Characterization of the aroma properties in fragrant rapeseed oil and aroma variation during critical roasting phase

Rapeseed oil is one of the third most-produced vegetable oil in the world, which is appreciated for its characteristic flavor and high nutritional value. Fragrant rapeseed oil (FRO) produced by a typical roasting process is popular for its characteristic aroma, which has an annual consumption exceeding 1.5 million tons. However, the changes in aroma blueprint of FRO during the typical roasting processing are still unclear, which challenges rapeseed oil quality and consumer acceptance. Accordingly, the aim of this work was to investigate the aroma characteristics and their precursors pyrolysis behavior of FRO to provide a basis and guidance for the control of FRO aroma quality during production processing. First, a systematic review on summarizing, comparing, and critiquing the literature regarding the flavor of rapeseed oil, especially about employed analysis techniques (i.e., extraction, qualitative, quantitative, sensorial, and chemometric methods), identified representative/off-flavor compounds, and effects of different treatments during the processes (dehulling, roasting, microwave, flavoring with herbs, refining, oil heating, and storage) was performed. One hundred and thirty-seven odorants found in rapeseed oil from literature are listed, including aldehydes, ketones, acids, esters, alcohols, phenols, pyrazines, furans, pyrrolines, indoles, pyridines, thiazoles, thiophenes, further S-containing compounds, nitriles, and alkenes, and possible formation pathways of some key aroma-active compounds are also proposed. Nevertheless, some of these compounds require further validation (e.g., nitriles) due to lack of recombination experiments in the previous work. To wrap up, advanced flavor analysis techniques should be evolved toward time-saving, portability, real-time monitoring, and visualization, which aims to obtain a complete flavor profile of rapeseed oil. Aparting from that, studies to elucidate the influence of key roasting processing on the formation of aroma-active compounds are needed to deepen understanding of factors resulting in flavor variations of rapeseed oil. Following, a systematic comparison among five flavor trapping techniques including solid-phase microextraction (SPME), SPME-Arrow, headspace stir bar sorptive extraction (HSSE), direct thermal desorption (DTD), and solvent-assisted flavor evaporation (SAFE) for hot-pressed rapeseed oil was conducted. Besides, methodological validation of these five approaches for 31 aroma standards found in rapeseed oil was conducted to compare their stability, reliability, and robustness. For the qualification of the odorants in hot-pressed rapeseed oil, SAFE gave the best performance, mainly due to the high sample volumes, but it performed worse than other methods regarding linearity, recovery, and repeatability. SPME-Arrow gave good performances in not only odorant extraction but also quantification, which is considered most suitable for quantifying odorants in hot-pressed rapeseed oil. Taking cost/performance ratio into account, SPME is still an efficient flavor extraction method. Multi-method combination of flavor capturing techniques might also be an option of aroma analysis for oil matrix. Afterwards, by application of the Sensomics approach the key odorants in representative commercial FRO samples were decoded. On the basis of the aroma blueprint, changes of overall aroma profiles of oils and their key odorants were studied and compared in different roasting conditions. To better simulate industrial conditions, high temperatures (150-200 ºC) were used in our roasting study, which was rarely studied before. Identification and quantitation of the key odorants in FRO were well performed by means of the Sensomics concept. Glucosinolate degradation products were a special kind of key odorants existing in rapeseed oil. Most of the odorants showed first rising and then decline trends as the roasting process progressed. Aroma profile results showed that high-temperature-short time and low-temperature-long