European Journal of Lipid Science and Technology Latest Content

Factors affecting the separation of the reaction mixture after transesterification of rapeseed oil

Martin Hájek, Franti[scaron]ek Skopal — 2008-07-16T07:25:00Z

The most used method of biodiesel production is the transesterification of vegetable oils by a basic homogeneous catalyst. A heterogeneous reaction mixture is formed by this process which contains two phases: an ester phase and a glycerol phase. From this mixture, biodiesel is gained by sedimentation. The quality and quantity of both phases are affected by the conditions of the sedimentation process. It was studied how the conditions (independent variables: temperature of separation, amount of added water, time of sedimentation, etc.) affect the quantity and the quality of both phases (dependent variables). The Plackett-Burman statistic system was used for experiment planning. The relationship between independent and dependent variables was found and described by multidimensional linear regression. The created model allows the calculation of the optimum conditions of biodiesel production so that the quality of the biodiesel fulfills the EN 14214.

The concentration of tocols from rice bran oil deodorizer distillate using solvent

Soon-Nam Ko, Sun-Mi Lee, In-Hwan Kim — 2008-07-16T07:25:00Z

Tocols (tocopherols + tocotrienols) have been concentrated efficiently from rice bran oil (RBO) deodorizer distillate using solvent at low temperature. The levels of total tocols, total tocopherols, and total tocotrienols in RBO deodorizer distillate (starting material) were 31.5, 14.9, and 16.6 mg/g, respectively. Nine different solvents were tested, and acetonitrile was selected as the optimal solvent for concentrating tocols from the RBO deodorizer distillate. There was a significant (p <0.05) increase in the tocol level of the liquid fractions with decreasing temperature, for incubation temperatures up to -20 °C. In addition, significant differences (p <0.05) were observed in the relative percentages of [alpha]-tocopherol, [gamma]-tocopherol, [alpha]-tocotrienol, and [gamma]-tocotrienol between the raw sample and liquid fractions obtained at different temperatures using acetonitrile as the solvent. The concentration of the tocols from the RBO deodorizer distillate was temperature dependent, and a maximum of 89.9 mg/g was attained in the liquid fraction at - 40 °C. The relative percentage of tocotrienol homologs in the liquid fraction obtained at - 40 °C was approximately 80%. With acetonitrile as the solvent, the optimal temperature for concentrating the tocols from RBO deodorizer distillate was -20 °C when yield was considered.

Pattern recognition of lipase-catalyzed or chemically interesterified fat blends containing n-3 polyunsaturated fatty acids

2008-07-16T07:25:00Z

The feasibility to discriminate among samples of different fat blends prior and after inorganic or lipase-catalyzed interesterification, via pattern recognition techniques [principal component analysis (PCA) and discriminant analysis (DA)], was investigated. Blends I and II, consisting of mixtures of palm stearin, palm kernel oil and a concentrate of triacylglycerols (TAG) rich in n-3 polyunsaturated fatty acids (EPAX 4510TG or EPAX 2050TG) were used. These blends, prior (64 samples) and after interesterification, catalyzed by an immobilized Thermomyces lanuginosa lipase (Lipozyme TL IM, 54 samples) or by sodium methoxide (10 samples), were characterized by their acylglycerol profiles (25 chromatographic peaks) and solid fat content (SFC) at 10, 20, 30 and 35 °C. PCA on the multivariate data (i) showed that the initial samples were characterized by higher SFC and higher contents of high-melting TAG and (ii) suggested two separate clusters of initial and interesterified samples. DA was performed on the multivariate data to determine which of the 29 variables have discriminative power. When the 124 samples, characterized by their acylglycerols, were grouped into (i) initial and interesterified samples of blends I or II (four groups) or (ii) also by the catalyst used (six groups), 98.4% of the samples were correctly classified.

