Search

The nutritional quality and sensory properties of virgin olive oils (VOO) are strongly influenced by a complex endogenous enzyme system. The activity of these enzymes can be influenced by the process conditions during oil production. The aim of the present study was to determine the influence of flash thermal treatment (FTT) on lipoxygenase activity and on the formation of volatile compounds. Olive fruits from Istarska bjelica and Levantinka were used for this experiment. FTT was performed as a pretreatment to malaxation by rapid cooling or heating from 15 to 40 °C. Lipoxygenase was isolated from the olive paste after malaxation, and its activity was determined by measuring the concentration of hydroperoxides formed by the HPLC method. The volatile compounds of VOOs were analyzed by SPME - GC/MS. The results show that lipoxygenase activity is cultivar dependent, with Levantinka having significantly higher activity. Consequently, Levantinka VOOs have significantly higher concentrations of lipoxygenase pathway volatile compounds. FTT had no significant effect on lipoxygenase activity, although the trend of decreasing activity with increasing temperature was observed. However, volatile compounds of the produced oils were temperature dependent, and their concentration increases from 15 °C to 20 °C for Levantinka and to 25 °C for Istarska bjelica. Thereafter, it gradually decreases with increasing temperature. The concentration of secondary oxidation products was also determined to determine the influence of the temperature on the oxidation processes. Neither the cultivar nor the FTT had any effect on the oxidation products.

Plant proteins are receiving a lot of attention due to their abundance in nature, customizable properties, biodegradability, biocompatibility, and bioactivity. As a result of global sustainability concerns, the availability of novel plant protein sources is rapidly growing, while the extensively studied ones are derived from byproducts of major agro-industrial crops. Owing to their beneficial properties, a significant effort is being made to investigate plant proteins’ application in biomedicine, such as making fibrous materials for wound healing, controlled drug release, and tissue regeneration. Electrospinning technology is a versatile platform for creating nanofibrous materials fabricated from biopolymers that can be modified and functionalized for various purposes. This review focuses on recent advancements and promising directions for further research of an electrospun plant protein-based system. The article highlights examples of zein, soy, and wheat proteins to illustrate their electrospinning feasibility and biomedical potential. Similar assessments with proteins from less-represented plant sources, such as canola, pea, taro, and amaranth, are also described.

Endogenous olive enzymes represent a crucial link between fruit composition and the nutritional and sensory characteristics of virgin olive oil. Enzymes such as β-glucosidase, polyphenol oxidase and peroxidase influence the content and composition of polyphenols, the main antioxidants in virgin olive oils. Lipoxygenase and hydroperoxide lyase convert fatty acids into volatile components responsible for the specific sensory properties of the oil. The aim of the present study was to determine the influence of fruit ripeness on the enzymatic activity of β-glucosidase, polyphenol oxidase, peroxidase and lipoxygenase in four Croatian autochthonous olive cultivars. For this experiment, olive fruits from two Dalmatian (Oblica and Levantinka) and two Istrian cultivars (Rosulja and Istarska bjelica) grown in their area of origin were harvested on three different harvest dates, from October 28 to November 9, 2021. The β-glucosidase, polyphenol oxidase and peroxidase were isolated from the acetone powder of the paste. The activity of these enzymes was determined spectrophotometrically, and the formation of p-nitrophenol from p-nitrophenyl glucopyranoside was measured for β-glucosidase, the formation of o-quinone from catechol for polyphenol oxidase, and the formation of tetraguaiacol from guaiacol for peroxidase. Lipoxygenase was isolated directly from olive paste, and its activity was determined by measuring the concentration of formed hydroperoxides by HPLC. The activity of β-glucosidase was detected only in a few samples, which was not sufficient to determine the influence of the factors studied on its activity. Polyphenol oxidase activity increased between the first and second harvest dates, and this increase was significantly higher in the Istrian cultivars. At later harvest dates, the activity decreased, but to a greater extent in the Dalmatian varieties. Peroxidase activity was significantly affected by both ripening and cultivar. Istrian cultivars had significantly higher peroxidase activity than Dalmatian cultivars. The activity was lower in riper fruits, with the exception of Levantinka, which had the highest activity in ripe fruits. Lipoxygenase activity was influenced primarily by harvest date: on the first date, activity was highest in Rosulja and Levantinka, on the second date in Istarska bjelica, and on the third date in Oblica. Throughout the harvest period, lipoxygenase activity was higher in Rosulja and Levantinka than in the other two cultivars.

