Cold-pressed Rapeseed Oil Research Articles

Yeast lipids as a sustainable source of nutrients in dairy products analogs

The main objective of the study was to develop a concept for the use of oleaginous Yarrowia lipolytica biomass and single-cell oil (SCO) as vegan food components. SCOs were derived from the wild-type strain KKP 379, cultured in media containing glucose, cold-pressed rapeseed oil, and cost-effective carbon sources such as molasses and post-frying rapeseed oil. Confocal microscopy analysis of the biomass and detailed analysis of the composition of fatty acids, sterols, and polycyclic aromatic hydrocarbons (PAHs) in the extracted lipids were conducted. The choice of substrates allowed to obtain SCO from post-frying rapeseed oil medium with the desired yield (3.27 g/L), composition (UFA - 93.34%), and high oxidative stability (Τmax-204.94 min, 120°C, isothermal conditions). The content of hexane as an extraction solvent was also evaluated, which also complied with European Union requirements (0.0007 mg/kg). All SCOs from Y. lipolytica met the European Commission's requirements for marketed oils and fats for maximum levels of benzo[a)pyrene and the sum of benzo[a]pyrene, benzo[a]anthracene, benzo[b]fluoranthene and chrysene. The content of benzo[a]pyrene was in the range of 0.52-1.71 μg/kg. Finally, the oleaginous yeast biomass was subsequently applied as an enrichment additive in plant-based analogs of Camambert-type cheese, and its potential for use in fat-rich vegan food products was discussed.

Effect of different pretreatment techniques on quality characteristics, chemical composition, antioxidant capacity and flavor of cold-pressed rapeseed oil

This study investigated the effects of different pretreatment techniques (microwave heating, infrared heating, oven heating and enzymatic methods) on the quality of cold-pressed rapeseed oil (CPRO) with commercially available first-grade pressed rapeseed oil (CFO) as a control. The results showed that CPRO is more nutritionally valuable than CFO while meeting the quality standard without refining. Microwave heating pretreatment's cold-pressed rapeseed oil (MHO) exhibited a higher oil yield (70.83 ± 0.40 %), a higher trace active ingredient content (tocopherol 53.79 ± 0.19 mg/100 g, phytosterol 726.98 ± 4.14 mg/100 g, and polyphenol 87.09 ± 0.08 mg GAE/100 g), and a stronger antioxidant capacity. Correlation analysis and multiple linear regression analysis indicated that antioxidant capacity was mainly related to the content of α-tocopherol and polyphenols. Microwave heating promoted the degradation of the Maillard reaction and glucosinolates, significantly improving the flavor of CPRO. Therefore, microwave heating is a promising pretreatment technology for the production of high-quality CPRO.

The Influence of Storage Conditions of Cold-Pressed Rapeseed Oil on Its Quality Parameters

Stored vegetable oil undergoes numerous processes, i.e., oxidation, hydrolysis, and thermal polymerization. As a result, its quality and organoleptic parameters deteriorate. The content of natural chlorophyll and carotenoid pigments determines the color of rapeseed oil. Almost imperceptible changes in the color of the oil may indicate the deterioration of its quality. Therefore, vegetable oils must be stored in the appropriate conditions to protect them against unfavorable factors leading to deterioration. This publication examines and describes the influence of storage temperature, type of packaging (clear glass, colored glass, PET), and presence of an oxygen-free atmosphere on the quality of stored cold-pressed rapeseed oil for three and six months. Changes in the following parameters were verified: the content of chlorophyll and carotenoid pigments, oil color (measured by the CIE Lab method), acid value, and radical scavenging activity (%RSA) by the ABTS (diammonium 2,2′-azinobis[3-ethyl-2,3-dihydrobenzothiazole-6-sulphonate) method. The decrease in the content of natural dyes was 7 to 87% after three months, depending on storage conditions, and after six months, from 12 to 97%. To determine which factors were responsible for the change in the physicochemical properties of the oil during storage, a principal component analysis (PCA) was performed.

