 h of aging by the deep‐fried attribute, which later declined in favour of the painty attribute, predominant after 100 h. Evolution of intensity scores and contribution to odour profiles of attributes could not be easily related to one reference volatile compound or another, confirming the complex relationship between the generated volatile compounds and the perceived odour.     

What we know and what we should know about virgin oils – a general introduction

On international scale the Codex Alimentarius Standard for Named Vegetable Oils differentiates between virgin oils and cold‐pressed oils, while in Germany virgin, non‐refined and refined oils are available. Here cold‐pressed is an additional quality feature. The paper explains and comments the various definitions for vegetable oils other than olive oil obtained by mechanical extraction only, because they are partly contradictory. Resulting from gentle processing virgin oils are often appreciated by the consumers as the better oils. The answer of the present paper to the question which type of oil is better is that there is no better or worse oil, but only a better or worse suitability of an oil for application in food processing or the kitchen. Finally, the paper picks up the upcoming debate on the potential ’?new' contaminant, 3‐MCPD‐fatty acid esters, which were found in refined oils.     

Chemical and Sensory Characteristics of Products Fried in High-Oleic,Low-Linolenic Rapeseed Oil

The effects of frying Berlin doughnuts and potato crisps in high-oleic, low-linolenic (HOLL) rapeseed oil were compared to other commonly used oils (i.e., palm olein, high-oleic sunflower oil, or partially hydrogenated oils). The chemical parameters characterizing the oxidative state of the products fried in HOLL were comparable to products being fried in other commonly used oils. The sensory characteristics of potato crisps fried in HOLL rapeseed oil were satisfactory and comparable to products fried in the other oils. Potato crisps were stable under nitrogen atmosphere for 20 weeks as measured by sensory quality scores. However, a storage time of 16 weeks was achieved for products stored under normal atmosphere. The suitability of HOLL rapeseed oil to improve the storage stability of Berlin doughnuts was limited. The sensory quality decreased during storage due to the development of abnormal taste and smell. Changes in the sensory quality were comparable to the results of the partially hydrogenated oils but worse for products fried in palm olein. Nevertheless, HOLL was a good alternative to partially hydrogenated oils as a frying medium.     

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.     

Sterinanalytik zum Nachweis eines Zusatzes von Sonnenblumenöl zu Safloröl

Determination of Sunflower Oil in Safflower Oil by Sterol Analysis Hitherto an addition of sunflower oil to safflower oil is hardly detectable, because fatty acid and tocopherol distribution and other chemical features are very similar. The knowledge of the described sterol distribution permits the detection of an addition of 5% sunflower oil to cold pressed safflower oil resp. 10% sunflower oil to crude and refined safflower oils by use of discriminant analysis.     

Oxidative stability of diacylglycerol oil and butter blends containing diacylglycerols

Diacylglycerol (DAG) oils produced from sunflower oil and traditional sunflower oil were stored for 20 wk at 38 °C, and their oxidative stability was measured. Moreover, two butter blends were produced containing 40 wt‐% DAG oil made from sunflower oil or rapeseed oil, respectively, as well as two control butter blends with sunflower oil or rapeseed oil. Their oxidative stability during storage at 5 °C for up to 12 wk was examined by similar means as for the pure oils. The storage study of the oils indicated that the DAG oil was oxidatively less stable as compared to sunflower oil, but that they had similar sensory quality. Storage of the butter blends revealed that blends with the two types of rapeseed oil (triacylglycerol (TAG) or DAG oil) were oxidatively more stable than the blends containing oils from sunflower. There was no unambiguous indication of DAG butter blends having a different stability than their respective control TAG blends. However, they had a significantly less salty and buttery flavour, which was ascribed to a much smaller water droplet size causing a delayed sensory perception in the mouth. The butter blend with DAG oil from rapeseed had a very neutral flavour. On the contrary, the butter blend with DAG oil from sunflower had a more rancid aroma and flavour than its control blend with sunflower oil.     