Innovative technologies are being widely studied for their application in the production of virgin olive oil. Flash thermal treatment is one of these techniques, since the regulation of temperature allows control over complex enzyme systems that affect the nutritional value, oxidative stability and sensory profile of virgin olive oil [1-3]. The aim of this study was to determine the effects of flash thermal treatment (both cooling and heating) on the antioxidant activity of virgin olive oil from four different varieties (Oblica, Rosulja, Istarska bijelica and Levantinka). Flash thermal treatment was applied at 6 different temperatures in the range of 15-40 °C. It was used as a malaxation pretreatment for the production of virgin olive oil on a laboratory scale using the Abencor system. The antioxidant activity of the produced oils was determined using the DPPH method previously described by Kraljić et al [4]. The results show a significant influence of the variety and pretreatment on the antioxidant activity of virgin olive oil, as well as their interaction. Rosulja had the highest antioxidant activity (90.8% on average) compared to the other three varieties (84.3, 75.6 and 74.8% for Oblica, Istarska bijelica and Levantinka, respectively). In relation to the applied flash thermal treatment, Oblica, Rosulja and Levantinka showed significantly higher antioxidant activity at the highest temperature (40 °C), while Istarska bijelica responded better to mild temperatures (20-30 °C).

The oxidative stability of fats and oils is a crucial parameter that determines the shelf life of a product, but also the general use of the fats and oils. Differential scanning calorimetry (DSC) is a promising new technique that is fast, reliable and uses the exothermic character of the oxidation reaction to determine the induction time (in the isothermal DSC method) or the induction temperature (in the non-isothermal, i.e., dynamic DSC method). The objective of the present study was to optimize the conditions of the DSC method to determine the oxidative stability of virgin olive oil. Both the isothermal and dynamic methods were developed on a 214 Polyma DSC (NETZSCH-Gerätebau GmbH) and optimized using extra virgin olive oil from the Croatian market. The parameters studied were sample size (4, 8 and 12 mg), sample preparation (use of an open or a sealed pan with a pinhole), temperature (130, 140 and 150 °C) for the isothermal method and heating rate (5, 10, 15 and 20 °C/min) for the dynamic method. The results show that the DSC method is a reliable method for determining oxidation stability for both isothermal and non-isothermal methods. Sample size did not affect induction time, but a smaller portion size resulted in better reproducibility of the results. Regarding sample preparation, there was no statistical difference between results obtained with an open or sealed aluminum pan. However, it is better to use a hermetically sealed pan with a pinhole to protect the instrument from possible contamination. The induction time at 130 °C was 287 minutes, which was considered unacceptable, while a temperature of 140 °C proved to be optimal. A temperature of 150 °C also showed satisfactory reproducibility of results, but a longer induction time at 140 °C makes it easier to track changes between different oils or during storage. For the determination of the induction temperature (dynamic DSC), a heating rate of 15 °C/min proved to be optimal. Although repeatable results were also obtained with a heating rate of 10 °C/min, the use of a higher temperature rate can significantly speed up the analysis. The other two heating rates were considered unsuitable due to the lack of reproducibility.