Analytical evaluation of six monovarietal virgin olive oils from Northern Tunisia

2008-07-16T07:25:00Z

The characterization of virgin olive oils from six Tunisian cultivars, namely Chétoui, Ain Jarboua, Jarboui, Regregui, Rekhami and Neb Jmel, grown in Nebeur (a region of the Kef) was carried out. These cultivars dominate their natural habitats, but with the exception of the Chétoui cultivar they are only scattered throughout the nation. Several analytical parameters were evaluated; these include quality index, fatty acid composition, chlorophylls, carotenoids, sterols, [alpha]-tocopherol and phenolic compounds. Their relationship with oxidative stability was also tested. The main phenols found were tyrosol, hydroxytyrosol, the dialdehydic form of elenolic acid linked to tyrosol and hydroxytyrosol, oleuropein aglycon and pinoresinol. These phenolic compounds, the colorimetric total phenol content and o-diphenols showed significant correlations with oxidative stability. Furthermore, most of the analytical parameters of the oils that were determined in this study were greatly influenced by genetic factors (cultivar).

Thermostability of genetically modified sunflower oils differing in fatty acid and tocopherol compositions

2008-07-10T07:38:00Z

The objective of the study was to investigate the performance at frying temperature of a new sunflower oil with high content of oleic and palmitic acid (HOHPSO) and containing [gamma]-tocopherol as the most abundant natural antioxidant. HOHPSO either containing [alpha]- or [gamma]-tocopherol (HOHPSO-[alpha] and HOHPSO-[gamma], respectively) were obtained from genetically modified sunflower seeds and refined under identical conditions. The oil stability against oxidation, as measured by Rancimat at 120 °C, was much higher for the oil containing [gamma]-tocopherol, suggesting the higher effectiveness of [gamma]-tocopherol as compared to [alpha]-tocopherol to delay oxidation. Experiments at high temperature (180 °C) simulating the conditions applied in the frying process clearly demonstrated that, for the same periods of heating, the oil degradation and the loss of natural tocopherol were significantly lower for the oil containing [gamma]-tocopherol. Comparison of different genetically modified sunflower oils with different fatty acid compositions confirmed that oil degradation depended on the fatty acid composition, being higher at a higher degree of unsaturation. However, the loss of tocopherol for a similar level of oil degradation was higher as the degree of unsaturation decreased. Overall, the results showed that HOHPSO-[gamma] had a very high stability at frying temperatures and that mixtures of HOHPSO-[alpha] and HOHPSO-[gamma] would be an excellent alternative to fulfill the frying performance required by the processors and the vitamin E content claimed by the consumers.

Undecylenic acid: A valuable renewable building block on route to Tyromycin A derivatives

2008-07-10T07:38:00Z

A key intermediate for the synthesis of Tyromycin A, a C-20 tetrachlorodicarboxylic acid, was produced in six steps starting with the dimerization of methyl 10-undecenoate which was obtained from a renewable resource, e.g. castor oil. The acyloin condensation product was then oxidized, transformed to the diene, followed by ozonization, chlorination and finally oxidation to the corresponding tetrachlorodicarboxylic acid.

Lipid adsorption capacities of magnesium silicate and activated carbon prepared from the same rice hull

Ozgul O. Taspinar, Sevil Ozgul-Yucel — 2008-07-10T07:38:00Z

This study is a comparison of the lipid adsorption capacities of synthetic magnesium silicate and activated carbon produced from rice hulls of the same origin. The lipids examined were the free fatty acids, diacylglycerols and monoacylglycerols of frying oils. Pure oleic acid, an unused sunflower frying oil and a used sunflower frying oil were used in the experiments. The produced adsorbents, magnesium silicate and activated carbon, have surface areas of 680 and 43 m2/g, respectively. The lipid adsorption capacity of the produced magnesium silicate was found as 644 mg polar compounds/g adsorbent and it is higher than the capacities of the industrial adsorbents, Magnesol XL and activated carbon. This value is only 368 mg polar compounds/g adsorbent for the activated carbon produced from the same-origin rice hull.

