Unravelling the importance of seed roasting for oil quality by the non-targeted volatilomics and targeted metabolomics of cold-pressed false flax (Camelina sativa L.) oil and press cakes

False flax (Camelina sativa L.), known as camelina, is an ancient oil plant that has gathered renewed interest. In this study, a comprehensive analysis encompassing nontargeted volatilomics and targeted, quantitative metabolomics performed for cold-pressed oil and press cake and was integrated with sensory analysis of cold-pressed camelina oil and the effect of seed roasting was evaluated. Roasting in general resulted in the formation of 22 new volatile organic compounds (VOCs) in oil, while roasting at 140 and 180 °C resulted in the formation of 12 and 124 unique VOCs, respectively. Roasting notably influenced the profile of primary and secondary metabolites in both oil and press cakes, as well as volatilome and aroma of cold-pressed camelina oil. Many VOCs can be attributed to thermal degradation of primary and secondary metabolites. Roasting intensified the flavour of cold-pressed camelina oil, enhancing the perception of notes formed through the Maillard reaction.

Combining Targeted Metabolomics with Untargeted Volatilomics for Unraveling the Impact of Sprouting on the Volatiles and Aroma of False Flax (Camelina sativa) Cold-Pressed Oil

Sprouting of stored oilseeds due to improper storage can lead to quality defects of cold-pressed oils obtained from them. This study aimed to evaluate the effect of seed sprouting on volatile organic compounds (VOCs), aroma-active compounds, and the content of nonvolatile metabolites in cold-pressed false flax oil obtained from sprouted seeds. In this study, 88 unique VOCs were detected in sprouted oils, whereas only 42 were found in the control oils. The control oils were characterized by a higher abundance of alcohols, while all other groups of compounds were associated with sprouted seeds. The formation of many VOCs was reflected in changes in the nonvolatile precursors. Fifteen aroma-active compounds were identified in sprouted oil, with five compounds playing a significant role (FD ≥ 128) in aroma formation. The presented approach allowed identification of differences caused by seed sprouting, resulting in oils with a much stronger aroma and a richer profile of VOCs due to intensive metabolic changes. The origin of many VOCs can be explained by alterations in the content of nonvolatile metabolites.

Innovative insights into the roasting-driven transformation of volatile compounds and quality markers in flaxseed (Linum usitatissimum L.) oil

Roasting is essential for developing the characteristic aroma of flaxseed oil (FSO), yet its impact on oil quality remains underexplored. This study employed headspace-gas chromatography-mass spectrometry coupled with multivariate analysis to elucidate the dynamic changes in volatile compounds and quality characteristics of FSO subjected to varying roasting temperatures. Our findings revealed that seven key aroma compounds, identified through the variable importance in the projection scores of partial least square-discrimination analysis models and relative aroma activity value, served as molecular markers indicative of distinct roasting temperatures. These compounds included 2,5-dimethylpyrazine, 2-pentylfuran, (E)-2-pentenal, 2-ethyl-3,6-dimethylpyrazine, heptanal, octanal, and 2-hexenal. Notably, roasting at 200°C was found to enhance oil stability and antioxidant capacity, with phenolic compounds and Maillard reaction products playing synergistic roles in bolstering these qualities. Network analysis further uncovered significant correlations between these key aroma compounds and quality characteristics, offering novel perspectives for assessing FSO quality under diverse roasting conditions. This research not only enriched our understanding of the roasting process's impact on FSO but also provided valuable guidance for the optimization of industrial roasting practices. This study would provide important practical applications in aroma regulation and process optimization of flaxseed oil. .

Effect of Roasting on the Chemical Composition and Oxidative Stability of Tomato (Solanum lycopersicum L.) Seed Oil

In this study, tomato seed (TS) samples were subjected to different roasting conditions (90-170 °C and 10-30 min) to compare their effects on the chemical composition and oxidative stability of tomato seed oil (TSO). Unroasted TS was considered as a control sample. Our results revealed that moderate roasting (130 °C/20 min) can significantly increase the content of linoleic acid (54.01-54.89%), linolenic acid (2.17-2.41%), phytosterols (2789.56-3037.31 mg/kg), squalene (5.06-13.10 mg/kg), total phenols (22.37-22.67 mg GAE/100 g), and other functional components (p < 0.05) in TSO, while the antioxidant activity (via DPPH, ABTS, and FRAP assays) also increased. In addition, the tocopherol content decreased significantly (758.53-729.50 mg/kg). Accelerated oxidation experiments showed that roasting (170 °C/30 min) increased the oxidative stability index (OSI) of TSO from 5.35 to 7.07 h (p < 0.05). Furthermore, roasting gradually increased the content of 5-hydroxymethylfurfural (HMF) (0-1.74 mg/kg), which indicates that the oxidative stability and the degree of the Maillard reaction increased upon roasting. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) showed that moderate roasting (130 °C/20 min) improved the chemical composition, antioxidant activity, and oxidative stability of TSO. Furthermore, this work provides a useful theoretical basis for the processing and wide application of TSO in the pharmaceutical and food industries.

