Search Results (20)

The relationship between the structure characteristics and performances of coal-based hydrogenation isomeric (CTL) base oil and metallocene-catalyzed coal-based poly-alpha-olefin (mPAO) base oil is clarified in this paper. CTL and mPAO were compared with typical petroleum-based and natural gas-based commercial API III and IV base oils. Pressurized differential scanning calorimetry (PDSC), the rotary bomb oxidation test (RBOT), and a four-ball friction tester were used to evaluate the oxidation stability and lubrication performance of base oils under different working conditions. The sensitivity of different base oils to typical antioxidants and extreme-pressure antiwear agents was compared. In particular, the composition and structure of CTL base oil are clearly different from GTL and mineral base oil. The coal-based CTL and mPAO base oils exhibit commendable viscosity–temperature properties, coupled with low-temperature fluidity, fire safety, and minimal evaporation loss. The lubricating properties, oxidation stability, and sensitivity to extreme-pressure antiwear agents of CTL are close to those of similar base oils. However, the sensitivity of CTL to typical antioxidants is relatively poor. In addition, compared with commercial PAO base oil, mPAO has a lower isomerization degree and fewer isomerization types. The oxidation stability and sensitivity to typical antioxidants of mPAO base oil are comparable with those of commercial PAO base oil, while its lubrication performance and sensitivity to typical extreme-pressure antiwear agents are significantly better than those of commercial PAO base oil. Full article

In situ combustion (ISC), an efficient and economical method for enhancing heavy oil recovery in high-pressure, high-viscosity, and thermally challenged reservoirs, relies on the kinetics of crude oil oxidation. Despite an increased focus on kinetic models, there is a gap in understanding how oxidation kinetic parameters impact ISC effectiveness in heavy oil reservoirs. This study addresses this by selecting heavy oil samples from the G Block in the Liaohe oilfield and the M Block in the Huabei oilfield and conducting ramped temperature oxidation (RTO), pressure differential scanning calorimetry (PDSC), and thermogravimetric analysis (TGA) experiments. RTO detailed the thermal conversion process, categorizing oxidation into low-temperature oxidation (LTO), fuel deposition (FD), and high-temperature oxidation (HTO) stages. PDSC and TGA provided thermal characteristics and kinetic parameters. The feasibility of fire flooding was evaluated. Using CMG-STARS, an ISC model was established to analyze the impact of kinetic parameter changes. Activation energy significantly affected coke combustion, while the pre-exponential factor had a notable impact on cracking reactions. The recommended values for activation energy and the pre-exponential factor are provided. This study not only guides fire flooding experiments but also supports field engineering practices, particularly for in situ combustion in heavy oil reservoirs. Full article

Berry fruit seeds should be treated as a valuable waste product of the fruit industry. In the following study, oils from cranberry, black currant, red currant, strawberry and chokeberry seeds were extracted by conventional and pressurized liquid extraction. The quality of oils was assessed by determining oxidative stability (onset and maximum time of induction) with the use of pressure differential scanning calorimetry, fatty acids composition by gas chromatography and health indices, such as atherogenicity, thrombogenicity and hypocholesterolemic indexes. Additionally, health-promoting index was calculated. It was found that the fatty acid profile was not affected when pressurized liquid extraction was used. The major fatty acids in the studied oils were linoleic acid ranging from 36% for cranberry seed oil to 69% for chokeberry seed oil, followed by α-linolenoic acid in the case of cranberry, strawberry and red currant seed oils or by oleic acid for chokeberry and black currant seed oils. The oxidative stability of fats extracted with the use of pressurized solvent was significantly lower compared to oils obtained using the conventional extraction process, e.g., the maximum induction time for conventionally extracted chokeberry seed oil was 40.74 ± 0.66 min and 9.24 ± 0.57 min when pressurized liquid extraction was applied. The studied oils had low values of atherogenicity and thrombogenicity indexes, which, when combined with high values of hypocholesterolemic index, qualifies them as high nutritional quality oils. However, further studies regarding the process optimization are needed in order to obtain oils with improved quality, especially better oxidative stability. Full article

Barely explored in the prior literature, ruby chocolate was investigated in this study to explore its thermal properties. The fatty acid composition of ruby chocolate (RC) fat was determined using gas chromatography. Differential scanning calorimetry (DSC) was successfully used to determine the melting behavior and polymorphic forms of the cocoa fat and milk fat present in the RC. The oxidative stability of the fat extracted from the RC was studied with the use of pressurized differential scanning calorimetry (PDSC). The thermal behavior of the chocolate and the fat were investigated using thermogravimetry (TGA). The thermal profile and characteristics of the RC showed how the parameters compared with those of dark and milk chocolate. The melting temperature of the RC obtained by DSC was more similar to that of milk chocolate than to that of dark chocolate. Regression analysis of the PDSC data for the fat extracted from the RC was characterized by very high correlation coefficients (>0.99). It was noticed there was no statistically significant difference between the values of the activation energy (E_a) of the oxidation process for the fat extracted from the RC, obtained by the means of maximum temperature (dynamic mode) and maximum induction time (isothermal mode). Full article