Effects of Centrifugation on the Oxidative Stability and Antioxidant Profile of Cold-Pressed Rapeseed Oil during Storage

The recognition and growing consumption of cold-pressed rapeseed oil (CPRO) is due to by its unique, health-promoting properties; it is a rich source of omega-3 fatty acids and antioxidants. Nevertheless, the high content of unsaturated fatty acids and plant tissue particles makes CPRO more susceptible to oxidation. These pro-oxidant plant particles can be eliminated via centrifugation, thus improving the quality and stability of CPRO. Therefore, we aimed to determine whether the clarification of CPRO via centrifugation affects its quality parameters, pigment and phenolic profile, and antioxidant properties. These characteristics were analyzed and compared between centrifuged CPRO and CPRO clarified via natural decantation. Changes were monitored for 6 months of oil storage at 22 °C. Based on the results, no changes in the oxidation profile were found between centrifuged CPRO and decantated CPRO. When the storage is longer than 1 month, centrifugation is more beneficial with regard to delaying hydrolytic deterioration, while decantation provides slightly better pigment and polyphenol profiles. We did not observe that centrifugation improved the oil’s antioxidant properties. Further research should be continued to establish the effects of centrifugation on CPRO quality, including parameters such as rapeseed quality, maturity degree, varieties, and stricter storage conditions.

Comprehensive two-dimensional gas chromatography-time of flight mass spectrometry as a tool for tracking roasting-induced changes in the volatilome of cold-pressed rapeseed oil

The aim of this study was to track changes in the volatilome of cold-pressed oil and press cakes obtained from roasted seeds and to combine it with the profile of non-volatile metabolites in a single study, in order to understand pathways of volatile organic compound (VOC) formation caused by thermal processing. Comprehensive two-dimensional gas chromatography-time of flight mass spectrometry was used for the analysis of VOCs in cold-pressed oils and corresponding press cakes obtained after roasting of seeds at 140 and 180 °C prior to pressing. Contents of primary metabolites (amino acids, saccharides, fatty acids) as well as selected secondary metabolites (glucosinolates, polyphenols) were determined, as many of them serve as precursors to volatile compounds formed especially in thermal reactions. After roasting, the formation of Maillard reaction products increased, which corresponded to the reduction of free amino acids and monosaccharides. Moreover, levels of the products of thermal oxidation of fatty acids, such as aldehydes and ketones, increased with the increasing temperature of roasting, although no significant changes were noted for fatty acids. Among sulphur-containing compounds, contents of the products and intermediates of methionine Strecker degradation increased significantly with the increasing temperature of roasting. Degradation of glucosinolates to nitriles occurred after thermal treatment. The results of this study confirmed that seed roasting before cold pressing has a significant effect on the volatiles, but also indicated roasting-induced changes in non-volatile metabolites of oil and press cake. Such an approach helps to understand metabolic changes occurring during rapeseed processing in cold-pressed oil production.Graphical

Potentially Toxic Elements (PTEs) in Refined and Cold-Pressed Vegetable Oils Distributed in Ahvaz, Iran: a Probabilistic Health Risk Assessment.

The concentration of potentially toxic elements (PTEs) in vegetable oils using inductively coupled plasma-optical emission spectrometry (ICP-OES) was measured. Probabilistic non-carcinogenic risk in consumers was estimated using the target hazard quotient (THQ) and total target hazard quotient (TTHQ) by Monte Carlo simulation (MCS) method. The highest content of PTEs was found in blend oil for As (0.39 ± 0.07mg/L), in cold-pressed rapeseed oil for Cd and Cu (0.07 ± 0 and 0.40 ± 0.06mg/L) respectively, in cold-pressed sunflower oil for Fe (0.15 ± 0.10mg/L), in refined sesame oil for Ni and Pb (0.44 ± 0.07 and 0.65 ± 0.07mg/L, respectively), and in cold-pressed sunflower and rapeseed oils for Zn (0.19 ± 0.04mg/L). THQ in adults and children due to individual vegetable oils (cold-pressed and refined vegetable oil) was lower than 1 value. TTHQ in adults and children due to consumption of cold-pressed vegetable oils was 0.05 and 0.26, and also refined vegetable oil was 0.51 and 0.33, respectively. TTHQ due to consumption of both types of oils was less than 1; therefore, the population is not at risk of non-carcinogenicity.

Changes in Quality of Cold-Pressed Rapeseed Oil with Sinapic Acid Ester-Gelatin Films during Storage.