High-oleic rapeseed oil quality indicators and endogenous antioxidant substances under different processing methods

This study exposed high-oleic rapeseed oil (HORO) to different pretreatment (microwave or roasting) and processing methods to investigate (cold pressing, hexane extraction, subcritical butane extraction, and aqueous enzymatic extraction) the effects of processing technologies on HORO parameters associated with its physicochemical properties, endogenous antioxidant substances, and antioxidant capacity. The oil yield of various processing technologies was between 35.4% and 59.7%, and the fatty acid composition did not significantly differ. Hierarchical clustering and principal component analyses were used for evaluation. The results revealed that the microwave pretreatment-hexane extraction (M-HE) method resulted in significantly higher levels of tocopherols (688.4 mg/kg), polyphenols (1007.76 mg/kg), and phytosterols (1810.6 mg/kg) in HORO, implying strong free radical scavenging capacity (DPPH-oil: 79.63, DPPH-nonpolar: 71.42, DPPH-polar: 6.65, FRAP: 55.4, ABTS: 3043.7 μmol TE/kg). Hence, M-HE is a promising method for producing HORO with a higher stability and nutritional value.

Polyphenolic compounds from rapeseeds (Brassica napus L.): The major types, biofunctional roles, bioavailability, and the influences of rapeseed oil processing technologies on the content

The rapeseed (Brassica napus L.) are the important oil bearing material worldwide, which contain wide variety of bioactive components with polyphenolic compounds considered the most typical. The rapeseed polyphenols encompass different structural variants, and have been considered to have many bioactive functions, which are beneficial for the human health. Whereas, the rapeseed oil processing technologies affect their content and the biofunctional activities. The present review of the literature highlighted the major types of the rapeseed polyphenols, and summarized their biofunctional roles. The influences of rapeseed oil processing technologies on these polyphenols were also elucidated. Furthermore, the directions of the future studies for producing nutritional rapeseed oils preserved higher level of polyphenols were prospected. The rapeseed polyphenols are divided into the phenolic acids and polyphenolic tannins, both of which contained different subtypes. They are reported to have multiple biofunctional roles, thus showing outstanding health improvement effects. The rapeseed oil processing technologies have significant effects on both of the polyphenol content and activity. Some novel processing technologies, such as aqueous enzymatic extraction (AEE), subcritical or supercritical extraction showed advantages for producing rapeseed oil with higher level of polyphenols. The oil refining process involved heat or strong acid and alkali conditions affected their stability and activity, leading to the loss of polyphenols of the final products. Future efforts are encouraged to provide more clinic evidence for the practical applications of the rapeseed polyphenols, as well as optimizing the processing technologies for the green manufacturing of rapeseed oils.

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.

Characterization of New Egyptian Linseed Varieties and the Effects of Roasting on Their Pigments, Tocochromanols, Phytosterols, Omega-3 Fatty Acids, and Stability

The purpose of this study was to explore the effects of roasting linseeds on the pigment, lipid profile, bioactive components, and oxidative stability of the extracted oils. The linseed varieties Giza 11, Giza 12, Sakha 3, and Sakha 6 were roasted at 180 °C for 10 min, and the oils were extracted by cold pressing. The results showed that, after roasting, there was an increase in oil percentage and peroxide value, as well as small increases in p-anisidine and acid values. Roasting also caused an increase in chlorophyll content, while lutein and β-carotene tend to slightly decrease, except in the Giza 11 variety. The total phenolics content was markedly enhanced after roasting. Omega-3 fatty acids were not affected by the roasting process. The total amounts of tocochromanol were found to decrease in the Giza 12 and Sakha 6 varieties after roasting. Plastochromanol-8 increased in all varieties after roasting. The phytosterol composition was minimally affected by roasting. Roasting enhanced the stability of the extracted oils, increasing the induction period and decreasing EC50 values. These results may thus help to discriminate between the different linseed varieties and serve to recommend the use of roasting to enhance the oxidative stability of extracted oil.

