Oxidative stability of cold‐pressed rapeseed oil was determined using two accelerated methods—Pressure Differential Scanning Calorimetry (PDSC) and Rancimat. Tests were carried out at six different ...temperatures (90–140°C), and the induction time (PDSC τmax, Rancimat τon) was a result. Based on the induction times, the Arrhenius equation and the activated complex theory, frequency factors (Z), constant reaction rate (k) for all temperatures, activation energies (Ea), Q10 numbers, activation enthalpies (ΔH‡), and activation entropies (ΔS‡) for cold‐pressed rapeseed oils oxidative stability were calculated. The activation energy values of rapeseed oil oxidation in PDSC and Rancimat method ranged from 86.71 to 90.54 kJ mol−1 and from 75.73 to 77.64 kJ mol−1, respectively. The Q10, ΔH‡, and ΔS‡ values for analyzed rapeseed oil were between 2.00 and 2.07, 83.48 and 87.31 kJ mol−1, −61.30 and −51.40 J molK−1 calculated for PDSC measurements, and from 1.84 to 1.86, 72.50 to 74.41 kJ mol−1, −66.30 to −60.84 J molK−1 for Rancimat measurements, respectively.
Practical applications: This research present the differences in the oxidative stability of cold‐pressed rapeseed oil using PDSC and Rancimat method. The results of the PDSC test may be recommended as an appropriate objective method for assessing the oxidative stability of cold‐pressed rapeseed oil. Also, results of kinetic oxidation parameters may be helpful to predicting the oil oxidative stability at different temperatures of oxidation process.
The study evaluate the oxidative stability of cold‐pressed rapeseed oils using Pressure Differential Scanning Calorimetry (PDSC) and Randimat method. The research shows a correlation (r = 0.9975) between two accelerated methods (PDSC and Rancimat) of assessing lipid oxidative stability.
The study evaluate the oxidative stability of cold‐pressed rapeseed oils using Pressure Differential Scanning Calorimetry (PDSC) and Randimat method. The research shows a correlation (r = 0.9975) between two accelerated methods (PDSC and Rancimat) of assessing lipid oxidative stability.
Due to the inconsistency of monoacylglycerols’ (MAGs) impacts and the lack of research concerning the weight of saturated monoacylglycerols on the oxidative stability of oils, the current study was ...designed. For this purpose, saturated MAGs at 0.5, 3.0 and 5.0% were added to canola oil and subsequently exposed to a Schaall oven test at 60 °C for 31 days (to assimilate moderate thermal conditions and a prolonged treatment time) and a Rancimat test at 110 °C (to assimilate extreme thermal conditions and shorter treatment time). To evaluate the quality and oxidative stability parameters of MAG-containing canola oil, free fatty acids (FFA), peroxide value (PV), and the oxidative stability index (OSI) were determined. The findings indicated that with the increase in MAG levels, the FFA increased from 0.05 up to 0.2%. The PV increased from 2 to 100 meq/L with the increase in MAG concentration. Also, it was shown that OSI increased from 12.20 to 13.10 h, which was proportional to MAG concentration.
In this study, the effects of roasting camellia (Camellia oleifera Abel.) seed oils at different temperatures (65°C, 100°C, 120°C, and 140°C) on the oxidative stability and composition of the oils ...were investigated. The results showed that, in terms of the quality of the oils, the roasting temperature influenced the total phenolic content (which ranged from 1.64～2.45 GAE mg/g for the different oils) and total flavonoid content (which ranged from 0.36～0.45 QE mg/g for the different oils), while the fatty acid profile and tocopherol content were not influenced by the roasting temperature. We also investigated the kinetic parameters of camellia seed oil during oxidation via Rancimat (at temperatures ranging from 110~140°C). It turned out that the natural logarithms of the oxidative stability index (OSI) varied linearly with respect to temperature (R2: 0.958～0.997). This was done on the basis of the Arrhenius equation that indicates that the activation energies (Ea) for oxidative stability are 65.7～78.4 KJ/mol. Simultaneously, we found that increasing the roasting temperature could increase the antioxidant stability of Maillard reaction products in camellia seed oil. The effects of roasting include the assurance that the camellia seed oil so produced will comply with the relevant governmental health codes and standards and have a longer shelf life.