In recent years, cold-pressed rapeseed oil (CPRO) has become an attractive health-beneficial product and a promising alternative to olive oil. However, a high level of unsaturated fatty acids renders a CPRO more susceptible to oxidative deterioration. Therefore, the effect of new gelatin strips with polyvinyl alcohol (GEL-PVA) and sinapic acid esters (ethyl sinapate-ESA; octyl sinapate-OSA, and cetyl sinapate-CSA) on the oxidative stability, antioxidant activity (AA), and total phenolic content (TPC) in CPRO samples was analyzed during accelerated storage. In addition, the antioxidant properties of the GEL-PVA films loaded with sinapic acid esters were studied. Interestingly, the CPRO stored in an amber glass marasca bottle containing GEL-PVA-ESA strips for 14 days had the highest AA, while the antioxidant potential was the lowest for oil without film strips. Furthermore, oil samples stored in bottles containing GEL-PVA-ESA and GEL-PVA-OSA strips for 14 days had higher antioxidant properties than the AA and TPC in fresh CPRO. Moreover, synchronous fluorescence (SF) spectroscopy and excitation-emission matrix (EEM) fluorescence spectroscopy were applied for the evaluation of changes in the main fluorescent components in CPRO samples during the accelerated storage. Overall, this study revealed that GEL-PVA films incorporated with sinapic acid esters enhanced the antioxidant potential of CPRO and delayed oxidative degradation by releasing amphiphilic antioxidants into the oil.

Effect of Different Extraction Methods on Quality Characteristics of Rapeseed and Flaxseed Oils

This study reports the effect of roasted pretreatment combined with screw press, hydraulic press, and Soxhlet extraction methods on various quality indexes of rapeseed and flaxseed oils, including the oil yield, sensory indexes (color, smell, clarity, viscosity, and colligation score), physicochemical properties (acid value, peroxide value, saponification value, moisture and volatiles), major components (fatty acid composition and triglyceride composition), and minor components (volatile compounds, total phenols, and vitamin E contents). The results indicated that the oil yield, sensory indexes, physicochemical properties, fatty acid composition, volatile compounds, total phenol, and vitamin E contents in vegetable oils have been significantly affected by different extraction methods. The yields of rapeseed and flaxseed oils of Soxhlet extraction method were increased by 30.10%–73.90% and 6.30%–54.40%, respectively, compared with other treatment groups. In addition, roasted pretreatment significantly increased the yields of oils by 4.10%–25.00% and 6.70%–23.15%, respectively, compared with the untreated group. The contents of linolenic acid and vitamin E in rapeseed and flaxseed oils extracted from screw press method were higher. In particular, the linolenic acid content of cold-pressed rapeseed oil extracted by screw press increased by 1.50%–23.80% compared with other treatment groups. In addition, the contents of vitamin E in cold-pressed rapeseed oil and flaxseed oil obtained by screw press increased by 1.22%–78.91% and 3.00%–18.80%, respectively. The Soxhlet extraction could improve oil yield and total phenol content, but the quality of the oil was inferior due to high acid values (0.93–3.36 mg KOH/g) and peroxide values (0.70–5.23 meq O2/kg). Furthermore, the hydraulic press method could extract vegetable oils with excellent sensory scores. The roasted pretreatment gives the rapeseed and flaxseed oils a good smell. The major volatile compounds in rapeseed and flaxseed oils were aldehydes, acids, alcohols, heterocycles, and ketones. Different extraction methods and pretreatment had no significant effect on the compositions and contents of triglycerides. This study provides a basic understanding on the selection of appropriate oil extraction techniques for oil extraction at a large scale.

Influence of two-stage harvesting on the properties of cold-pressed rapeseed (Brassica napus L.) oils

Rapeseed (Brassica napus L.) harvesting method is critical since it significantly determines the seed yield, oil quality, and industrial efficiency. This study investigated the influences of harvesting methods on the quality of cold-pressed rapeseed oil of two varieties. Oil color, peroxide value (POV), tocopherol content, fatty acid composition, and polarity of total polyphenols (PTP) contents of two rapeseed varieties in Huanggang and Xiangyang were compared through artificially simulated combined harvesting and two-stage harvesting. Results showed significant differences in the quality of rapeseed oil between the two harvesting methods. The red value (R-value), POV, total tocopherol contents, linoleic and linolenic acid content, and PTP content of the pressed rapeseed oil prepared by the combined harvesting method were about 27.6, 5.7, 15.8, 2.0, 0.5, and 28.6% lower than those of the oil produced from the two-stage harvesting method, respectively. Xiangyang and Huayouza62 performed better in the two regions and two varieties, respectively. To sum up, the rapeseed oil obtained 41–44 days after final flowering of combined harvesting, 35 days after final flowering, and six days of post-ripening of the two-stage harvesting had the best quality.