The health benefits of the Mediterranean diet have been associated with the consumption of extra virgin olive oil (EVOO) as the main source of fats. Nowadays, the usage of EVOO as cooking oil to prepare meals is highly recommended. During heating, the oil undergoes several chemical reactions that influence its chemical composition and quality. Therefore, this study aimed to investigate the influence of heating on quality parameters, phenolic and volatile compounds in Leccino, Istarska bjelica, and Buža monovarietal EVOO. The oil samples were submitted to heating in an air oven at two different temperatures (180 °C and 220 °C), simulating usual roasting conditions typical for Mediterranean cuisine. Fresh, unheated oil was used as a control. Quality parameters related to oxidation status of oil, peroxide value, and spectrophotometric indices (K232, K268, and ΔK) were determined according to the analytical methods described in the European Commission Regulation from 1991, amendments included. The composition of phenolic compounds was determined by HPLCDAD, and volatiles’ profiles using SPME and GC-FID techniques. Significant losses in oxidative stability and decrease in phenolic and volatile compounds were more pronounced at higher heating temperatures, which underlined the temperature dependency of oxidative degradation during cooking conditions. However, there was still a considerable amount of phenolic compounds preserved after heating. In addition to quality parameters that served as oxidation indicators, hydroxytyrosol acetate among phenolic compounds and octanal, (E)- 2-octenal, hexanal, 3-pentanone, and 1-penten-3- one among volatiles, were underlined as possible thermal oxidation markers. Aside from being influenced by the heating temperature, the changes in the phenolic composition were cultivar dependent, while the changes in the composition of volatile compounds were found to be caused primarily by the heating temperature with no significant influence of the cultivar as an investigated factor. The obtained results contribute to the understanding of changes in quality and composition of Croatian monovarietal EVOO after heating, as well as provide new insights on the preservation of bioactive compounds in the course of the cooking process. Acknowledgement: This work has been supported by the Croatian Science Foundation under the project “Young researchers' career development project – training of new doctoral students”, DOK-2018-09-2293.

Aim: Pulsed electric field (PEF) is an emerging new technology that is finding more and more applications in the food sector. Virgin olive oil is no exception, as its application can significantly increase oil yield. However, changes in the chemical composition of virgin olive oil vary from study to study. This could be due to the fact that the chemical composition of the oil is directly influenced by the endogenous enzymes of the olive fruit responsible for the distribution of polyphenols in virgin olive oil and its sensory properties. Therefore, the aim of this study was to determine the effect of PEF on endogenous olive enzymes in model systems. Methods: Model systems of commercial enzymes (β-glucosidase and lipoxygenase) and their substrates (p- nitropheniygluco-pyranoside and linoleic fatty acid, respectively) were treated with HVG60/1 PEF (Impel, Zagreb, Croatia) for 1, 2, and 5 min with voltages of 0.1 and 0.5 kV/cm2 and a frequency of 25 and 125 Hz. Then, the treated enzyme/substrate solution was incubated at 25°C for 30 minutes to simulate a malaxation process. The activities of the enzymes were determined spectrophotometrically. Results: The activity of PEF-treated enzymes increased 4.5- fold for β-glucosidase and 2-fold for lipoxygenase compared to the untreated enzymes. The β- glucosidase activity measured immediately after PEF treatment was significantly affected by all factors and also by the interaction of voltage and time and frequency and time. Higher voltage resulted in an increase in β-glucosidase activity with longer treatment duration. After an additional 30-min incubation at 25 °C, β- glucosidase activity was affected only by PEF voltage, whereas it increased with higher voltage. Immediately after PEF treatment, lipoxygenase activity for linoleic fatty acid was significantly affected by treatment duration, with longer PEF treatments increasing activity. However, after incubation, longer treatment time resulted in lower amounts of hydroperoxides produced, which might be related to their spontaneous degradation. Conclusion: The introduction of PEF in virgin olive production as a pretreatment of malaxation could lead to a higher concentration of phenols and an improvement of the sensory characteristics of the oil due to an increased enzymatic activity.