One of the commonly used food preparation methods is frying. Fried food is admired by consumers due to its unique taste and texture. Deep frying is a process of dipping food in oil at high ...temperature, usually 170-190 °C, and it requires a relatively short time. The aim of this study was to analyze the thermo-oxidative changes occurring during the deep frying of products such as potatoes and tofu in cold pressed rapeseed oils and palm olein. Cold pressed rapeseed oil from hulled seeds (RO), cold pressed high oleic rapeseed oil from hulled seeds (HORO), and palm olein (PO) (for purposes of comparison) were used. Characterization of fresh oils (after purchase) and oils after 6, 12, and 18 h of deep frying process of a starch product (potatoes) and a protein product (tofu) was performed. The quality of oils was analyzed by determining peroxide value, acid value, p-anisidine value, content of carotenoid and chlorophyll pigments, polar compounds, smoke point, color (CIE L*a*b*), fatty acids content and profile, calculation of lipid nutritional quality indicators, and oxidative stability index (Rancimat). Cold pressed high oleic rapeseed oil was more stable during deep frying compared to cold pressed rapeseed oil, but much less stable than palm olein. In addition, more thermo-oxidative changes occurred in the tested oils when deep frying the starch product (potatoes) compared to the deep frying of the protein product (tofu).
Besides affecting the oil’s sensorial characteristics, the presence of herbs and spices has an impact on the nutritional value of the flavored oils. The aim of the study was to develop a new product ...based on the phenol-enrichment of a virgin olive oil with both its own phenolic compounds (secoiridoid derivatives) plus additional complementary phenols from thyme (flavonoids). We studied the effect of the addition of phenolic extracts (olive cake and thyme) on phenolic composition, oxidative stability, antioxidant activity, and bitter sensory attribute of olive oils. Results showed that flavonoids from thyme appeared to have higher transference ratios (average 89.7%) from the phenolic extract to oil, whereas secoiridoids from olive presented lower transference ratios (average 35.3%). The bitter sensory attribute of the phenol-enriched oils diminished with an increase of the concentration of phenols from thyme, which might denote an improvement in the consumer acceptance.
Polyphenols are present in many plants and herbs, and the scientific community and consumers are aware of their health-promoting effects. Plants of Greek origin were studied for their polyphenol ...content and their antioxidant and antimicrobial activities. Gas chromatography–mass spectrometry (GC–MS) and high-performance liquid chromatography coupled to a diode array detector (HPLC–DAD) were used for the identification and characterization of plant polyphenols. For GC–MS, a silylation procedure was employed. Ferulic acid, quercetin, and catechin were the most abundant polyphenols. The Rancimat test, FRAP (Ferric-reducing Antioxidant power) assay, and DPPH (2,2-Diphenyl-1-picrylhydrazyl) assay were used to study the antioxidant capacity, which was proven for all studied plants. The antimicrobial activity was studied against specific pathogenic microorganisms. Pelargonium purpureum and Sideritis scardica plant extracts inhibited most microorganisms such as L. monocytogenes and E. coli. Extracts of studied plants showed both antioxidant and antimicrobial activities; hence, they can be considered to be used by the food industry.
Different biological sources of
-3 polyunsaturated fatty acids (
-3 PUFA) in mainstream commercial products include algae and fish. Lipid oxidation in
-3 PUFA-rich oil is the most important cause of ...its deterioration. We investigated the kinetic parameters of
-3 PUFA-rich oil during oxidation via Rancimat (at a temperature range of 70~100 °C). This was done on the basis of the Arrhenius equation, which indicates that the activation energies (
a) for oxidative stability are 82.84-96.98 KJ/mol. The chemical substrates of different oxidative levels resulting from oxidation via Rancimat at 80 °C were evaluated. At the initiation of oxidation, the tocopherols in the oil degraded very quickly, resulting in diminished protection against further oxidation. Then, the degradation of the fatty acids with
-3 PUFA-rich oil was evident because of decreased levels of PUFA along with increased levels of saturated fatty acids (SFA). The quality deterioration from
-3 PUFA-rich oil at the various oxidative levels was analyzed chemometrically. The anisidine value (p-AV, r: 0.92) and total oxidation value (TOTOX, r: 0.91) exhibited a good linear relationship in a principal component analysis (PCA), while oxidative change and a significant quality change to the induction period (IP) were detected through an agglomerative hierarchical cluster (AHC) analysis.