The effect of malaxation temperature on the virgin olive oil phenolic profile under laboratory-scale conditions

Alessandro Parenti, Paolo Spugnoli, Piernicola Masella, Luca Calamai — 2008-07-10T07:38:00Z

The relationship between olive paste malaxation temperature and the concentration of olive oil hydrophilic phenols (HP), i.e. simple phenols, secoiridoids and lignans, was investigated. Malaxation experiments were performed at laboratory scale for 45 min at 21, 24, 27, 30, 33 and 36 °C. A significant (p <0.05) increment of total phenols concentration was found with a maximum at 27 °C, whereas for higher temperatures (30-36 °C) a progressive decrement was observed. A similar pattern was recorded approximately for all the secoiridoid compounds, i.e. a quasi-linear increment of concentrations with increasing temperature until 30 °C, followed by a marked decrease in correspondence with the higher malaxation temperature (33 and 36 °C). The amount of simple phenols increased linearly with increasing temperature and no decrements were observed up to the maximal temperature investigated (36 °C), while no significant differences were found for lignans. A small increment of peroxide values and total chlorophyll was recorded as a function of the increasing malaxation temperature, whereas no differences were observed in the free acidity. The results highlight that there is not a univocal relationship between HP concentration and malaxation temperature. An equilibrium between degradation (chemical and biochemical oxidation and hydrolysis) and transfer (partitioning) phenomena was hypothesized.

The quality and volatile-profile changes of camellia oil (Camellia oleifera Abel) following bleaching

2008-07-10T07:38:00Z

Bleaching is a necessary step in the production of refined camellia oil (Camellia oleifera Abel) since crude oil has a dark brown color, due to pigments extracted from the seed coat during pressing, which is unacceptable to consumers. In order to understand the quality change and oxidative state of camellia oil in the bleaching step, measurements of various quality parameters, i.e. peroxide value (POV), free fatty acids (FFA), UV absorbance, and the volatile profiles of crude and bleached oils, were carried out. The results showed that FFA, K270, and K232 increased, whereas POV decreased, with increase of the activated earth dosage of 0-4% and of bleaching time from 0 to 40 min at 110 °C. As the amount of activated earth was increased from 0 to 4% with bleaching at 110 °C for 30 min, various classes of volatile compounds increased in concentration: aldehydes (23.7 µg/g), alcohols (13.2 µg/g), esters (8.0 µg/g), alkenes (2.0 µg/g) and ketones (1.9 µg/g). Likewise, when bleaching was carried out at 110 °C with 3% activated earth and the bleaching time varied between 0 and 40 min, the concentrations of volatile compounds also increased: aldehydes (27.7 µg/g), alcohols (18.2 µg/g), esters (7.3 µg/g), ketones (3.2 µg/g) and alkenes (0.6 µg/g). These findings indicate that hydroperoxides in the oil were decomposed into lower-molecular-weight products in the process of bleaching and that the extent of this decomposition can be controlled by time and amount of activated earth.

Polymers from renewable resources: Bulk ATRP of fatty alcohol-derived methacrylates

Gökhan Çayli, Michael A. R. Meier — 2008-06-12T04:23:00Z

Copper-mediated atom transfer radical polymerization (ATRP) of lauryl methacrylate (LMA) and other long-chain methacrylates was investigated in bulk at 35 °C by using CuCl/N,N,N[prime],N[prime],N[prime][prime]-pentamethyldiethylenetriamine (PMDETA)/tricaprylylmethylammonium chloride (Aliquat®336) as the catalyst system and ethyl 2-bromoisobutyrate (EBIB) as the initiator. The investigated monomers can be derived from fatty alcohols and are therefore an important renewable resource for a sustainable development of our future. The amounts of ligand, Aliquat®336 and CuCl were optimized and the effect of their concentrations on the control of the polymerization and the observed conversions were investigated. It was found that a molar ratio of EBIB/CuCl/Ligand/Aliquat®336 of 1 : 1 : 3 : 1 provided the highest conversions of LMA and the best controlled polymerizations. These optimized conditions allowed for the synthesis of poly(lauryl methcarylate)s with different targeted DP (25, 50, 75, 100, 120, 240, and 500), including high-molecular-weight polymers with narrow molecular weight distributions. In addition, methacrylate monomers were prepared from fatty alcohols (capric, myristic, palmitic, stearic) and polymerized using the developed procedure to obtain polymers with the same DP and different chain lengths (C10, C12, C14, C16, and C18) of pending alkyl groups. Finally, the thermal properties of these polymers were examined by differential scanning calorimetry and thermogravimetric analysis.