Food byproduct streams can potentially be transformed into value-added products such as microbial lipids in bioprocesses based on the non-conventional Yarrowia yeast. The effect of culture conditions of Y. lipolytica KKP 379 wild strain in waste media on the efficiency of lipid accumulation, fatty acid composition, presence of selected sterols, yield and elemental composition of biomass has been studied. Batch and fed-batch bioreactor cultures were carried out in media with molasses hydrolysate (MH) and post-frying rapeseed oil. It was determined that biomass grown in MH contained more minerals than in medium with rapeseed post-frying oil. Considering the PDSC study, the T_max of oxidation induction ranged from 10.04–26.36 min for the analyzed samples. The biomass from fed-batch cultures with MH had the highest total sterol content (68.40 mg/g_oil), dominated by ergosterol at 60.16 mg/g. Feeding with post-frying rapeseed oil with new doses of mineral medium promoted maintaining the cellular lipid content at a high level (30.75–31.73%) for 50 h, with maximum yield at 37.50%. The results of the experiment showed that the cellular lipid accumulation efficiency of Y. lipolytica yeast and the content of sterols in the cell membrane can be manipulated by selecting waste substrates and culture mode. Full article

Placenta-derived stem cells (PDSCs), due to unique traits such as mesenchymal and embryonic characteristics and the absence of ethical constraints, are in a clinically and therapeutically advantageous position. To aid in stemness maintenance, counter pathophysiological stresses, and withstand post-differentiation challenges, stem cells require elevated protein synthesis and consequently augmented proteostasis. Stem cells exhibit source-specific proteostasis traits, making it imperative to study them individually from different sources. These studies have implications for understanding stem cell biology and exploitation in the augmentation of therapeutic applications. Here, we aim to identify the primary determinants of proteotoxic stress response in PDSCs. We generated heat-induced dose-responsive proteotoxic stress models of three stem cell types: placental origin cells, the placenta-derived mesenchymal stem cells (pMSCs), maternal origin cells, the decidua parietalis mesenchymal stem cells (DPMSCs), and the maternal–fetal interface cells, decidua basalis mesenchymal stem cells (DBMSCs), and measured stress induction through biochemical and cell proliferation assays. RT-PCR array analysis of 84 genes involved in protein folding and protein quality control led to the identification of Hsp70 members HSPA1A and HSPA1B as the prominent ones among 17 significantly expressed genes and with further analysis at the protein level through Western blotting. A kinetic analysis of HSPA1A and HSPA1B gene and protein expression allowed a time series evaluation of stress response. As identified by protein expression, an active stress response is in play even at 24 h. More prominent differences in expression between the two homologs are detected at the translational level, alluding to a potential higher requirement for HSPA1B during proteotoxic stress response in PDSCs. Full article

Conventional predictive control for permanent magnet synchronous motors (PMSMs) contains dual speed and current loops, and has a complex structure and multiple parameters to be tuned. Conventional predictive direct speed control (PDSC) exhibits an unsatisfactory steady-state performance. To tackle these issues, this paper presents a cascade-free modulated PDSC (MPDSC) scheme for PMSM drives. First, a speed predictive model is built, where a second-order sliding mode observer is employed to quickly and robustly estimate the load torque. Then, a dual objective cost function with speed and stator current tracking is designed, which improves the system’s steady-state performance. Furthermore, the analytical solution of the constrained optimal voltage vector is derived and it is synthesized by space vector modulation, resulting in a fixed switching frequency. Experimental results show that the proposed MPDSC has stronger robustness, and lower torque ripples and stator current harmonics compared to conventional PDSC. Full article