Olive pomace, a by-product of the olive oil production, represents a serious ecological problem in Mediterranean region. Olive pomace is a dark-coloured waste that contains high amounts of organic materials that are not easily degradable or can even be toxic to plant life. But some of these compounds, like phenolic compounds, can act as potent natural antioxidants with bioactive activities. Olive pomace is a great source of phenolic alcohols, phenolic acids, flavonoids, lignans and especially secoiridoids, specific phenolic compounds of the Oleaceae family plants. The removal of the phenolics can facilitate further processing of the pomace and extracted compounds could be used as antioxidants in different food systems or as nutraceuticals. Nowadays new technologies and new generation of solvents are investigated in order to reduce environmental impact by increasing efficiency and sustainability of the extraction process. That is why the aim of this research was optimization of the method for the extraction of phenolic compounds from olive pomace using natural deep eutectic solvents and microwaves and/or ultrasound. We tested several green solvents with choline chloride or betaine chloride as hydrogen acceptor and various hydrogen-bond donors (sugars, alcohols ad carboxylic acids). Of eighth different natural deep eutectic solvents tested in our research, choline citrate was found to be most effective. Selected solvent was further used for the optimization of extraction process using and an ultrasonic-microwave cooperative reactor. Results have showed that microwave assisted extraction is the method of choice for the isolation of phenolic compounds from olive pomace. Longer extraction time and higher power used have positive impact on the extractability. Optimal extraction parameters are 30% water in the solvent, 12 minutes extraction time, and microwave power 300 W. Using microwave assisted extraction of phenolic compounds with selected parameters resulted in reduction of extraction time by 92% and increase of phenolic yield for 28% when compared to conventional methanol extraction method.

Nutritional value of flaxseed could be singled out in three major compounds: oil with dominant alpha linolenic fatty acid, fibers and polyphenols in form of glucosides, mostly lignans. Quantity of lignans in flaxseed is far greater than any other natural source but during oil extraction process polyphenols are left in press cake which is rarely used for human consumption. Lignans show significant biological activity through their derivates formed in our gut by intestinal bacteria. Apart from lignans, other detected phenols in flaxseed include ferulic and p-coumaric acid glucosides. Current methods of polyphenol extraction from flaxseed are time consuming (6h or more) and use organic solvents which mixed with NaOH which have negative impact on an environment. Deep eutectic solvents (DES) present inexpensive and ecological alternative to organic solvents while their role will be attractive not only for academic and medicinal research but also for industrial research. Combination of microwave and ultrasound extraction with deep eutectic solvents replacing organic solvents opens new possibilities in significantly improving this process. In this research, we tried to replace organic solvents with different DES and compare the results with some standard methods. Four different DES mixtures with alkaline properties were used for extraction: choline chloride:urea:glycerol, choline chloride:ethylene glycol, choline chloride:urea:ethylene glycol and choline chloride:urea with different 0.1 M NaOH ratios. Combination of microwave and ultrasound extraction showed better results compared just with microwaves while higher NaOH ratios (from 30 up to 50 %) had significant influence on quantity of extracted polyphenols. Much better results were obtained with ferulic and p- coumaric acid glucosides then with lignans. Up to 50 % of them were extracted compared with standard methods while lignan recovery was closer to 20 %. While this method needs further improvement and optimization the most promising solvents are choline chloride:urea:glycerol and choline chloride:ethylene glycol with 40 % of 0.1 M NaOH, extraction time of 6 minutes and microwave power 200W for choline chloride:urea:glycerol and extraction time of 9 minutes and microwave power 300W for choline chloride:ethylene glycol.

Nowadays, with growing demand...

U cilju utvrđivanja reakcije novih hibrida uljane repice na povećanu količinu dušika u prihrani izračunatu na temelju analize tla provedena su dvogodišnja istraživanja na antropogeniziranom, eutrično smeđem tlu u Zagrebu. U pokuse je bilo uključeno sedam hibrida uljane repice i tri varijante prihrane dušikom koje uključuju zalihu mineralnog dušika u tlu. U 2013. godini najveći prinos sjemena i ulja ostvarili su hibridi PR44W29 i PR46W20, a u 2014. godini Hybrirock i PR44W29. S povećanjem količine dušika u prihrani (73 + 50 kg ha-1 N), odnosno do ukupno 200 kg ha-1 raspoloživog dušika u tlu signifikantno se povećao prinos sjemena samo u 2013. godini.