ROS-Induced DNA-Damage and Autophagy in Oral Squamous Cell Carcinoma by Usnea barbata Oil Extract-An In Vitro Study

Oxidative stress is associated with aging, cancers, and numerous metabolic and chronic disorders, and phenolic compounds are well known for their health-promoting role due to their free-radical scavenging activity. These phytochemicals could also exhibit pro-oxidant effects. Due to its bioactive phenolic secondary metabolites, Usnea barbata (L.) Weber ex. F.H. Wigg (U. barbata) displays anticancer and antioxidant activities and has been used as a phytomedicine for thousands of years. The present work aims to analyze the properties of U. barbata extract in canola oil (UBO). The UBO cytotoxicity on oral squamous cell carcinoma (OSCC) CLS-354 cell line and blood cell cultures was explored through complex flow cytometry analyses regarding apoptosis, reactive oxygen species (ROS) levels, the enzymatic activity of caspase 3/7, cell cycle, nuclear shrinkage (NS), autophagy (A), and synthesis of deoxyribonucleic acid (DNA). All these studies were concomitantly performed on canola oil (CNO) to evidence the interaction of lichen metabolites with the constituents of this green solvent used for extraction. The obtained data evidenced that UBO inhibited CLS-354 oral cancer cell proliferation through ROS generation (316.67 × 10⁴), determining higher levels of nuclear shrinkage (40.12%), cell cycle arrest in G0/G1 (92.51%; G0 is the differentiation phase, while during G1 phase occurs preparation for cell division), DNA fragmentation (2.97%), and autophagy (62.98%) than in blood cells. At a substantially higher ROS level in blood cells (5250.00 × 10⁴), the processes that lead to cell death-NS (30.05%), cell cycle arrest in G0/G1 (86.30%), DNA fragmentation (0.72%), and autophagy (39.37%)-are considerably lower than in CLS-354 oral cancer cells. Our work reveals the ROS-mediated anticancer potential of UBO through DNA damage and autophagy. Moreover, the present study suggests that UBO pharmacological potential could result from the synergism between lichen secondary metabolites and canola oil phytoconstituents.

Free and Esterified Tocopherols, Tocotrienols and Other Extractable and Non-Extractable Tocochromanol-Related Molecules: Compendium of Knowledge, Future Perspectives and Recommendations for Chromatographic Techniques, Tools, and Approaches Used for Tocochromanol Determination

Free and esterified (bound) tocopherols, tocotrienols and other tocochromanol-related compounds, often referred to "tocols", are lipophilic antioxidants of great importance for health. For instance, α-tocopherol is the only tocochromanol with vitamin E activity, while tocotrienols have a positive impact on health and are proposed in the prevention and therapy of so-called modern diseases. Tocopherols, tocotrienols and plastochromanol-8 are the most well-known tocochromanols; in turn, knowledge about tocodienols, tocomonoenols, and other rare tocochromanol-related compounds is limited due to several challenges in analytical chemistry and/or low concentration in plant material. The presence of free, esterified, and non-extractable tocochromanols in plant material as well as their biological function, which may be of great scientific, agricultural and medicinal importance, is also poorly studied. Due to the lack of modern protocols as well as equipment and tools, for instance, techniques suitable for the efficient and simultaneous chromatographical separation of major and minor tocochromanols, the topic requires attention and new solutions, and/or standardization, and proper terminology. This review discusses the advantages and disadvantages of different chromatographic techniques, tools and approaches used for the separation and detection of different tocochromanols in plant material and foodstuffs. Sources of tocochromanols and procedures for obtaining different tocochromanol analytical standards are also described. Finally, future challenges are discussed and perspective green techniques for tocochromanol determination are proposed along with best practice recommendations. The present manuscript aims to present key aspects and protocols related to tocochromanol determination, correct identification, and the interpretation of obtained results.