N-3 enrichment of pork with fishmeal: Effects on production and consumer acceptability

2008-06-12T04:23:00Z

This study aimed to develop pork products of acceptable organoleptic quality enriched with long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA). Female pigs were fed a finisher diet containing 15% PorcOmegaTM tuna fishmeal or a commercial diet. Pigs and rations were weighed weekly. The feed conversion ratio was significantly lower in pigs fed fishmeal than in controls (2.61 ± 0.01 versus 2.96 ± 0.06, p <0.05). After 6 weeks, the pigs were butchered and the fatty acid contents of selected pork products were analyzed by gas chromatography. Shelf life was tested by thiobarbituric acid-reactive substances (TBARS), initially and after 5 days of cold storage, and sensory qualities were evaluated after cooking. LC n-3 PUFA contents of pork products from pigs fed fishmeal were higher than in controls (steak 300%, stir-fry 250%, diced 520%, mince 480%, sausage 360%; p <0.05 in all cases). There were no differences between n-3-enriched and regular pork in either TBARS content of stored raw products or sensory characteristics after cooking. Incorporating fishmeal in the finisher diet resulted in greater feed efficiency and production of nutritionally enhanced pork products with organoleptic profiles and stability comparable to those of regular pork.

Supplemental dietary flaxseed oil affects both neutral and phospholipid fatty acids in cultured tilapia

2008-06-12T04:23:00Z

This work aimed to evaluate the neutral lipid (NL) and phospholipid (PL) classes in tilapia (Oreochromis niloticus) muscle tissue. Tilapias were raised in captivity for a period of 5 months with increasing levels (0, 1.25, 2.50, 3.75, and 5.00%) of flaxseed oil [source of [alpha]-linolenic acid (LNA), 18:3n-3] in substitution for sunflower oil (control). The NL/PL ratio was 1.9, and 45 fatty acids were determined for both classes of lipid. The class totals of n-3 acids always increased in all treatments, while the totals for n-6 acids always decreased (p <0.05). For a given level of flaxseed oil, the LNA contents were consistently higher, including EPA (20:5n-3) and DHA (22:6n-3). Arachidonic acid (20:4n-6) remained high in the PL but was reduced as levels of dietary flaxseed oil were increased. The n-6/n-3 ratios decreased significantly with the rise in flaxseed oil content in all treatments, and highly unsaturated fatty acid contents increased with the levels of flaxseed oil. Overall, the influence of flaxseed oil on the fatty acid composition in the contributing NL and PL classes was to increase n-3 PUFA, thus raising the nutritional value of this freshwater fish meat and, consequently, contributing to the health of consumers.

Parametric study of biodiesel production from used soybean oil

Mamdouh Allawzi, Munther Issa Kandah — 2008-06-12T04:23:00Z

Biodiesel, an alternative diesel fuel derived from vegetable oil, animal fat, or waste vegetable oil (WVO), is obtained by reacting the oil or fat with an alcohol (transesterification) in the presence of a basic catalyst to produce the corresponding mono-alkyl esters. In this work, the effect of the catalyst KOH-to-WVO ratio, ethanol concentration, and time of reaction on the biodiesel yield were investigated. The transesterification reaction was performed at a constant temperature (35 °C) in order to minimize the cost of heating and ethanol evaporation. A 23 complete factorial design on biodiesel yield (Y) was performed using low and high levels of operating variables: KOH concentration (9-14 g/L), ethanol concentration (30-40 vol-%) and time (30-40 min). The complete factorial model that can be used to fit the data was determined. The model shows that interactions exist among the parameters and that the parameters, or factors, do not operate independently on the response (biodiesel yield). The highest yield was obtained in the first 30 min of reaction time. The results indicate that the highest yield was 78.5 vol-% using a KOH-to-WVO ratio of 12 g/L and 30 vol-% ethanol. The ASTM tests indicate that the biodiesel properties are within the biodiesel standard limits.