Monovarietal virgin olive oils have a special importance in the olive bio-diversity preservation. Ripening index is used mainly as a guideline to establish the optimum olive harvest time in order to produce high quality virgin olive oils with well-balanced oil yield and content of bioactive compounds. Influence of cultivar, year and growing location on fruit quality parameters during fruit ripening was studied. The present data provide information about the maturation patterns of the most important Croatian cultivar Oblica and Italian cultivar Leccino harvested at bi-weekly periods during three crop seasons. Ripening index, fruit dry matter content and oil content expressed on a dry matter (%) and the mass of fresh olives were analyzed. The fruits were processed by same way, using centrifugal extraction on Abencor laboratory oil mill, after which the extractability was calculated. Mutual correlation of examined parameters and correlated relations of these parameters with the climatic conditions during three consecutive years of research was done. The olive fruit parameters significantly depend on the cultivar, year, climate and the fruit ripening index. The dry matter content in Oblica cultivar ranged from 32.0 to 45.6% and the average value was 38.67%, while the dry matter in Leccino ranged from 38.7 to 52.9% with average value of 43.93%. Oil content, when expressed on a dry weight basis, increased in both cultivars with the ripening. The average value of the oil content in Oblica was 41.5% and in Leccino 36.4%. There was a significant positive correlation between the ripening index and the dry matter content and oil content. The dry matter content was positively correlated with the amount of rainfall in the early stages of fruit development. Differences in extractability depending on the harvest time and cultivar were recorded.

Specifični sastav masnih kiselina lanenog ulja (preko 50 % α-linolenske masne kiseline i preko 90 % nezasićenih masnih kiselina) predstavlja značajni problem pri čuvanju i određivanju trajnosti ovog proizvoda. Cilj ovog istraživanja bio je utvrditi utjecaj tri različita načina proizvodnje lanenog ulja (hladno prešanje, prešanje nakon kondicioniranja i ultrazvučna ekstrakcija) iz četiri sorte lana na iskorištenje te trajnost proizvedenog ulja kroz šest mjeseci skladištenja. Kako bi se utvrdio stupanj oksidacije ulja određeni su primarni i sekundarni produkti oksidacije. U uljima je određen i ciklolinopeptid-E (specifična hidrofobna skupina peptida koji zaostaju u hladno prešanom lanenom ulju) primjenom HPLC. Iako su najveća iskorištenja dobivena prešanjem nakon kondicioniranja sjemena (84, 5-88, 7 %), hladno prešana ulja su pokazala najbolju održivost. Ultrazvučna ekstrakcija imala je znatno slabije iskorištenje (54, 1-65, 0 %). U svim uzorcima ulja detektiran je oksidirani ciklolinopeptid-E čija koncentracija proporcionalno raste s vremenom skladištenja. Vrijednosti peroksidnog broja svih skladištenih uzoraka su u skladu s Pravilnikom o jestivim uljima i mastima (2012.), ali nedovoljan pokazatelj oksidacijskog kvarenja lanenog ulja zbog porasta ciklolinopeptida-E.

The final stage of edible soybean oil manufacture is refining, the most delicate phase of which is bleaching. At this step, undesirable substances are removed, such as pigments, traces of metals, phospholipids and certain degradation products. However, certain valuable compounds such as tocopherols and sterols may also be removed, significant loss of oxidative stability can occur, and fatty acid content may increase. To avoid these negative oil changes, bleaching parameters such as the concentration of bleaching clay, temperature and duration should be optimized. Since bleaching conditions depend on the properties of the bleaching clay as well as on the type of crude oil, bleaching parameters should be optimized with different types of clay for each vegetable oil. Since such optimization has not yet been reported for soybean oil treated with Pure-Flo® Supreme Pro-Active bleaching adsorbent, this study investigates the effect of bleaching parameters on bleaching efficiency, oxidative stability and the content and composition of bioactive compounds (tocopherols and sterols) using the above mentioned clay in this type of oil. Results show that the amount of clay had the greatest influence on bleaching efficiency, especially according to the Lovibond scale, on transparency, and on phosphorus content. Temperature and clay amount significantly affected oxidative stability, in particular the formation of secondary oxidation products. Increasing the amount of clay decreased tocopherol content of the bleached oil. Neutralized soybean oil bleached for 20 min at 95 °C with 1 % Pure-Flo® Supreme Pro-Active bleaching clay showed the highest oxidative stability, best bleaching efficiency, and most favourable sterol content, although tocopherol content was reduced.