time conditions could have similar effects on the aroma profiles of roasted rapeseed oils, which could provide a reference for the time cost savings in industrial production. To gain the fundamental knowledge of the aroma formation in FRO, the thermal degradation behavior of progoitrin (the main glucosinolate of rapeseed) and the corresponding generated volatile products were investigated in liquid (phosphate buffer at a pH value of 5.0, 7.0, or 9.0) and solid phase systems (sea sand and rapeseed powder). The highest thermal degradation rate of progoitrin at high temperatures (150-200 ºC) was observed at a pH value of 9.0, followed by sea sand and then rapeseed powder. It could be inferred that bimolecular nucleophilic substitution reaction (SN2) was mainly taken place under basic conditions. The highest degradation rate under basic conditions might result from the high nucleophilicity of present hydroxide ions. Under the applied conditions in this study, 2,4-pentadienenitrile was the major nitrile formed from progoitrin during thermal degradation at high temperature compared to l-cyano-2-hydroxy-3-butene, which might be less stable. The possible formation pathways of major S-containing (thiophenes) and N-containing (nitriles) volatile (flavor) compounds were proposed. Hydrogen sulfide, as a degradation product of glucosinolates, could act as a sulfur source to react further with glucose to generate thiophenes. Overall, the present work comprehensively documented the effects of thermal conditions and matrices on the aroma characteristics, aroma profiles, and key odorants of hot-pressed rapeseed oil, which could provide data and theoretical basis for the flavor control of FRO under thermal treatment at actual production temperatures (150-200 °C).Rapsöl ist eines der am dritthäufigsten produzierten Pflanzenöle der Welt, welches für seinen charakteristischen Geschmack und hohen Nährwert geschätzt wird. Geröstetes Rapsöl (fragrant rapeseed oil, FRO), das durch ein typisches Röstverfahren hergestellt wird, ist wegen seines charakteristischen Aromas beliebt und jährlich werden mehr als 1,5 Millionen Tonnen produziert. Allerdings sind die Veränderungen im Aromaprofil von FRO während der typischen Röstverarbeitung noch unklar, was die Rapsölqualität und die Verbraucherakzeptanz herausfordert. Dementsprechend war das Ziel dieser Arbeit, die Aromaeigenschaften und das Pyrolyseverhalten der Vorläuferverbindungen von FRO zu untersuchen, um eine Grundlage und Anleitung für die Kontrolle der FRO-Aromaqualität während des Herstellungsprozesses zu liefern. Zuerst wurde eine systematische Übersicht aus der Literatur über die Zusammenfassung, den Vergleich und die Kritik zum Aroma von Rapsöl, insbesondere zu den verwendeten Analysetechniken (d. h. Extraktion, qualitative, quantitative, sensorische und chemometrische Methoden), identifizierte repräsentative Verbindungen und Fehlaromen, und Auswirkungen verschiedener Prozesse während der Herstellung (Schälen, Rösten, Mikrowellenbehandlung, Aromatisierung mit Kräutern, Raffination, Ölerhitzung und Lagerung) durchgeführt. Einhundertsiebenunddreißig in Rapsöl beschriebene Aromastoffe sind aufgelistet, darunter Aldehyde, Ketone, Säuren, Ester, Alkohole, Phenole, Pyrazine, Furane, Pyrroline, Indole, Pyridine, Thiazole, Thiophene, weitere S-haltige Verbindungen, Nitrile und Alkene. Die mögliche Bildungswege einiger wichtiger aromaaktiver Verbindungen werden ebenfalls vorgeschlagen. Dennoch erfordern einige dieser Verbindungen eine weitere Validierung (z. B. Nitrile) aufgrund fehlender Rekombinationsexperimente in den vorherigen Arbeiten. Abschließend sollten fortschrittliche Aromaanalysetechniken in Richtung Zeitersparnis, Übertragung, Echtzeitüberwachung und Visualisierung weiterentwickelt werden, um ein vollständiges Aromaprofil von Rapsöl zu erhalten. Abgesehen davon sind Studien zur Aufklärung des Einflusses wichtiger Röstverfahren auf die Bildung aromaaktiver Verbindungen erforderlich, um das Verständnis der Faktoren zu vertiefen, die zu Aromavariationen von Rapsöl führen. Im nächsten Schritt wurde in systematischer Vergleich