Proximate Composition, Physicochemical, and Lipids Profiling and Elemental Profiling of Rapeseed (Brassica napus L.) and Sunflower (Helianthus annuus L.) Grown in Morocco

We investigate and compare the nutritional and physicochemical properties of rapeseed and sunflower grown in Morocco. In order to examine a complete physicochemical characterization, various parameters such as mineral profile, fatty acid composition, sterols contents, total flavonoids content (TFC), total polyphenols content (TPC), and quality oil parameters were evaluated. The results showed a relatively small difference in the physicochemical composition of the seeds, as sunflower seeds recorded higher amounts of protein and oil content (22.98 ± 0.01 g/100 g and 41.30 ± 0.50 g/100 g) than rapeseed (22.98 ± 0.01 and 38.80 ± 0.50), while mineral elements profile was observed to be statistically different. Nevertheless, both seeds were rich in K, Ca, P, Mg, and Na and they were relatively poor in Na, Fe, Mn, Cu, and Zn. The most represented macroelement was K with the amount of 7936.53 ± 63.87 mg/Kg in rapeseed and 7739.22 ± 59.50 mg/Kg in sunflower. On the other hand, Cu was present in the analyzed samples the least, mostly below 20 mg/kg. For TPC and TFC, the sunflower recorded higher values (49.73 ± 0.50 and 25.37 ± 0.39 mg GAE/g) than rapeseed (38.49 ± 0.24 and 22.55 ± 1.76 mg QE/g). The fatty acid composition showed that both extracted oils have beneficial proprieties, as they are rich in unsaturated fatty acids; namely, rapeseed oil contains a high level of oleic acid (C18 : 1) (62.19%), while sunflower oil was richer in linoleic acid (C18 : 2) (55.7%). As a result, we conclude that the studied varieties have major importance in terms of both nutritional and seed improvement potentials.

Individual and Joint Effect of Alpha-Tocopherol and Hydroxytyrosol Acetate on the Oxidation of Sunflower Oil Submitted to Oxidative Conditions: A Study by Proton Nuclear Magnetic Resonance

This study tackles the individual and joint effect of alpha-tocopherol and hydroxytyrosol acetate on the oxidation of sunflower oil submitted to accelerated storage conditions at intermediate temperature, in order to deepen the understanding of antioxidant–prooxidant behaviour. This was accomplished by ¹H Nuclear Magnetic Resonance. For this purpose, the evolution of the degradation of both the main components of the oil and the aforementioned added compounds was monitored by this technique throughout the storage time. Furthermore, the formation of a very large number of oxylipins and the evolution of their concentration up to a very advanced stage of oil oxidation, as well as the occurrence of lipolysis, were also simultaneously studied. The results obtained show very clearly and thoroughly that in the oxidation process of the oil enriched in binary mixtures, interactions occur between alpha-tocopherol and hydroxytyrosol acetate that notably reduce the antioxidant effect of the latter compound with the corresponding negative consequences that this entails. The methodology used here has proved to be very efficient to evaluate the antioxidant power of mixtures of compounds.

Antioxidant, Cytotoxic, and Rheological Properties of Canola Oil Extract of Usnea barbata (L.) Weber ex F.H. Wigg from Călimani Mountains, Romania

Usnea genus (Parmeliaceae, lichenized Ascomycetes) is a potent phytomedicine, due to phenolic secondary metabolites, with various pharmacological effects. Therefore, our study aimed to explore the antioxidant, cytotoxic, and rheological properties of Usnea barbata (L.) Weber ex F.H. Wigg (U. barbata) extract in canola oil (UBO) compared to cold-pressed canola seed oil (CNO), as a green solvent used for lichen extraction, which has phytoconstituents. The antiradical activity (AA) of UBO and CNO was investigated using UV-Vis spectrophotometry. Their cytotoxicity was examined in vivo through a brine shrimp lethality (BSL) test after Artemia salina (A. salina) larvae exposure for 6 h to previously emulsified UBO and CNO. The rheological properties of both oil samples (flow behavior, thixotropy, and temperature-dependent viscosity variation) were comparatively analyzed. The obtained results showed that UBO (IC₅₀ = 0.942 ± 0.004 mg/mL) had a higher 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity than CNO (IC₅₀ = 1.361 ± 0.008 mg/mL). Both UBO and CNO emulsions induced different and progressive morphological changes to A. salina larvae, incompatible with their survival; UBO cytotoxicity was higher than that of CNO. Finally, in the temperature range of 32-37 °C, the UBO and CNO viscosity and viscoelastic behavior indicated a clear weakening of the intermolecular bond when temperature increases, leading to a more liquid state, appropriate for possible pharmaceutical formulations. All quantified parameters were highly intercorrelated. Moreover, their significant correlation with trace/heavy minerals and phenolic compounds can be observed. All data obtained also suggest a possible synergism between lichen secondary metabolites, minerals, and canola oil phytoconstituents.