The DGF Rapeseed Oil Award – A tool to improve the quality of virgin edible rapeseed oil

Virgin cold pressed rapeseed oils are becoming more popular in Germany. They are characterized by their specific taste and smell which resembles asparagus, cabbage or fresh, green vegetables in contrast to the refined oils. The quality of virgin rapeseed oils on the German market is very heterogeneous, resulting in a problem for the consumer to choose an oil with a pleasant taste and smell. The German Society for Fat Science (DGF) created in 2006 the DGF Rapeseed Oil Award for virgin rapeseed oils of excellent flavour in order to highlight good products and to bring the sensory quality of virgin rapeseed oil more into the focus of the producers. The paper describes the reasons, procedure and the performance of the DGF Rapeseed Oil Award and discusses the question whether the medal is suitable to improve the quality of the oils in the market and to thereby strengthen the confidence of the consumer in the product. Additionally the results of the years 2006 and 2007 are shown.     

Aroma‐Relevant Volatile Compounds as Markers for the Sensory Quality of Argan Oil

The aim of the present work is to identify and characterize the most important aroma active compounds of argan oil from unroasted and roasted argan almonds as well as roasted almonds obtained from goat‐digested fruits by dynamic headspace GC and GC‐olfactometry with aroma dilution analysis to classify samples from the market according to their processing. While fresh ground argan almonds are characterized by only seven aroma active compounds, in argan oil from unroasted and roasted almonds, 22 and 35 aroma active compounds are found, respectively. As a result of the roasting process, 14 aroma active compounds with dilution factors >64 are detected in the oil by GC‐olfactometry. 17 aroma active compounds show significant differences between the three different argan oil qualities. These compounds are used to differentiate the quality of argan oil from the market. Practical Application: Argan oil belongs to the high‐price oils on the market but sometimes the sensory quality of the oil contradicts the positive image that has been built up for oil by unpleasant cheese‐like and fusty sensory attributes. Although some information about the composition of the volatile compounds of cold‐pressed argan oil from unroasted and roasted kernels is available, the knowledge about compounds that are typical for the aroma of argan oil is important in order to develop analytical methods for the classification of different argan oil qualities. This reduces the work for a panel group that is often time and labor consuming and sometimes the results are not reliable. The present paper demonstrates which volatile compounds show significant differences between argan oil from unroasted and roasted argan almonds as well as roasted almonds obtained from goat‐digested fruits allowing a differentiation of these oils.     

Fish oil sensory properties can be predicted using key oxidative volatiles

The high level of PUFA in fish oil, primarily eicosapentaenoic acid (EPA) and DHA result in rapid oxidation of the oil. Current methods used to assess oxidation have little correlation with sensory properties of fish oils. Here we describe an alternative method using solid phase microextraction (SPME) combined with GC‐MS to monitor volatile oxidation products. Stepwise discriminant function analysis (DFA) was used to classify oils characterized as acceptable or unacceptable based on sensory analysis; a cross‐validated success rate of 100% was achieved with the function. The classification function was also successfully validated with tasted samples that were not used to create the method. A total of 14 variables, primarily aldehydes and ketones, were identified as significant discriminators in the classification function. This method will be useful as a quality control method for fish oil manufacturers. Practical applications: This paper describes an analytical method that can be used by fish oil manufacturers for quality control purposes. Solid phase microextraction and GC‐MS were used to monitor volatile oxidation products in fish oil. These data, combined with results of analyses by a sensory panel, were used to create a function that classified fish oil samples as acceptable or unacceptable. The volatile oxidation products used to in the function were primarily aldehydes and ketones. This method can be used by fish oil manufacturers as an alternative to expensive sensory panels.     

Effects of frying oil composition on potato chip stability

Potato chips were fried in six canola (low-erucic acid rape-seed) oils under pilot-plant process settings that represented commercial conditions. Oil samples included an unmodified canola oil and oils with fatty acid compositions modified by mutation breeding or hydrogenation. Chips were fried for a 2-d, 18-h cycle for each oil. Chips and oil were sampled periodically for sensory, gas-chromatographic volatiles and chemical analyses. Unmodified canola oil produced chips with lower flavor stability and oxidative stability than the other oils. The hydrogenated oil imparted a typical hydrogenation flavor to the chips that slightly affected overall quality. the modified canola oil (IMC 129) with the highest oleic acid level (78%) had the lowest content of total polar compounds and the lowest total volatile compounds at most of the storage times; however, the sensory quality of the potato chip was only fair. The potato chip with the best flavor stability was fried in a modified/blended oil (IMC 01-4.5/129) with 68% oleic acid, 20% linoleic acid and 3% linolenic acid.     