Natural antioxidants are known for their ability to scavenge free radicals and protect oils from oxidation. Our aim was to study the structural properties such as the number of hydroxyl groups and Bors criteria of phenolic substances leading to high antioxidant activity in oil in order to analyze common trends and differences in widespread in vitro antioxidant assays. Therefore, 20 different phenolic substances were incorporated into rapeseed oil and were measured using pressurized differential scanning calorimetry (P-DSC) and the Rancimat method. The Bors criteria had the highest influence on the antioxidant effect in rapeseed oil, which is why myricetin (MYR), fulfilling all Bors criteria, reached the highest result of the flavonoids. In the Rancimat test and P-DSC, MYR obtained an increase in oxidation induction time (OIT) of 231.1 ± 44.6% and 96.8 ± 1.8%, respectively. Due to differences in the measurement parameters, the results of the Rancimat test and P-DSC were only partially in agreement. Furthermore, we compared the results to in vitro assays (ABTS, DPPH, FC and ORAC) in order to evaluate their applicability as alternative rapid methods. These analysis showed the highest correlation of the oil methods with the results of the DPPH assay, which is, therefore, most suitable to predict the antioxidant behavior of oil. Full article

This work reports the effect of simple feeding strategies and temperature to obtain high-cell-density cultures of Rhodotorula glutinis var. rubescens LOCKR13 maximizing the de novo lipid productivity using deproteinated potato wastewater (DPW) as a basic medium. Feeding DPW with glucose enables a high yield of Rhodotorula glutinis var. rubescens LOCKR13 biomass (52 g _d.w. L⁻¹) to be obtained. The highest values of lipid accumulation (34.15%, w/w), production (14.68 g L⁻¹) and yield coefficients (Y_L/S: 0.242 g g⁻¹), and volumetric productivity (P_L: 0.1 g L⁻¹ h⁻¹) were reached by the strain in the two-stage fed-batch process at 20 °C. The lipid of yeast biomass was rich in oleic acid (^Δ9C18:1) and palmitic acid (C16:0), and the lower temperature of incubation significantly increased the MUFA (especially oleic acid) content. For the first time, a unique set of thermal analyses of the microbial oil was performed. The isotherms of the oxidation kinetics (PDSC) showed that lipids extracted from the biomass of red yeast had high oxidative stability. This feature of the yeast oil can be useful for long-shelf-life food products and can be promising for the production of biodiesel. Full article

Amaranth and quinoa are classed as pseudocereals that do not belong to the grass family, meaning they are not technically a grain. Both of them are seeds with tremendous nutritional value; compared to other cereals, they contain much more fat. The aim of the study was to present the parameters characterizing thermal properties of amaranth and quinoa oils, such as: oxidation induction time, oxidation kinetic parameters, and melting profile. In isolated oils, the peroxide value, oxidative stability by the Rancimat test (in 120 °C) and the pressure differential scanning calorimetry (PDSC) method (at 100, 110, 120, 130, 140 °C), fatty acids composition, and their distribution between the triacylglycerol positions were determined. The kinetic parameters of the oxidation process (activation energy, pre-exponential factor, and reaction rate constants) were calculated using the Ozawa–Flynn–Wall method and the Arrhenius equation. To measure the melting profile, the differential scanning calorimetry (DSC) method was used. Both types of seeds are a good source of unsaturated fatty acids. Induction time of oxidation suggests that amaranth oil may have better resistance to oxidation than quinoa oil. The melting characteristics of the oils show the presence of low-melting triacylglycerol fractions, mainly containing unsaturated fatty acids, which means that a small amount of energy is required to melt the fats. Full article

The purpose of the present study was to characterize lipid fraction extracted from five self-prepared and seven commercial cat foods using gas chromatography (GC) and pressurized differential scanning calorimetry (PDSC) techniques. Self-prepared food recipes were composed using BARFny kalkulator, software dedicated for balancing cat diets, and prepared on the basis of fresh raw meat and offal. Extracted fat fractions were compared qualitatively and quantitatively with literature data for the fat of whole prey items to check the main assumptions of the software used. The fatty acid (FA) composition and distribution were determined using GC. The PDSC method was used for the determination of the oxidative stability of extracted fats. The obtained results indicate that self-prepared cat foods contained a high level of essential fatty acids (EFA) but low oxidative stability, especially for those with significant amounts of polyunsaturated FA. The FA profile and oxidative stability were examined for four dry and three wet commercial cat foods. It was found that their omega-6 to omega-3 ratio was beneficial reaching 5.3:1 to 10.1:1, despite the low amount of EFA. The longer induction time was determined for fats extracted from commercial cat foods than for self-prepared ones, which indicate their higher oxidative stability. Full article