Oil yield and compressibility modeling during microscale expression: Criteria for linseed breeding

Raphaëlle Savoire, Jean-Louis Lanoisellé, Hélène Ducatel, Eugène Vorobiev — 2008-06-10T06:31:00Z

Seven linseed varieties were harvested at seven times before complete maturity. Microscale oilseed expressions were subsequently carried out on it. A pressure of 10 MPa was applied for 1 h under uniaxial stress. The results were characterized in terms of oil, water and mucilage content, harvest date and oil yield. The piston displacement versus time (creep curves) was described by a four-Kelvin-Voigt elements viscoelastic model. Parameters were derived from the model, such as the mechanical properties of seeds (compressibility moduli), showing that the viscoelastic model fits well the experimental data (R² [ap] 0.999). The modeling parameters were combined with some biochemical data in order to predict the kinetics of oil extraction.

Bitter off-taste in stored cold-pressed linseed oil obtained from different varieties

Ludger Brühl, Bertrand Matthäus, Anne Scheipers, Thomas Hofmann — 2008-05-19T09:01:00Z

Freshly pressed linseed oil shows a delicate nutty flavor. However, after only 1 day of storage, a bitter off-taste develops. It is caused mainly by the formation of a cyclic octa-peptide named cyclolinopeptide E (CLE) containing the oxidized amino acid methionine. A simple and fast determination by solid-phase extraction and high-performance liquid chromatography with UV detection has been developed in order to measure the formation of this cyclic peptide during storage in correlation with the increasing bitter off-taste of the oil, which was determined by a sensory panel. The development of this bitter off-taste was analyzed in several oils prepared from linseed of a single variety from seeds obtained during a growing test. Highest bitterness was perceived in oil from the variety Eurodor, corresponding to CLE contents of 925 mg/kg, and lowest bitterness was perceived in oil from the variety Baladin, corresponding to a CLE content of 485 mg/kg. In some varieties, additional bitter compounds might be present in significant amounts.

Great globe thistle fruit (Echinops sphaerocephalus L.), a potential new oil crop

2008-02-20T08:16:00Z

New plant oil crops are desirable as renewable resources for energy, for food purposes, and as building blocks in chemical synthesis. Fruit oil of Echinops sphaerocephalus was characterized by a high content of linoleic acid (over 70% of total fatty acids) and by a high tocopherol content (530-970 mg/kg oil). The majority was [alpha]-tocopherol. Echinops sphaerocephalus plants may be cultivated in agricultural dimensions, and fruits may be obtained by a combine harvester. Echinops quinoline alkaloids present a useful by-product of the oil production.

Enzymatic biodiesel production: Technical and economical considerations

Per Munk Nielsen, Jesper Brask, Lene Fjerbaek — 2008-07-16T07:25:00Z

It is well documented in the literature that enzymatic processing of oils and fats for biodiesel is technically feasible. However, with very few exceptions, enzyme technology is not currently used in commercial-scale biodiesel production. This is mainly due to non-optimized process design and a lack of available cost-effective enzymes. The technology to re-use enzymes has typically proven insufficient for the processes to be competitive. However, literature data documenting the productivity of enzymatic biodiesel together with the development of new immobilization technology indicates that enzyme catalysts can become cost effective compared to chemical processing. This work reviews the enzymatic processing of oils and fats into biodiesel with focus on process design and economy.