Hyaluronic acid (Hyaluronan, HA) was depolymerised by gamma irradiation and its structural changes and antioxidant activities were investigated. The structural changes of gamma irradiated HA were ...studied by gel-permeation chromatography (GPC), viscosity, pH, Hunter colour measurement, UV spectrophotometry, and FT-IR spectroscopy. The results demonstrated that gamma irradiation decreased molecular weight size, viscosity and pH of the hyaluronic acid and its colour turned to intense yellow. UV spectra of the irradiated HA showed a change at 265nm, which indicates the formation of double bonds. Differences in the height and shape of certain absorption bonds of FT-IR spectra in the range 1700–1750cm−1 were also observed, which is associated with the formation of carboxylic acid. From these structural changes of the HA, gamma irradiation may have a role in the formation of pyrancarboxylic acid rings. DPPH radical scavenging ability and the reducing power of gamma irradiated HA were significantly higher than that of non-irradiated HA. However, non-irradiated and irradiated HA did not show significant differences in the Rancimat test.
Ferulic acid (FA) is a naturally occurring phenolic antioxidant that is widely used in the food, pharmaceutical, and cosmetic industries due to its low toxicity. Its derivatives also find numerous ...industrial applications and may have even higher biological activity than ferulic acid. In this study, the effect of the addition of FA and its derivatives-including vanillic acid (VA), dihydroferulic acid (DHFA), and 4-vinylguaiacol (4-VG)-on the oxidative stability of cold-pressed flaxseed oil and the degradation of bioactive compounds during oxidation was investigated. The results showed that FA and its derivatives affected the oxidative stability of flaxseed oil, but their antioxidant activity depended on the concentration (25-200 mg/100 g oil) and temperature of treatment (60-110 °C). Based on Rancimat test results, flaxseed oil oxidative stability predicted at 20 °C increased linearly with ferulic acid concentration, while its derivatives effectively prolonged the induction time at lower concentrations (50-100 mg/100 g oil). The addition of phenolic antioxidants (80 mg/100 g) generally showed a protective effect against polyunsaturated fatty acids (DHFA and 4-VG), sterols (4-VG), tocols (DHFA), squalene, and carotenoids (FA). The exception was VA, which increased the degradation of most bioactive compounds. It is believed that adding properly composed mixtures of FA and its derivatives (DHFA and 4-VG) can extend the shelf life of flaxseed oil and provide nutritional benefits.
Supercritical fluid extraction (SFE) of the volatile oil from Thymus vulgaris L. aerial flowering parts was performed under different conditions of pressure, temperature, mean particle size and CO₂ ...flow rate and the correspondent yield and composition were compared with those of the essential oil isolated by hydrodistillation (HD). Both the oils were analyzed by GC and GC-MS and 52 components were identified. The main volatile components obtained were p-cymene (10.0-42.6% for SFE and 28.9-34.8% for HD), γ-terpinene (0.8-6.9% for SFE and 5.1-7.0% for HD), linalool (2.3-5.3% for SFE and 2.8-3.1% for HD), thymol (19.5-40.8% for SFE and 35.4-41.6% for HD), and carvacrol (1.4-3.1% for SFE and 2.6-3.1% for HD). The main difference was found to be the relative percentage of thymoquinone (not found in the essential oil) and carvacryl methyl ether (1.0-1.2% for HD versus t-0.4 for SFE) which can explain the higher antioxidant activity, assessed by Rancimat test, of the SFE volatiles when compared with HD. Thymoquinone is considered a strong antioxidant compound.
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