Monitoring the quality of fortified cold-pressed rapeseed oil in different storage conditions

Monitoring the quality of fortified cold-pressed rapeseed oil in different storage conditions

Physical and Chemical Characterisation of Conventional and Nano/Emulsions: Influence of Vegetable Oils from Different Origins.

The processes of oil production play an important role in defining the final physical and chemical properties of vegetable oils, which have an influence on the formation and characteristics of emulsions. The objective of this work was to investigate the correlations between oils’ physical and chemical properties with the stability of conventional emulsions (d > 200 nm) and nanoemulsions (d < 200 nm). Five vegetable oils obtained from different production processes and with high proportion of unsaturated fatty acids were studied. Extra virgin olive oil (EVOO), cold-pressed rapeseed oil (CPRO), refined olive oil (OO), refined rapeseed oil (RO) and refined sunflower oil (SO) were used in this study. The results showed that the physicochemical stability of emulsion was affected by fatty acid composition, the presence of antioxidants, free fatty acids and droplet size. There was a significant positive correlation (p < 0.05) between the fraction of unsaturated fatty acids and emulsion oxidative stability, where SO, OO and EVOO showed a significantly higher lipid oxidative stability compared to RO and CPRO emulsions. Nanoemulsions with a smaller droplet size showed better physical stability than conventional emulsions. However, there was not a significant correlation between the oxidative stability of emulsions, droplet size and antioxidant capacity of oils.

Effect of Deep Frying of Potatoes and Tofu on Thermo-Oxidative Changes of Cold Pressed Rapeseed Oil, Cold Pressed High Oleic Rapeseed Oil and Palm Olein.

One of the commonly used food preparation methods is frying. Fried food is admired by consumers due to its unique taste and texture. Deep frying is a process of dipping food in oil at high temperature, usually 170–190 °C, and it requires a relatively short time. The aim of this study was to analyze the thermo-oxidative changes occurring during the deep frying of products such as potatoes and tofu in cold pressed rapeseed oils and palm olein. Cold pressed rapeseed oil from hulled seeds (RO), cold pressed high oleic rapeseed oil from hulled seeds (HORO), and palm olein (PO) (for purposes of comparison) were used. Characterization of fresh oils (after purchase) and oils after 6, 12, and 18 h of deep frying process of a starch product (potatoes) and a protein product (tofu) was performed. The quality of oils was analyzed by determining peroxide value, acid value, p-anisidine value, content of carotenoid and chlorophyll pigments, polar compounds, smoke point, color (CIE L*a*b*), fatty acids content and profile, calculation of lipid nutritional quality indicators, and oxidative stability index (Rancimat). Cold pressed high oleic rapeseed oil was more stable during deep frying compared to cold pressed rapeseed oil, but much less stable than palm olein. In addition, more thermo-oxidative changes occurred in the tested oils when deep frying the starch product (potatoes) compared to the deep frying of the protein product (tofu).

Identification of volatile sulfur-containing compounds and the precursor of dimethyl sulfide in cold-pressed rapeseed oil by GC–SCD and UPLC–MS/MS

Volatile sulfur-containing compounds (VSCs) provide an important contribution to foods due to their special odors. In this study, VSCs in 21 cold-pressed rapeseed oils (CROs) from 9 regions in China were extracted and separated by headspace solid-phase microextraction combined with gas chromatography coupled with sulfur chemiluminescence detection. 19 VSCs were identified by authentic standards, and the total concentration of VSCs in all CROs ranged from 49.0 to 18129 μg/kg. Dimethyl sulfide (DMS), with its high odor activity value (7–14574), was the most significant aroma contributor to the CROs. Furthermore, S-methylmethionine (SMM) in rapeseed was first affirmed by ultra-performance liquid chromatography–tandem mass spectrometry and isotope quantitation. The positive correlation coefficient between DMS and SMM was 0.793 (p < 0.05), which confirmed SMM as a crucial precursor of DMS in CROs. This study provided a theoretical basis for selecting rapeseed materials by the distribution of essential VSCs and the source of DMS.