Oxidation of unsaturated fatty acid derivatives and vegetable oils

Angela Köckritz, Andreas Martin — 2008-07-16T07:25:00Z

The present review reports the current literature of the last 10 years on selective oxidation reactions of fatty acid derivatives and vegetable oils. The work is structured in divisions including epoxidation, radical oxidations, Wacker-type oxidation, dihydroxylation and C=C double bond cleavage.

Argan oil: Occurrence, composition and impact on human health

Zoubida Charrouf, Dominique Guillaume — 2008-07-10T07:38:00Z

Edible argan oil is traditionally prepared by Berber women who manually crunch the roasted kernels of Argania spinosa fruits. Unroasted kernels furnish a cosmetic-grade oil. Argan groves are currently shrinking due to unfavorable conditions. To stop this trend, a program aimed at increasing the argan tree economical value is in progress in Morocco. Its concept is that the natives will preserve argan trees only if the major part of the wealth resulting from the argan grove production directly benefits them. Because of its high dietary value, argan oil has appeared as the best derivative to rapidly satisfy such assumption. Consequently, year after year, cooperatives have been implanted to produce argan oil of high quality on a large scale. The delicate hazelnut taste of argan oil, combined with its high level in unsaturated fatty acids, has allowed its swift commercial success and, nowadays, argan oil of standardized quality is marketed worldwide. Moroccan farmers are now beginning to plant argan trees, confirming the full success of this ambitious program. This review summarizes the methods used to prepare argan oil, its composition, the strategies available to certify argan oil quality, and finally the impact of argan oil on human health.

Virgin olive oil - Chemical implications on quality and health

Diego L. García-González, Ramón Aparicio-Ruiz, Ramón Aparicio — 2008-05-30T05:52:00Z

This paper provides a brief review of the most significant characteristics of olive oil. Processing, composition, authentication, sensory quality and health benefits are the examined aspects. In all these issues, the most recent challenges are described, most of them related to new environmental problems, emerging procedures of adulteration and new chemical features to detect them, and a deep knowledge of the relationship between olive oil consumption and the incidence of some diseases other than cardiovascular malfunction.

Metathesis as a versatile tool in oleochemistry

Anastasiya Rybak, Patrice A. Fokou, Michael A. R. Meier — 2008-05-21T01:25:00Z

Olefin metathesis, awarded with the Nobel Prize in Chemistry 2005 for Chauvin, Grubbs and Schrock, has emerged as a powerful tool for organic as well as polymer chemistry. In oleochemistry, this reaction is well known and has been applied for many decades. Examples include the functionalization of the double bonds of different oleochemicals or the (direct) polymerization of plant oils via metathesis. More recent developments, particularly the development of better and more robust catalysts, allow for highly efficient cross-metathesis reactions opening new possibilities for the direct introduction of chemical functionalities. Within this contribution, the development of metathesis in oleochemistry will be discussed, covering self-metathesis as well as more recent developments in the field of cross-metathesis that lead to desired platform chemicals.

Virgin hemp seed oil: An interesting niche product

Bertrand Matthäus, Ludger Brühl — 2008-05-19T09:01:00Z

Virgin hemp seed oil is not widespread on the market, although it is characterised by an interesting fatty acid composition with a high content of polyunsaturated fatty acids. Linoleic acid is the predominant fatty acid, which comes, together with [alpha]-linolenic acid (18:3n-3), to approximately 80% of the total fatty acids. From a nutritional point of view, up to 7% [gamma]-linolenic acid (18:3n-6) and 2.5% stearidonic acid (18:4n-3) are very interesting. The total amount of tocopherols is high between 80 and 110 mg/100 g, with [gamma]-tocopherol as the main tocopherol (85%). Due to the high amount of unsaturated fatty acids, hemp seed oil is very susceptible to oxidative deterioration, which results in a fast impairment of the oil during storage. In addition, the high amounts of chlorophyll in the oil due to harvesting of high amounts of immature seeds require light protection, which is often neglected because of merchandising purposes. The virgin oil is characterised by a nutty taste with a slightly bitter aftertaste. The use of virgin hemp seed oil is recommended during mild processing of food without heat.