A chemometrics approach comparing characteristics and free radical scavenging capacity of flax (Linum usitatissimum L.) oils obtained from seeds and cakes with different extraction methods

BACKGROUND

Flax oil, a nutritive vegetable oil, is a rich natural source of the essential C18:3 α-linolenic acid and trace nutrients (tocopherol, phytosterol, polyphenol, flavonoid, etc.). In most small- and medium-sized facilities, the oil content in pressed cake is as high as 10%, which is not fully extracted and utilized. These cannot be neglected since they account for a considerable proportion. Characteristics and free radical scavenging capacity of flax (Linum usitatissimum L.) oil obtained from seeds and cakes with different extraction methods - cold-pressing, hot-pressing (120 and 160 °C) and solvent extraction (oil extracted with solvent from flaxseed, cold-pressed cake, and hot-pressed cake) - were evaluated and analyzed using chemometrics methods.

RESULTS

The composition of C18:3 α-linolenic acid of flax oil was not affected by the extraction methods in this work. Flax oils extracted with solvent from pressed cakes had lower content of bioactive minor components (tocopherols and phytosterols) compared with pressed and solvent-extracted seed oils. The former also showed poorer oxidative stability and free radical scavenging capacity (polar fraction) when compared with the latter. Flax oils could be distinguished with principal component analysis and hierarchical cluster analysis. Tocopherols and phytosterols exhibited significant contributions to the antioxidant capacity of flax oils via correlation analysis and multiple linear regression analysis.

CONCLUSION

Tocopherols and phytosterols were appropriate and potent indicators for evaluating the antioxidant capacity of flax oil. Results have important implications for the industrial production and nutritional value of flax oil, especially for flax oils from the cakes after pressing. © 2021 Society of Chemical Industry.

Air frying pretreatment and the recovery of lipophilic sinapates from the oil fraction of mustard samples

Roasting of mustard seeds prior to oil extraction is a well-documented unit operation essential to produce canolol and other lipophilic sinapates. This study investigated the effectiveness of air frying as a seed roasting treatment operation for enhancing the recovery of lipophilic sinapates from various mustard samples and fractions/products. Air frying of seeds, powder, cake, bran, and flour from different mustard varieties was carried out at temperature-time combinations of 160, 170, and 180°C for 5, 10, 15, and 20 min, respectively. Oil was extracted using the Soxtec method. Lipophilic sinapates were extracted from the oil using equal volumes of hexane to methanol 70% (v/v) and quantified by high performance liquid chromatography-diode array detection (HPLC-DAD). The total phenolic content (TPC) and antioxidant activity of the oils were also evaluated. The results showed a time-temperature dependency for the recovery of major oil-soluble sinapates in all mustard samples and fractions. The optimum air frying condition 180°C for 15 min produced the maximum yield of canolol as well as other unidentified oil-soluble sinapates (retention time (RT)-7.7, RT-11.50, RT-14.95, and RT-16.24 min). The oil from lower grade yellow mustard seeds (LGYMS) roasted at 180°C for 20 mins specifically had the highest TPC (3402.22 ± 58.79 mg GAE/g oil), while LGYMS oils generally showed better antioxidant activities (2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric ion reducing antioxidant power (FRAP), and inhibition of linoleic acid oxidation) but were lower in metal ion chelating capacity. This information would be beneficial to the oil industry because air frying generated valuable canolol and other antioxidant lipophilic sinapates from mustard varieties and their fractions. PRACTICAL APPLICATION: A major limitation in the application of natural extracts in vegetable oils is the poor lipophilic nature of phenolic compounds. This study employed a new thermal treatment (air frying) in the recovery of canolol and other lipophilic antioxidants. Such treatments can enrich mustard-based ingredients with canolol and other lipophilic antioxidants for domestic and industrial applications.

Rapidoxy® 100: A Solvent-Free Pre-treatment for Production of Canolol

RapidOxy® 100 is an automated instrument originally designed for measuring the oxidative stability of both solid and liquid samples. The compact and portable design of RapidOxy® 100, and its built-in pressurized heating chamber, provides a suitable environment for studying processing conditions. The feasibility of using oxygen or an inert atmosphere provides the ideal environment to study the effect of dry heat pre-treatment on canola antioxidants. The current study used RapidOxy® 100 to examine the impact of pressurized dry heat pre-treatment, under nitrogen, on the ultrasonic extraction of phenolic compounds. The effect of different pre-treatment temperature-time combinations of 120, 140, 160, and 180°C for 2, 5, 10, 15, and 20 min on the subsequent extraction of canola phenolic compounds was examined. The major sinapates identified by HPLC were sinapine, sinapic acid, and canolol. The optimum RapidOxy® condition for the maximum recovery of canolol was 160°C for 10 min. RapidOxy® 100 proved to be a novel and versatile instrument for enhancing the extraction of phenolic compounds.