Cilj ovog rada bio je odrediti utjecaj parametara proizvodnje ulja na sastav masnih kiselina, udjel i sastav nekih bioaktivnih komponenata kao i na oksidacijsku stabilnost nerafiniranih ulja konoplje. U radu su provedena ispitivanja na uzorcima ulja konoplje proizvedenih laboratorijskim postupkom na dva različita načina. U proizvedenim uzorcima ulja određen je peroksidni broj, udio tokoferola i pigmenata te sastav masnih kiselina. Analize su pokazale da primijenjeni postupci proizvodnje ne narušavaju oksidacijsku stabilnost proizvedenih uzoraka ulja, a nerafinirana ulja imaju veći udjel visokovrijednih bioaktivnih komponenti u odnosu na hladno prešana ulja.

Research from the past decade suggest that virgin rapeseed oils have higher nutritional value than the ones produced by cold pressing. Heating of the seeds prior the oil extraction increases the amount of bioactive compounds such as tocopherols, sterols and polyphenols. Furthermore, applying heat during conditioning of the rapeseed can have effect on the sensory characteristics of the produced oil. The aim of our study was to determine changes in volatile components caused by increase of the conditioning temperature during the production of virgin rapeseed oil. For this experiment oils were produced by using the expeller press after condition the seeds at 60, 80 and 100 °C for 30 minutes. Cold pressed oil was produced by pressing the unconditioned seeds. Isothiocyanates were the dominant volatiles of cold pressed rapeseed oil making more than 55% of total volatile components. Conditioning the seed at 60 °C increased isothiocyanates concentration due to enhanced myrosinase activity. Using higher temperatures (80 and 100 °C) caused myrosinase inactivation, consequently decreasing isothiocyanates concentration in these oils. Although isothiocianates were still dominant components of the oil produced after conditioning at 80 °C, their concentration were about 7, 5 times lower than in the oil produced at 60 °C. Increasing the conditioning temperatures to 80 and 100 °C caused higher concentrations of nitriles and epithionitriles because of the thermal decomposition of glucosinolates. So the dominant components of virgin rapeseed oil produced after conditioning at 100 °C were nitriles making 53% of total volatiles. As expected, concentrations of aldehydes and ketones increased with temperature and pyrazines and furan derivates were only present in oil produced at 100 °C. All oils produced for this experiment differed significantly in volatile profile, indicating that optimizing the conditioning process can enable production of virgin rapeseed oil of a different and very specific sensory characteristics.

Cilj ovog rada bio je utvrditi utjecaj novih kultivara soje na sastav sojinog ulja ; sastav masnih kiselina, sterola i tokoferola. Ulje je proizvedeno ekstrakcijom po Soxhletu. Kultivar je imao značajan utjecaj na udjel pojedinačnih i ukupnih sterola, pojedinačnih i ukupnih tokoferola, na udjel palmitinske, stearinske, oleinske, linolne, α-linolenske, arahinske i behenske masne kiseline, na omjere polinezasićenih masnih kiselina (PUFA) i ukupnih tokoferola, kao i na omjere PUFA i svakog pojedinačnog tokoferola. Ulja kultivara koji su prisutni na tržištu i ulja novih kultivara proizvedenih oplemenjivanjem razlikuju se u prosječnom sastavu masnih kiselina, sterola i tokoferola.

Extra virgin olive oil is produced by mechanical and physical processes and therefore it keeps all valuable bioactive and aroma compounds. Fresh produced olive oil is always turbid and it has influence on the consumer’s choice. Filtration has recently imposes as last step in product finalization. During filtration, quantitative and qualitative changes take place, especially on minor components. The influence of filtration on phenolic content, α-tocopherol, oxidative stability and sensory attributes (oil aroma) of Oblica and Leccino olive oils were studied. Filtered oils of both investigated oils show a significant decrease on the total phenol content. In Oblica oil filtration had no effect on α-tocopherol content while in Leccino higher content of α-tocopherol was detected in unfiltered oil. After the filtration in both studied oils, oxidative stability loss was recorded of more than 14%. The filtration effect on oil aroma was evaluated by a panel tasters and sensory evaluation showed no significant influence on the sensory scores.