Production technology and characteristics of Styrian pumpkin seed oil

Gilbert O. Fruhwirth, Albin Hermetter — 2008-05-19T09:01:00Z

Cucurbita pepo subsp. pepo var. Styriaca, the so-called Styrian oil pumpkin, is a phylogenetically young member of the Cucurbita spp. A single mutation occurred only in the 19th century and led to dark green seeds with stunted outer hulls. This mutation facilitated the production of Styrian pumpkin seed oil that became a regional specialty oil in the south-eastern part of Europe during the last few decades. We describe in this article the production and economic value of this edible specialty oil as well as the most important parameters relevant for its quality. Furthermore, we report on its molecular composition including fatty acids, vitamins, phytosterols, minerals, polyphenols, and those compounds that are responsible for its color, taste and flavor. Finally, information is provided on potential contaminants of Styrian pumpkin seed oil as well as its putative beneficial health effects.

Borage and evening primrose oil

N. A. Michael Eskin — 2008-04-25T03:39:00Z

The paper gives a short overview about the production and composition of borage (Borago officinalis) and evening primrose (Oenothera biennis) oil considering special aspects of the production as cold-pressed oil. Both oils are characterized by a remarkable amount of [gamma]-linolenic acid, which has some nutritional advantages. The fatty acid composition of evening primrose oil is dominated by linoleic acid with about 72% and about 13% [gamma]-linolenic acid, while borage oil consists of twice the amount of [gamma]-linolenic acid and only 38% linoleic acid. The amount of saturated fatty acids is higher in borage oil. The tocopherol composition of both oils is dominated by [gamma]-tocopherol, with borage oil containing twice the amount compared to evening primrose oil.

Virgin grape seed oil: Is it really a nutritional highlight?

Bertrand Matthäus — 2008-03-13T08:16:00Z

In comparison to refined grape seed oil which is neutral in taste and smell, the virgin oil is characterized by a pleasant vinous and fruity aroma, which also reminds of raisins if high-quality raw material is used for the production. Difficulties arise from the susceptibility of the raw material to microbial and enzymatic deterioration as a result of the high moisture content after pressing the juices from the grapes. Grape seed oil has a high content (70%) of linoleic acid, whereas the total part of unsaturated fatty acids amounts to about 90%. In comparison to other edible oils, the oil contains, in addition to tocopherols, antioxidant-effective tocotrienols. During the oil pressing process, only a small amount of phenolic compounds is transferred into the oil (0.01 mg/g), while most of these nutritionally interesting components remain in the press cake. Here, the content of phenolic compounds is about 2000 times higher. During storage of virgin grape seed oil, the pleasant sensory attributes change, and more and more degradation products like ethyl acetate, acetic acid or ethanol are detectable. Parts of the seed material, which come into the oil during pressing, result in a faster impairment of the oil.

Why is it so difficult to produce high-quality virgin rapeseed oil for human consumption?

Bertrand Matthäus, Ludger Brühl — 2008-03-13T08:16:00Z

Virgin rapeseed oil becomes increasingly popular for the consumer because of the pleasant seed-like and nutty taste and smell. The oils are produced in small and medium-sized facilities by extraction of rapeseed using only a screw press and purifying the oil by sedimentation or filtration. Thus, the producers have no chance to improve the oil quality if the seed quality is bad. Therefore, it is an art to produce high-quality virgin rapeseed oil that is accepted by the consumer. The most important step in the production chain of virgin rapeseed oil is the period after harvest until the processing, while extraction of the oilseed and purification has only a minor influence on the oil quality. The paper describes the pitfalls during the production of virgin rapeseed oil which primarily wait for the producer during storage of the seeds. Improper storage conditions result in increased metabolic processes in the seeds and an increase of the populations of microorganisms and insects, which finally leads to the degradation of nutrients and the formation of unpleasant aroma compounds.