Effect of infrared ray roasting on oxidation stability and flavor of virgin rapeseed oils

Effects of infrared ray roasting (IRR) on the oxidation stability and flavors of virgin rapeseed oil (VROs) at 110-170°C were investigated and compared with traditional roller roasting (TRR). Results showed that IRR samples showed lower acid and peroxides values, higher oxidation stability index, and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity than TRR ones. IRR samples displayed better thermal expansion of rapeseed for internal fragmentation from microstructures, which facilitated the release of tocophenols (652.63-748.78 mg/kg) and 4-vinylsyringol (7.54-678.19 mg/kg), compared with TRR ones with tocophenols (652.63-689.28 mg/kg) and 4-vinylsyringol (7.54-524.18 mg/kg) contributing to better oxidation stability. Moreover, important volatile compounds, including pyrazines, isothiocyanates, nitriles and aldehydes, were formed quantitatively more in IRR than TRR samples, which was attributed to better heat transfer efficiency and internal fragmentation promoting complex reactions inside rapeseed. Therefore, IRR has more positive roasting effects on VROs than TRR. PRACTICAL APPLICATION: Virgin rapeseed oil is a massively consumed flavor vegetable oil, but the traditional high-temperature roller seed roasting process can cause serious quality problems. Our work applied a novel roasting technology, infrared ray roasting to rapeseed pretreatment. The results show that this new type of roasting technology is more efficient and stable and has important applications in the production of virgin rapeseed oil with better oxidative stability and flavor.

Antioxidant interaction of α-tocopherol, γ-oryzanol and phytosterol in rice bran oil

In this study, purified rice bran oil (RBO) was used as a lipid matrix model to study the individual and binary antioxidant capacity of the minor constituents (α-tocopherol, γ-oryzanol and phytosterol) added at different concentrations and ratios. The results revealed that concentration influenced on the oxidation stability and scavenging capacity, while ratio mainly affected the type of interaction or the degree of synergism or antagonism. It was important to notice that the antioxidant capacity of α-tocopherol would decrease under high concentration. Besides, the inhibition of phytosterol on α-tocopherol and the formation of hydrogen bond between γ-oryzanol and phytosterol were speculated by the interactions of these minor constituents. This work helps to select efficient combinations for stabilizing the anti-oxidation of nutrient enriched RBO or provide suggestions for moderate retain of minor constituents in RBO.

Nutritional quality and phytochemical contents of cold pressed oil obtained from chia, milk thistle, nigella, and white and black poppy seeds

Cold pressed oils obtained from chia (Salvia hispanica L.), milk thistle (Silybum marianum L.), nigella (Nigella sativa L.), and white and black varieties of poppy (Papaver somniferum L.) seeds were character­ized. The nutritional quality was determined based on the analysis of fatty acids, tocochromanol and phytos­terol contents, as well as antioxidant activity and general physico-chemical properties. Among the oils analyzed the fatty acid composition most beneficial for health was found in chia seed oil, with 65.62% of α-linolenic acid and the n-6:n-3 fatty acid ratio of 1:3.5. Other oils studied were rich sources of linoleic acid (18.35-74.70%). Chia seed oil was also distinguished by high contents of phytosterols, mainly β-sitosterol (2160.17 mg/kg oil). The highest content of tocochromanols was found in milk thistle oil with dominant α-tocopherol (530.2 mg/kg oil). In contrast, the highest antioxidant activity was recorded for nigella oil (10.23 μM Trolox/g), which indi­cated that, in addition to tocopherols, other antioxidants influenced its antioxidant potential.

The effect of drying on the native tocopherol and phytosterol content of Sinapis alba L. seeds

BACKGROUND

Postharvest processing, including drying, has a significant effect on the processability of oil crop seeds. High drying air temperature may significantly affect the levels of bioactive compounds in plant raw materials. We decided to investigate the subject given the lack of data on the drying of mustard seeds. The aim was to determine the effect of drying temperature on free fatty acid, phytosterol and tocopherol levels in the oil obtained from white mustard seeds. Seeds were dried in a thin layer at 40, 60, 80, 100, 120 and 140 °C. Changes in phytosterol levels were assessed using gas chromatography-mass spectrometry and changes in tocopherol levels by high-performance liquid chromatography.