The aim of this work was to compare the composition of fatty acids and bioactive components of five unrefined oil (cold pressed olive, rapeseed, linseed, sunflower and hazelnut) in order to provide additional information about nutritive value of these oils. The composition of fatty acids determines the properties of oil while bioactive components (chlorophylls, tocopherols, and phenols) act as antioxidants in oils but they also have biological effect. All samples of oil fulfil the basic quality parameters according to national regulations. The fatty acid composition in the analysed samples of olive, rapeseed and sunflower oil is in accordance with national regulations, while the fatty acid composition of linseed oil and hazelnut oil is in accordance with the literature. Flaxseed oil is rich in essential omega-3 fatty acids. In olive oil is established the highest amount of chlorophyll, followed by rapeseed oil. Hazelnut oil and sunflower oil are characterized with a high concentration of tocopherols and low concentration of phenols. Olive oil contains the highest amount of phenolic compounds, and it is the only oil that contains flavonoids and oleuropein. Rapeseed oil contains a high proportion of phenolic compounds with canolol as predominant phenolic compound. Antioxidant activity was determined by DPPH method and found that sunflower oil has the best ability to bleach DPPH radicals

Flaxseed oil got its popularity mostly because of essential α-linoleic acid (omega-3) fatty acid. Such high yield of omega-3 (more than 50%) makes this oil very susceptible to oxidation. From numerous previous studies it is known that main antioxidants in vegetable oils are group of eight tocols ; four tocopherols and four tocotrienols. Recently a new compound that belongs to this group has gain interest in scientific community. Plastochromanol-8 is natural occurring homolog of γ-tocotrienol which can be found mostly in flaxseed oil and, in smaller quantity, in rapeseed oil. It was described as a powerful antioxidant which is connected with oils rich in α-linoleic acid and a second most represented in flaxseed oil after γ-tocopherol. Aim of this research was to determine influence of cold pressing (CP) and pressing of oil after 30 minute conditioning on 60° C (P60) of seed from four different cultivars on tocopherol and plastochromanol-8 content and to determine their antioxidant capacity. Oil was produced from three brown seed varieties and one yellow. Research was done trough three consecutive years. Plastochromanol-8 was detected in all produced oils in the range between 27-43 % of total tocopherols with γ-tocopherol making the most between 55-72 %. Their presence was significantly different between cultivars but influence of production process was not found. Total tocopherols and γ-tocopherol correlated significantly with DPPH radical scavenging activity. Contrary to other published researches on plastochromanol-8 its presence did not show significant correlation with antioxidant activity.

Conditioning of the seed prior the oil extraction is conducted to improve oil yield but it can also significantly increase amount of bioactive compounds. Despite these findings, consumers still prefer cold pressed oils over nonrefined ones. The aim of this study was to determine how different temperatures of conditioning influence nutritional properties and quality of rapeseed oil. Oil was produced from rapeseed cultivar PR 46 W20 (Pioneer) by cold pressing (CP) and by pressing seeds conditioned at 60, 80 and 100ºC for 30 min (HP60, HP80, HP100). The quality parameters of all produced oils were within limits of national regulations. Production process significantly affected unsaturated fatty acids of nonrefined oils but changes did not correlate with temperature increase. Conditioning of the rapeseed increased nutritional value of the oils because it did not change composition and content of tocopherols and at the same time it increased levels of plastochromanol-8 and polyphenols. Amount of canolol, polyphenol that was in cold pressed oils detected only in traces, linearly increased with temperature used. Conditioning also significantly affected profile of volatile components. The dominant volatile components of cold pressed rapeseed oil were isothiocyanates and sulfur components, together making 70% of total volatile components. Conditioning at 60°C furthermore increased their content (80% of total) probably because of higher myrosinase activity. Conditioning at 80 and 100°C significantly decreased levels of isothiocyanates and sulfur components at the same time increasing amount of nitrile components that are formed during the heating process. In addition, conditioning at 100 °C caused the formation of pyrazines, components responsible for nutty and roasted flavor of the oil. Despite significant difference in volatile components profile, all produced oils were given high scores on sensory evaluation by panel, and no significant difference between the sensory scores was found.