Effects of steam explosion pretreatment on the bioactive components and characteristics of rapeseed and rapeseed products

The objectives of this study were to obtain the optimal technical parameters of steam explosion for rapeseed and investigate the effects of pretreatment on the bioactive components and characteristics of three diverse samples of Brassica seed (Brassica napus, B. juncea and B. rapa) and their products. Under the optimal conditions, Brassica napus formed the largest amount of canolol, namely, 1210.10 mg/kg; B. rapa formed the smallest amount, namely, 82.70 mg/kg; and the canolol content was 2110.00 mg/kg in Brassica napus oil. Meanwhile, compared to the traditional cold-pressed rapeseed oil, the total tocopherol and phytosterol contents in Brassica napus, B. rapa and B. juncea oil increased by 5.3%, 4.8%, and 7.4% and 2.1%, 3.2%, and 5.1%, respectively. Steam explosion pretreatment also significantly affected the total phenolic contents and antioxidant capacities of the three types of rapeseeds and their processed products (P < 0.05). In addition, by steam explosion pretreatment, the EAA contents of B. rapa and B. juncea rapeseed cakes increased by 2.22% and 4.49%, respectively. These findings will provide data support and a reference basis for the application and development of steam explosion technology to rapeseeds of various types.

УЛУЧШЕНИЕ КАЧЕСТВ РАПСОВОГО МАСЛА ДЛЯ ИСПОЛЬЗОВАНИЯ В ДИЗЕЛЬНОМ ДВИГАТЕЛЕ

This article presents experimental studies on changing such chemical properties of vegetable (rapeseed) oil, such as viscosity, for its use as a fuel in diesel engines. With the help of hydrothermal technology, samples of vegetable oil were obtained and laboratory studies were carried out on a viscometer, which showed a decrease in viscosity up to 16%. Oil samples were obtained at different pressures up to 90 atm. and temperatures up to 130 C. All samples were passed through a liquid activator installed at the outlet of the reactor, which, due to spargers located in the path of the flow, provided the appearance of a gaseous and liquid mixture with an increased ability to mix and conduct chemical reactions. The reactor was a metal flask with a wall thickness of 10 mm, a volume of 6 liters, with installed temperature and pressure sensors, and a heating element for heating oil. The pressure was provided by a gear pump driven by a 3 kW electric motor. For the safety of testing, an automatic pressure and temperature regulator in the reactor, installed in the control panel, was developed. In order to compare with pure cold-pressed rapeseed oil, comparative tests were carried out on bench equipment of the laboratory, which showed the effectiveness of this technology and obtaining the characteristics of engine operation on rapeseed oil as close as possible to diesel fuel. During the research, quantitative indicators of the ingress of rapeseed oil into the engine crankcase were also determined. When using cold-pressed rapeseed oil, this figure after eight-hour tests at idle at different speeds was 3.21 liters. After the processing of rapeseed oil in the reactor and repeated tests, the oil in the engine crankcase was measured, where it was 1.92 liters, which was 60% of the previous experience

Differentiation between Aroma-Related Bioactives in Native Cold-Pressed Rapeseed Oils with Desired Sensory Attributes and with a Fusty/Musty Off-Flavor Using Multivariate Methods

A systematic quantitation of selected odorants using stable isotope dilution analysis (SIDA) was performed in six native cold-pressed rapeseed oils with desired retention of bioactives and desired sensorial attributes (“positive controls”, PCs), in nine native cold-pressed rapeseed oils eliciting a fusty/musty off-flavor (OFs), and in two rapeseed samples, from which two of the nine fusty/musty off-flavor oils were pressed. These data were used as basis to find marker compounds for the fusty/musty off-flavor by means of multivariate methods. Obtained data clustered pairwise in a heatmap clearly showed that all PCs and OFs were very similar to each other in their own group concerning the selected compounds. Additionally, data were statistically evaluated using principal component analysis (PCA). Based on selected compounds, a high accordance of PCs, in parallel to a clear discrimination to the group of fusty/musty off-flavor oils and to the two rapeseed samples, was achieved. In a biplot, compounds with the highest differences between the two oil groups were identified as 4-methylphenol, 3-methylbutanoic acid, 2-phenylethanol, 2-ethyl-3,6-dimethylpyrazine, and 2-methylbutanoic acid. Thus, these compounds can be seen as marker compounds for the fusty/musty off-flavor oils and the seeds and can, therefore, serve for quality control of the raw material within a quick routine method.