RESULTS

The analysis showed that, upon completion of air drying at 40-100 °C, losses of sterols did not exceed 5%, while upon completion of drying at 120 °C and 140 °C these losses amounted to 17-50%. Our investigation also showed that during drying of white mustard seed the total tocopherol levels increased, and the higher the drying temperature, the greater the increment. In seeds air-dried at 120 °C and 140 °C, the increase in tocopherol amounted to 7-9%.

CONCLUSION

We also showed that the temperature of the drying agent significantly affects the tocopherol and phytosterol levels. It was found that a maximum temperature of 100 °C provides optimal drying conditions for mustard seeds. Principal component analysis identified two subgroups of oils obtained from seeds dried at 120 °C and 140 °C, which differed considerably from the other samples in terms of their bioactive component contents. © 2019 Society of Chemical Industry.

Degradation of Tocopherol Molecules and Its Impact on the Polymerization of Triacylglycerols during Heat Treatment of Oil

The aim of the study was to analyze the influence of the surface area to volume ratio of pressed and refined rapeseed oils on the changes in tocopherol content and polymerization of triacylglycerols during heating. In the study the pressed and refined rapeseed oil was heated at 170 °C, during 6, 12, and 18 h with three different surface area to volume (s/v) ratios (0.378, 0.189, and 0.126 cm-1). During heating, a decrease in tocopherols and increases in dimers, trimers, and oligomers of triacylglycerols were observed. However, the changes were dependent on the surface area to volume ratio used, type of oil and time of heating. The biggest changes were observed in oil with the biggest s/v ratio (0.378 cm-1), and the lowest when the s/v ratio was 0.126 cm-1. The pressed oil was characterized by faster degradation of tocopherols and slower increase of triacylglycerol polymer levels compared to refined oil.

Seed-Roasting Process Affects Oxidative Stability of Cold-Pressed Oils

The oxidative stability of vegetable oils mainly depends on their fatty acid composition, their degree of unsaturation, and the presence of compounds with antioxidant activity. This paper reports on the effects of the process of roasting oil seeds, prior to pressing them, on the basic characteristics of the oils produced and their oxidative stability. The differential scanning calorimetry (DSC) technique was used to study the process of oxidation of the oil samples in an oxygen-flow cell. Chromatographic analysis revealed that roasting the seeds increased the levels of chlorophyll and β-carotene in all the cold-pressed oils. Similar results were observed for the oil's antioxidant activity, measured by the scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical method. Our results also indicated that roasting seeds prior to pressing them for oil had a positive effect on the oil's stability, as determined by the DSC method. This manifested in both the extension of oxidation induction time and the final oxidation time.

Changes in oxidative stability and protein profile of flaxseeds resulting from thermal pre-treatment

BACKGROUND

The oxidative stability of oilseeds is crucial for their technological/nutritional quality and shelf life. This research aimed to evaluate the effect of thermal pre-treatment (steaming and roasting under various time/temperature conditions) on flaxseed oil and protein stability. The monitoring of changes in oil oxidation in situ and protein profiles (SDS-PAGE) and analysis of the antiradical activity of ethanolic and aqueous fractions were included in the study.

RESULTS

Flaxseed stability during storage was considerably affected by thermal pre-treatment conditions. Dynamics of oil oxidation was accelerated at 160 °C and 180 °C but slowed at 200 °C. Influence of pre-treatment conditions on the antiradical activity of the aqueous fraction was clearly observed and no effect concerning the ethanolic fraction was found. The most significant changes in protein profile of 200 °C-roasted flaxseed were found with the observed disappearance of 19 kDa protein. A treatment-dependent decrease in the 13 kDa protein was also detected. Based on the aqueous extract protein profiles, roasting conditions were found to be crucial for protein extractability.

CONCLUSIONS

The study has broadened knowledge of the consequences of flaxseed thermal treatment. The deterioration of flaxseed oil oxidative stability is shown. The changes of 19 and 13 kDa proteins suggest their sensitivity to thermally induced aggregation and/or cross-link. © 2018 Society of Chemical Industry.