zwischen fünf Techniken zur Extraktion von Aromastoffen, darunter Festphasen-Mikroextraktion (solidphase microextraction, SPME), SPME-Arrow, headspace sorptive extraction (HSSE), direkte thermische Desorption (DTD) und lösungsmittelunterstützte Aromaverdampfung (solvent assisted flavor evaporation, SAFE) für heißgepresstes Rapsöl durchgeführt. Außerdem wurde eine methodische Validierung dieser fünf Ansätze für einunddreißig in Rapsöl gefundene Aromastoffe durchgeführt, um ihre Stabilität, Zuverlässigkeit und Robustheit zu vergleichen. Bei der Qualifizierung der Aromasstoffe in heißgepresstem Rapsöl erzielte die SAFE, vor allem aufgrund der hohen Probenvolumina, die beste Performance, schnitt aber hinsichtlich Linearität, Wiederfindung und Reproduzierbarkeit schlechter ab als andere Methoden. SPME-Arrow zeigte gute Leistungen nicht nur bei der Extraktion von Aromastoffen, sondern auch bei der Quantifizierung. Sie wurde daher als am besten geeignet für die Quantifizierung von Aromastoffen in heißgepresstem Rapsöl angesehen. Unter Berücksichtigung des Preis-Leistungs-Verhältnisses ist die klassiche SPME aber immer noch eine effiziente Aromaextraktionsmethode. Eine Kombination aus mehreren Methoden zur Erfassung von Aromen könnte auch eine Option der Aromaanalyse für die Ölmatrix sein. Anschließend wurden durch Anwendung des Sensomics-Ansatzes die wichtigsten Aromastoffe in repräsentativen kommerziellen FRO-Proben entschlüsselt. Auf der Grundlage des Aroma-Blueprints wurden Änderungen im Gesamtaromaprofil der Öle und ihrer Schlüsselaromastoffe unter verschiedenen Röstbedingungen untersucht und verglichen. Um industrielle Bedingungen besser zu simulieren, wurden in unserer Röststudie hohe Temperaturen (150-200 ºC) verwendet, die zuvor selten untersucht wurden. Die Identifizierung und Quantifizierung der wichtigsten Aromastoffe in FRO wurde mithilfe des Sensomics-Konzepts gut durchgeführt. Glucosinolat-Abbauprodukte waren eine besondere Art von Hauptaromastoffen, die in Rapsöl vorhanden sind. Die meisten Aromastoffe zeigten mit fortschreitendem Röstvorgang zunächst steigende und dann fallende Tendenzen. Die Ergebnisse der Aromaprofile zeigten, dass Hochtemperatur-Kurzzeit- und Niedrigtemperatur-Langzeit-Bedingungen ähnliche Auswirkungen auf die Aromaprofile von gerösteten Rapsölen haben könnten, was eine Referenz für die Zeitkosteneinsparungen in der industriellen Produktion liefern könnte. Um grundlegende Erkenntnisse über die Aromabildung bei FRO zu gewinnen, wurde das thermische Abbauverhalten von Progoitrin (dem Hauptglucosinolat in Rapssamen) und den entsprechend entstehenden flüchtigen Produkten in Flüssigkeits- (Phosphatpuffer bei einem pH-Wert von 5,0, 7,0 oder 9,0) und Festphasensystemen (Seesand und Rapspulver) untersucht. Die höchste thermische Abbaurate von Progoitrin bei hohen Temperaturen (150-200 ºC) wurde bei einem pH-Wert von 9,0 beobachtet, gefolgt von Seesand und Rapspulver. Es konnte gefolgert werden, dass die bimolekulare nukleophile Substitutionsreaktion (SN2) hauptsächlich unter basischen Bedingungen stattfand. Die höchste Abbaurate unter basischen Bedingungen könnte aus der hohen Nukleophilie der vorhandenen Hydroxidionen resultieren. Unter den angewandten Bedingungen in dieser Studie war 2,4-Pentadiennitril das Hauptnitril, das während des thermischen Abbaus bei hoher Temperatur aus Progoitrin gebildet wurde, verglichen mit l-Cyano-2-hydroxy-3-buten, das weniger stabil sein könnte. Die möglichen Bildungswege der wichtigsten S-haltigen (Thiophene) und N-haltigen (Nitrile) flüchtigen (Aroma-)Verbindungen wurden vorgeschlagen. Schwefelwasserstoff als Abbauprodukt von Glucosinolaten könnte als Schwefelquelle dienen, die dann weiter mit Glucose zu reagieren, um Thiophene zu erzeugen. Insgesamt dokumentiert die vorliegende Arbeit umfassend die Auswirkungen thermischer Bedingungen und Matrizes auf die Aromaeigenschaften, Aromaprofile und Hauptaromastoffe von heißgepresstem Rapsöl, die Daten und theoretische Grundlagen für die Aromakontrolle von FRO unter thermischer Behandlung bei den in der Produktion tatsächlichen verwendeten Temperaturen (150-200 °C)