Front-Face Fluorescence Spectroscopy and Chemometrics for Quality Control of Cold-Pressed Rapeseed Oil During Storage.

The aim of this study was to test the usability of fluorescence spectroscopy to evaluate the stability of cold-pressed rapeseed oil during storage. Freshly-pressed rapeseed oil was stored in colorless and green glass bottles exposed to light, and in darkness for a period of 6 months. The quality deterioration of oils was evaluated on the basis of several chemical parameters (peroxide value, acid value, K232 and K270, polar compounds, tocopherols, carotenoids, pheophytins, oxygen concentration) and fluorescence. Parallel factor analysis (PARAFAC) of oil excitation-emission matrices revealed the presence of four fluorophores that showed different evolution throughout the storage period. The fluorescence study provided direct information about tocopherol and pheophytin degradation and revealed formation of a new fluorescent product. Principal component analysis (PCA) performed on analytical and fluorescence data showed that oxidation was more advanced in samples exposed to light due to the photo-induced processes; only a very minor effect of the bottle color was observed. Multiple linear regression (MLR) and partial least squares regression (PLSR) on the PARAFAC scores revealed a quantitative relationship between fluorescence and some of the chemical parameters.

Performance and emission characterization of a common-rail compression-ignition engine fuelled with ternary mixtures of rapeseed oil, pyrolytic oil and diesel

Biofuels are one of the short-term alternatives for reducing the well-to-wheel greenhouse gas footprint of transport. In the framework of compression-ignition engine fuels. This study investigates the feasibility of using cold-pressed rapeseed oil as a biocomponent, admixed with distilled tyre pyrolytic oil, as an energy-efficient alternative to commonly considered methyl ester-based mixtures in diesel fuel. Selected ternary and binary fuel blends are subjected to engine tests. Their scope covers 80% of the engine map and aims at identifying tradeoffs between fuel composition, engine performance and emissions. The results show that fuel mixtures containing a large fraction of rapeseed oil (up to 55% by volume) can be effectively combusted when pyrolytic oil distillate is introduced as the additive. The deterioration in brake efficiency for such fuel does not exceed 1.2% with respect to diesel baseline. At the same time, the results are superior in terms of both efficiency and emissions when compared to FAME-based biodiesel. Finally, with indicated efficiencies on a similar level as the diesel baseline, suggesting improved burning rate with pyrolytic oil addition, the study identifies parasitic losses in fuel injection equipment as a significant contributor to the overall efficiency penalty for the examined ternary mixtures.

The quality of cold-pressed rapeseed oil obtained from seeds of Brassica napus L. with increased moisture content [pdf

The quality of cold-pressed rapeseed oil obtained from seeds of Brassica napus L. with increased moisture content [pdf

The quality of cold-pressed rapeseed oil obtained from seeds of Brassica napus L. with increased moisture content.

The basic parameter influencing the quality of cold-pressed oil is the quality of seeds used&nbsp; for pressing. Adverse moisture content and storage temperature of rape seeds may affect the quality of oil obtained from them. This paper presents the effects of increased rapeseed moisture content on the quality of the oil pressed. The material used for the tests was rapeseed (canola) cv. PR 46 W14. The moisture content of the seeds was adjusted to 10%, 12% and 20%, and the seeds were stored at room temperature for 14 days. The samples were then dried to a seed moisture equal to 7% and oil was pressed from them. Acid and peroxide values, as well as the content of water, tocopherols and phenolic acids, were determined. In addition, a sensory analysis of the oil samples was carried out, and structural changes in the association colloids in the oil were determined using a fluorescent probe. With the increase in seed moisture, the increase in peroxide and acid values of the analyzed oils was recorded. A slight decrease in tocopherol content and a significant increase in phenolic acid concentration, depending on the seed moisture content, was observed. Sensory analysis showed odor sensory profile changes that probably indicate microflora development. The rapeseed moisture content has a crucial influence on the quality of oil obtained from them. Along with an increase in seed moisture, the possibility of developing undesirable microflora grows, which results in a deterioration in the quality of the obtained oil.