The aim of this work was to study the quality (oxidative stability), fatty acids (FAs) profile and their distribution in triacylglycerol (TAG) molecules of hunted game wild fat (HGWF) obtained from wild boar, badger, and wild goose. Health lipid indices were calculated. The determination of FAs composition was carried out by gas chromatographic analysis of fatty acid methyl esters (FAME). Enzymatic hydrolysis and thin layer chromatography were used to determine the positional distribution of FAs in the internal and external positions of triacylglycerols (the regiospecific structure of triacylglycerols) of the obtained HGWF. A pressure differential scanning calorimeter (PDSC) was used to determine the oxidative stability of tested HGWF. The lipid fraction isolated from subcutaneous adipose tissues was dominated by MUFA, on average 46–50% of total FAs, and by SFA, on average 32–36% of total FAs. Palmitic acid was located mainly in the internal position of TAGs of the analyzed HGWF, whereas external positions were occupied by unsaturated oleic acid. Such a structure is responsible for normal fat absorption from food and it prevents the formation of insoluble calcium salts. Considering FAs profile, quality and the oxidation stability among all tested fat samples, the boar fat seems to be the most favorable. Full article

The seeds of berry fruits are a component of fruit waste occurring in the production process. Circular economy rules focus on decreasing the amount of waste produced and reusing by-products when it is possible. To determine the possible applications of the studied fruit industry wastes, the thermal properties of berry seeds and of oil extracted from the tested material were examined. Differential scanning calorimetry (DSC), modulated differential scanning calorimetry (MDSC), and thermogravimetry (TG) of blackberry, chokeberry, and raspberry seeds were carried out. The properties of oil extracted in the Soxhlet apparatus were studied by pressure differential scanning calorimetry (PDSC), TG, and gas chromatography (GC) measurements. The results show that berry seeds lipids are from different melting fraction groups with a dominance of low-melting fraction, which consists of mono- and polyunsaturated fatty acids. There are also occurring residues of carbohydrates and inorganic, thermostable substances in the studied seeds. A GC analysis of oil confirms that the polyunsaturated fatty acids (PUFA) are most abundant and amount to 78.72 ± 0.06% in blackberry seed oil, 73.79 ± 0.14% in chokeberry seed oil, and 82.74 ± 0.03% in raspberry seed oil. The PDSC study showed that the most oxidative stable oil is blackberry seed oil, followed by raspberry and chokeberry seed oils. According to the obtained results, berry seeds can be used as a source of oil in food or other production chains. However, more detailed characteristics of berry seed oils are needed to determine their applicability. Full article

Diesel fuel mixtures with high concentrations of biodiesel have been investigated to analyze the technical feasibility of their use in diesel cycle engines regarding thermal and oxidative properties. The results of combined techniques of oxidative stability, high Pressurized Differential Scanning Calorimetry (P-DSC), Calculated Cetane Index (CCI), and calorific power were used to verify the effect of the thermal-oxidative stability as a function of the percentage of biodiesel in the mixtures. The obtained results evidenced that the thermal and oxidative stability decreased with the addition of biodiesel from 50 to 5% v/v. Low stability fuels require rapid use as the oxidation compounds degrade the product and impair vehicle performance, as well as lead to corrosion and clogging problems in various mechanical systems. Full article

Recently, consumers’ awareness is becoming a crucial aspect driving the food industry to develop new products with high nutritional value. The oil industry explores the use of less well-known plant materials such as avocado fruit which is a rich source of bioactive compounds. The objective of this study was to assess the quality and oxidative stability of avocado pulp oils during a 2-month storage period. Two avocado varieties, Hass and Reed, were selected and oil extraction was performed with the use of hexane. The extent of oxidative deterioration and oil stability were tested by measuring the acid value and peroxide value. The PDSC method was applied to evaluate the oxidative induction time. The composition of fatty acids and their distribution in internal (sn-2) and external (sn-1 and sn-3) positions in triacylglycerols were also analyzed. The acid value and the peroxide value of fresh extracted avocado oils reached approximately 0.6 mg KOH g⁻¹ fat and 5 meq O2 kg⁻¹ fat, respectively. Generally, during avocado oil storage both the acid values and the peroxide values were in accordance with Codex Alimentarius requirements (the limit for acid value is 4 mg KOH g⁻¹, while for peroxide value it is 15 meq O2 kg⁻¹). The Hass avocado pulp oil was characterized by a higher value of the oxidative induction time, about 111 min, compared to the oil extracted from Reed avocado pulp (61 min). The GC analysis revealed that avocado pulp oil could be considered a source of monounsaturated fatty acids. The dominant fatty acid found in this group was oleic acid with a percentage share of above 60%. In accordance with the results of fatty acids distribution in triacylglycerol molecules, the main fatty acids in the sn-2 position were linoleic acid and oleic acid and their percentage share in this item was up to 59% and 34%, respectively. It was also noticed that after a 2-month storage period, the acid value and the peroxide value increased about 7-fold and 2-fold, the oxidative induction time decreased about 2-fold and the percentage shares of fatty acid groups changed. In conclusion, the results obtained in this research indicate that storage period has a significant impact on avocado pulp oil quality. Full article