Nanotribology and Nanomechanics of Thin Films Including Material Characterization, Mechanical Wear, Adhesion and Lubrication

The present work is dedicated to addressing nanotribological issues of ultra-thin (sub-10 nm) films at contacting interfaces. In devices such as micro-electro-mechanical systems (MEMS), thin films are deposited for specific functions. In some occasions, mechanical durability of the thin films is also important. Magnetic storage hard disk drives (HDD) are a good example where nanotribology at the head-disk interface (HDI) is extremely important. Especially in recent years, where the areal density increases exponentially and the write/read head has been brought as close to as less than 10 nm to the disk surface. As a result, direct contact is possible to occur at such small distance and such unfavorable contact will cause mechanical wear and demagnetization. Nanometer thick diamond like carbon (DLC) and lubricant films provide important protection and study of their failure mechanisms is necessary. The present thesis has conducted research to understand the nanotribology of thin films in the multilayered system used in HDDs. The majority of the work is measurement of the nanomechanical and nanotribological properties of the solid thin films with thickness of less than 20 nm. A method combining finite element analysis (FEA) and nanoindentation was proposed to extract nanomechanical properties from nanoindentation data for multilayered samples. A highly sensitive nanomechanical transducer was introduced to perform sub-5 nm shallow nanoindentation experiments on thin films deposited at different conditions. To study the tribological performance of DLC films at high temperatures up to 300 °C, the present work performs nanoscratch and nanowear tests on a 3-nm thick DLC film. The results show the wear rate of DLC films begin to increase abruptly at around 200°C and this degradation of wear resistance is irreversible. The present thesis also proposes a mathematical model to quantitatively predict the hydrodynamic lubrication effects of the molecularly thin lubricant between the head and the disk surfaces. After considering the nanorheological behavior of the lubricant, the model is able to make predictions of contacting forces and pressures and explain the tribological role of the lubricant in terms of continuum mechanics. Lastly, present thesis proposed a model considering Van der Waals forces between lubricants on the disk and on the head. The proposed model provides stricter criterion for onset of adhesion induced lubricant-transfer between the two wet surfaces and is in better agreement with Molecular Dynamics simulations than conventional models. In summary, the findings above center about nanomechanics and nanotribology at the interfaces of the magnetic storage hard disk. However, these findings can also extend their applications to other MEMS devices where tribology issues are of important concerns. The shallow nanoindentaton instrument and FEA-based characterization method can be applicable any other solid thin films. The high-temperature tribological properties of a ultra-thin DLC films utilize a unique test rig but the findings are generally instructive in understanding behaviors of DLC at high temperature. The nano-lubrication model for a lubricated single asperity can be an addition of current contact mechanics which usually neglects the presence of lubricants

Nanotribology and Nanomechanics of Thin Films Including Material Characterization, Mechanical Wear, Adhesion and Lubrication

The present work is dedicated to addressing nanotribological issues of ultra-thin (sub-10 nm) films at contacting interfaces. In devices such as micro-electro-mechanical systems (MEMS), thin films are deposited for specific functions. In some occasions, mechanical durability of the thin films is also important. Magnetic storage hard disk drives (HDD) are a good example where nanotribology at the head-disk interface (HDI) is extremely important. Especially in recent years, where the areal density increases exponentially and the write/read head has been brought as close to as less than 10 nm to the disk surface. As a result, direct contact is possible to occur at such small distance and such unfavorable contact will cause mechanical wear and demagnetization. Nanometer thick diamond like carbon (DLC) and lubricant films provide important protection and study of their failure mechanisms is necessary. The present thesis has conducted research to understand the nanotribology of thin films in the multilayered system used in HDDs. The majority of the work is measurement of the nanomechanical and nanotribological properties of the solid thin films with thickness of less than 20 nm. A method combining finite element analysis (FEA) and nanoindentation was proposed to extract nanomechanical properties from nanoindentation data for multilayered samples. A highly sensitive nanomechanical transducer was introduced to perform sub-5 nm shallow nanoindentation experiments on thin films deposited at different conditions. To study the tribological performance of DLC films at high temperatures up to 300 °C, the present work performs nanoscratch and nanowear tests on a 3-nm thick DLC film. The results show the wear rate of DLC films begin to increase abruptly at around 200°C and this degradation of wear resistance is irreversible. The present thesis also proposes a mathematical model to quantitatively predict the hydrodynamic lubrication effects of the molecularly thin lubricant between the head and the disk surfaces. After considering the nanorheological behavior of the lubricant, the model is able to make predictions of contacting forces and pressures and explain the tribological role of the lubricant in terms of continuum mechanics. Lastly, present thesis proposed a model considering Van der Waals forces between lubricants on the disk and on the head. The proposed model provides stricter criterion for onset of adhesion induced lubricant-transfer between the two wet surfaces and is in better agreement with Molecular Dynamics simulations than conventional models. In summary, the findings above center about nanomechanics and nanotribology at the interfaces of the magnetic storage hard disk. However, these findings can also extend their applications to other MEMS devices where tribology issues are of important concerns. The shallow nanoindentaton instrument and FEA-based characterization method can be applicable any other solid thin films. The high-temperature tribological properties of a ultra-thin DLC films utilize a unique test rig but the findings are generally instructive in understanding behaviors of DLC at high temperature. The nano-lubrication model for a lubricated single asperity can be an addition of current contact mechanics which usually neglects the presence of lubricants