The effect of microwave pre-treatment of rapeseed on the degradation kinetics of lipophilic bioactive compounds of the oil during storage

This study examined the storage stability of tocochromanols and carotenoids in the oils prepared from microwave pre-treated (MV) rapeseeds (2-10 min, 800W) during storage at 20 °C for 12 months. In line with lipophilic antioxidant degradation throughout the storage period, changes in the antioxidant capacity of the oil were monitored. Microwaving significantly affected the concentration of lipophilic antioxidants in the oil. After 10 min of MV pre-treatment the highest content of total tocochromanols (76.64 mg/100g) was achieved, whereas a maximum carotenoid concentration (861.28 μg/100g) was obtained following 6 min seed MV pre-treatment. The degradation kinetics for the tocochromanols and carotenoids followed a zero-order kinetic model. From the kinetic analysis, it was shown that the degradation rate constant (k) of both tocochromanols and carotenoids decreased with longer seed exposure to MV radiation. The kinetics of antioxidant capacity degradation during the storage of oils followed a zero-order reaction. The rate of antioxidant capacity degradation in the control oil was higher (k=9.1 x 10-2 mmol TEAC/l/month) compared with oils prepared from MV pre-treated seeds (k=6.8-8.0 x 10-2 mmol TEAC/l/month).

Effect of pretreatment on the proximate composition, physicochemical characteristics and stability of

The present research work was intended to study the influence of roasting and germination of the kernel seeds of Sudanese Moringa peregrina on the physicochemical characteristics and the oxidative stability of the extracted oil. Roasting was carried out at 180 ˚C for 25 minutes, whereas germination was done at ambient conditions in a wet jute bag for 5–7 days. The oil was extracted using n-hexane in a Soxhlet extraction apparatus. The results show that the oil contains α-tocopherols (152mg/kg) and oleic acid (above 70%) as the major tocols and fatty acids, respectively. Germination reduced the peroxide value and increased the acid value in a significant way (p < 0.05) whereas the opposite trend was noticed in the case of roasting. It is crucial to note that, with the exception of the acid value of the germinated sample, peroxide and acid values remained below one meq O2/Kg of oil and one mg KOH/g of oil, respectively. The oxidative stability of the oil from the roasted sample was increased almost by 80% compared to the raw one. Roasting of the kernels prior to oil extraction is imperative for improving its oxidation resistance and the physicochemical characteristics.

Dehulling and microwave pretreatment effects on the physicochemical composition and antioxidant capacity of virgin rapeseed oil

The effect of microwave heating (800 W) of whole and dehulled rapeseeds for 2 to 8 min was investigated in order to evaluate the impact of dehulling in conjunction with microwaving on the nutritional value, antioxidant activity and physicochemical properties of virgin rapeseed oil. Control oil produced from dehulled seeds (DRO) had higher amounts of bioactive compounds, such as tocochromanols and phytosterols, lower content of pigments, and higher content of primary and secondary oxidation products compared to oil pressed from whole seeds (WRO). Oils pressed from seeds that had previously undergone thermal treatment demonstrated gradual increase of oxidative stability, radical scavenging activity, moreover microwave treatment to caused darkening of oil, assessed in terms of changes in L*a*b* coordinates as well as browning index. Thermally-induced compositional changes were seen mainly in canolol, phytosterols, and carotenoids content, while only slight increase of tocopherols and phenolics was observed. The most pronounced effect of microwave pretreatment was noted for canolol formation-for 8-min MV exposure canolol quantity was approximately 7- and 23-fold higher, in comparison with control WRO and DRO samples, respectively (increase from 61.39 to 456.04 µg/g, and from 13.39 to 320.44 µg/g).

Mechanical hulling and thermal pre-treatment effects on rapeseed oil antioxidant capacity and related lipophilic and hydrophilic bioactive compounds

In this study, the effect of rapeseed mechanical hulling and thermal pre-treatment by microwaves (from 2 to 10 min with 2-min intervals, 800 W) and roasting (from 20 to 100 min with 20-min intervals, 165 °C) on the content of phytochemicals in the oil was investigated. Results showed that both pre-treatments applied differentiated the oils in terms of the content of bioactive compounds. In general, oils pressed from hulled and thermally pre-treated seeds contained higher content of tocopherols, PC-8 and phytosterols, while oils pressed from non-hulled and pre-processed seeds had significantly higher concentration of polyphenols. Both microwaving and roasting contributed to an increase of antioxidant capacity of studied oils. The increase of radical scavenging activity of oils was seen mainly in hydrophilic fraction of oil, which was highly positively correlated with the amount of canolol formed during seeds heating.