Cilj ovog istraživanja bio je odrediti svojstva repičinoga ulja proizvedenoga iz kultivara koji se uzgajaju na području Republike Hrvatske, te odrediti utjecaj načina proizvodnje sirovoga ulja kao i procesa rafinacije na kvalitetu, sastav masnih kiselina, udio bioaktivnih komponenata te na oksidacijsku stabilnost repičinoga ulja. Rezultati su pokazali kako je udio dominantnih masnih kiselina, sastav i udio sterola, karotenoida i tokoferola odlika pojedinog kultivara, a klimatske prilike značajno utječu na varijaciju rezultata navedenih parametara. U početnoj fazi razvoja sjemena stresni uvjeti uzrokuju smanjenje udjela karotenoida i α- tokoferola, ali povećanu sintezu plastokromanola-8 i fenolnih spojeva. Način proizvodnje ulja značajno utječe na udio i sastav negliceridnih spojeva repičinoga ulja. Kondicioniranjem sjemena znatno se povećava udio sterola i pigmenata, γ- tokoferola i ukupnih tokoferola. Najzastupljeniji fenolni spoj je kanolol čiji se udio kondicioniranjem povećava do 56 puta. Ulja proizvedena ekstrakcijom organskim otapalom sadrže više sterola i α-tokoferola u odnosu na ulja proizvedena prešanjem. Rafinacijom repičinoga ulja smanjuje se udio sterola, tokoferola, a posebno fenola, dok kanolol u potpunosti nestaje. Međutim, tijekom rafinacije dolazi do sinteze fenilindana, specifičnog spoja rafiniranoga jestivoga repičinoga ulja koji se odlikuje snažnim antioksidacijskim djelovanjem.

In this work an HPLC method for determination of polycyclic aromatic hydrocarbons (PAH) in edible oils on a DACC (donor-acceptor complex chromatography) column coupled with an on-line HPLC system with fluorescent detection. Method was used to determine the content of individual PAHs in the refined sunflower oil, virgin olive oil, cold pressed pumpkin seed oil, dark sesame oil and pumpkin seed oil produced with roasting obtained from domestic market. Calibration and validation were conducted for 13 individual PAHs among which are all 8 PAHs that are listed as priorities for determination in food and environment by both European Commission and US Environmental Protection Agency (EPA). Correlation coefficients of calibration curves for all standards were above 0.999 in selected range and all validation parameters (limit of detection, limit of quantification, accuracy and precision) were within limits set by European regulation. Content of PAHs in cold pressed pumpkin seed oil, roasted pumpkin seed oil and especially dark sesame oil was several-fold higher than the recommendations set by different European oil research and production organizations even though for both pumpkin seed oils it was lower than limits set by official European legislation. High content of cancerogenous heavy fraction PAHs were found in dark sesame oil that advises to limitation of its consumption in human diet.

Refining is the last stage of edible rapeseed oil production and it determines the quality of the final product. It is designed to remove undesirable supstances, but can also cause significant loss of valuable compounds, especially polyphenols. The aim of this study was to investigate influence of each refining step on polyphenol composition of rapeseed oil. Crude rapeseed oil and industrially neutralized, bleached and deodorized rapeseed oil were obtained from Zvijezda d.d., Zagreb, Croatia. Polyphenolic composition of oil samples was determined using high performance liquid chromatography with mass spectrometry. Crude rapeseed oil contained the highest amount of total polyphenols. Total polyphenol content decreased with every step of the refining process, and in comparison with crude oil, total polyphenolic content of edible rapeseed oil was 10 times lower. The greatest loss of polyphenolic compounds was observed in the processes of deodorization (67%) followed by neutralization (63%) and bleaching (16%). The dominant polyphenolic compound of the crude rapeseed oil was canolol, derivate of sinapic acid, while phenylindane, dimere of canolol, was dominant polyphenolic compound of the edible rapeseed oil. The content of canolol in the process of neutralization declined 80%. Bleaching and deodorization further reduced the content of canolol whose content in the edible oil is negligible. Such great loss of canolol can partially be explained by processing conditions and partially by formation of phenylindane. Because of much lower loss of phenylindane in processes of bleaching and deodorization, one could conclude that phenylindane is more stable compound.