Flow Past a Sphere and a Prolate Spheroid at Low Reynolds Numbers

The present work carries out numerical simulations of viscous incompressible flow past a sphere or a spheroid at low Reynolds numbers. When the flow passes a sphere or a spheroid, the flow will have its motion changed because of the shear stress from the surface of the object. This change of motion also differs at different Reynolds numbers based on the geometry of the sphere or spheroid. Many fluids researchers have conducted experiments to investigate the variations of the flow past a sphere at low Reynolds numbers. But the research on flow past a spheroid mainly focuses on cases at high Reynolds numbers (Re>105). Up to date, numerical study on flow past a spheroid at low and intermediate Reynolds numbers (<1000) has not been done thoroughly. The first part of this work is to investigate variations of the flow past a sphere occurring with increasing Reynolds number up to 400. The code used in this thesis is OpenFOAM which is an open source package providing a solver based on the Finite Volume Method. To verify the accuracy of the simulations by the code, results for velocity, vorticity and drag coefficient at very low Reynolds number (Re<0.1) are compared with exact solutions by Stokes Law. Then variations of the flow pattern are displayed up to Reynolds number 400. Some characteristics such as the drag coefficient, wake length and wake angle are recorded for contrast with data in publications. The wake length and separation angle both show logarithmic relationship with the Reynolds number. Flow patterns such as streamline around the sphere and periodic shedding are also discussed on the ground of previous knowledge. The second part will investigate the flow past a prolate spheroid. Discussion on this topic is developed in the regime of low Reynolds number (Re<1000). The present work investigates cases at very low Reynolds numbers (Re<0.1) and compares the results with exact solutions predicted by previous researchers. For higher Reynolds numbers, present work mainly focuses on studying variations of the drag coefficient with the Reynolds number and aspect ratio. The simulation shows that a spheroid has larger drag coefficient than a sphere at lower Reynolds numbers and then tends to be the smaller one for higher Reynolds numbers

Case report:Multiple abscesses caused by Porphyromonas gingivalis diagnosed by metagenomic next-generation sequencing

BackgroundExtraoral infection by Porphyromonas gingivalis (P. gingivalis) is extremely rare and challenging to diagnose because the fastidious pathogen is difficult to culture by traditional methods. We report the first case of a patient with multiple abscesses in muscles and the brain with dura empyema due to P. gingivalis, which was diagnosed by metagenomic next-generation sequencing (mNGS).Case presentationA 65-year-old male patient was admitted to our hospital for multiple lumps in his body. Brain magnetic resonance imaging (MRI) and lower-limb computed tomography (CT) revealed multiple abscesses in the brain and muscles. A diagnosis of P. gingivalis infection was made based on mNGS tests of blood, cerebrospinal fluid (CSF), and pus samples, as the traditional bacterial culture of these samples showed negative results. Target antibiotic therapy with meropenem and metronidazole was administered, and CT-guided percutaneous catheter drainage of abscesses in both thighs was performed. The size of muscle abscesses reduced significantly and neurological function improved. The patient was followed up for 4 months. No abscesses re-appeared, and the remaining abscesses in his backside and both legs were completely absorbed. He can speak fluently and walk around freely without any neurological deficits.ConclusionMetagenomic next-generation sequencing is helpful for early diagnosis and subsequent treatment of P. gingivalis-associated multiple abscesses