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.     

Determination of trans fatty acids in cold pressed oils and in dried seeds

The adulteration of cold pressed oils (CPO) by refining or by blending with refined oils leads to an increase in their trans fatty acid (TFA) contents. The regulations of the European Union (EU) lay down strict processing conditions without any steam treatment for native olive oils and provide limits for TFA. However, German regulations allow a “steam washing” for CPO other than native olive oil and do not limit TFA. Thus, the TFA contents of such oils might exceed the limits for native olive oil. Modern capillary GLC serves as a quick tool for the detection of TFA. However, care should be taken to avoid the formation of TFA as artefacts during analysis. We evaluated the TFA contents in several oils labelled as “cold pressed” and the formation of TFA during “steam washing” and deodorization. Analysis of some seeds indicates that preliminary drying of the seeds may also contribute to TFA content.     

AOCS collaborative study on sensory and volatile compound analyses of vegetable oils

An AOCS collaborative study was conducted to determine the effectiveness of sensory analysis and gas chromatographic analyses of volatile compounds in measuring vegetable oils for levels of oxidation that ranged from none to high. Sixteen laboratories from industry, government, and academia in Canada and the United States participated in the study to evaluate the flavor quality and oxidative stability of aged soybean, corn, sunflower, and canola (low-erucic acid rapeseed) oils. Analytical methods included sensory analyses with both flavor intensity and flavor quality scales and gas-chromatographic volatiles by direct injection, static headspace, and dynamic headspace (purge and trap) techniques. Sensory and volatile compound data were used to rank each of the oils at four levels of oxidation—none, low, moderate, and high. For soybean, canola, and sunflower oils, 85–90% of laboratories correctly ranked the oils by either analysis. For corn oil, only 60% of the laboratories ranked the samples according to the correct levels of oxidation by either analysis. Variance component estimates for flavor scores showed that the variation between sensory panelists within laboratories was lowest for the unaged oils. As storage time increased, the variance also increased, indicating that differences among panelists were greater for more highly oxidized oils. Between-laboratory variance of sensory panel scores was significantly lower than within-laboratory variance.     

Differences in Oxidative Stability,Sensory Properties,and Volatile Compounds of Pepper Aromatized Sunflower Oils Prepared by Different Methods during Accelerated Storage

The study aims to compare the differences in the oxidative stability, sensory properties, and volatile compounds during accelerated storage of pepper aromatized sunflower oil (PASO) samples prepared by maceration method (PASO-M), co-pressing method (PASO-C), and direct addition method (PASO-A), respectively. The results exhibit that their oxidative stability is in the relative order: PASO-A > PASO-C > PASO-M. Meanwhile, the PASO-A sample is the most preferable aromatized sunflower oil by consumers according to sensory analysis. In addition, a total of 83 volatile compounds are identified in the three PASO samples during the storage, and the principal component analysis (PCA) shows that their volatile compounds are quite different at the initial stage of the storage. Still, they are similar among each other from the middle of storage period. As consequence, the aromatized sunflower oil sample prepared by the direct-addition method during the storage possesses better oxidative stability and sensory attributes, and there is not much difference among their volatile compounds, indicating that the aromatized sunflower oil prepared by direct-addition method can be developed as promising aromatized sunflower oil. Practical applications: This study shows that aromatization increases oxidative stability and sensory properties of sunflower oil. By this way some sunflower oils with special sensory properties are obtained: special smell and taste, special color, etc. These peppers aromatized sunflower oils can be used to increase taste and smell in some dishes. For example, they can be used in some salads and some roast meats to give more taste and color.