Pressure-Arching Characteristics of Fractured Strata Structure during Shallow Horizontal Coal Mining

It is an important problem for the alternated strong and weak roof weighting to threat the safety of working face during shallow coal mining and the total thickness breaking of the thin bedrock to cause the serious ground subsidence. To reveal the mechanism of the abnormal mining damage, the pressure-arching rule in overlying strata was studied. Based on the monitoring data of the typical shallow coal working face, the mechanical models of the symmetrical stress arch, the squeezed arch and the hinged structure of the fractured strata were established, and the difference of the load bearing capacity between the structures and the influencing factors was analysed by the deduced formula calculation. Then the evolution characteristics of the pressure-arch in the fractured strata were revealed by the numerical simulation analysis. The results show that the global pressure-arch of multilayer strata always exits in the surrounding rock and moves forward with continuous mining. The single pressure-arch and hinged structure are formed in each stratum under the global pressure-arch. The pressure-arch enables the fractured strata to carry load efficiently, and the instability of the pressure-arch can cause strong roof weighting and ground subsidence. These conclusions provide a theoretical reference for the stability control of the overlying strata structure under shallow coal mining

Indian monsoon variability on millennial-orbital timescales

The Indian summer monsoon (ISM) monsoon is critical to billions of people living in the region. Yet, significant debates remain on primary ISM drivers on millennial-orbital timescales. Here, we use speleothem oxygen isotope (δ18O) data from Bittoo cave, Northern India to reconstruct ISM variability over the past 280,000 years. We find strong coherence between North Indian and Chinese speleothem δ18O records from the East Asian monsoon domain, suggesting that both Asian monsoon subsystems exhibit a coupled response to changes in Northern Hemisphere summer insolation (NHSI) without significant temporal lags, supporting the view that the tropical-subtropical monsoon variability is driven directly by precession-induced changes in NHSI. Comparisons of the North Indian record with both Antarctic ice core and sea-surface temperature records from the southern Indian Ocean over the last glacial period do not suggest a dominant role of Southern Hemisphere climate processes in regulating the ISM variability on millennial-orbital timescales

East Asian hydroclimate modulated by the position of the westerlies during Termination I.

Speleothem oxygen isotope records have revolutionized our understanding of the paleo East Asian monsoon, yet there is fundamental disagreement on what they represent in terms of the hydroclimate changes. We report a multiproxy speleothem record of monsoon evolution during the last deglaciation from the middle Yangtze region, which indicates a wetter central eastern China during North Atlantic cooling episodes, despite the oxygen isotopic record suggesting a weaker monsoon. We show that this apparent contradiction can be resolved if the changes are interpreted as a lengthening of the Meiyu rains and shortened post-Meiyu stage, in accordance with a recent hypothesis. Model simulations support this interpretation and further reveal the role of the westerlies in communicating the North Atlantic influence to the East Asian climate

Medicarpin induces G1 arrest and mitochondria-mediated intrinsic apoptotic pathway in bladder cancer cells

Bladder cancer (BC) is the tenth most commonly diagnosed cancer. High recurrence, chemoresistance, and low response rate hinder the effective treatment of BC. Hence, a novel therapeutic strategy in the clinical management of BC is urgently needed. Medicarpin (MED), an isoflavone from Dalbergia odorifera, can promote bone mass gain and kill tumor cells, but its anti-BC effect remains obscure. This study revealed that MED effectively inhibited the proliferation and arrested the cell cycle at the G1 phase of BC cell lines T24 and EJ-1 in vitro. In addition, MED could significantly suppress the tumor growth of BC cells in vivo. Mechanically, MED induced cell apoptosis by upregulating pro-apoptotic proteins BAK1, Bcl2-L-11, and caspase-3. Our data suggest that MED suppresses BC cell growth in vitro and in vivo via regulating mitochondria-mediated intrinsic apoptotic pathways, which can serve as a promising candidate for BC therapy