Isoflavones Play a Potential Role in Off-Flavour Scavenging, with a Key Role of IFS2 in Isoflavone Accumulation in Soybean Seeds.

Research background: Soybean (Glycine max (L.) Merr) is a nutrient-rich crop with a high protein content and various bioactive compounds with health-promoting properties. Nevertheless, it is poorly accepted as a food by consumers due to its off-flavour. Due to the ubiquitous presence of isoflavones in soybeans, their inherent antioxidant potential and inhibitory effect on lipoxygenase activity, their sensory properties are currently being considered to mitigate the off-flavour. Experimental approach: In the present study, the content and composition of isoflavones in 17 soybean cultivars are determined. The correlation between the isoflavone mass fraction and lipid peroxidation was also established, using thiobarbituric acid (TBA) value and carbonyl compound concentration as indices for the development of off-flavour. Cloning, gene expression analysis and in silico analysis of isoflavone synthase isoforms (IFS1 and IFS2) were also performed. Results and conclusions: The total isoflavone mass fraction in soybean genotypes ranged from (153.5±7.2) µg/g for PUSA 40 to (1146±43) µg/g for Bragg. There was a moderately negative correlation between the indices of off-flavour formation and the genistein/daidzein ratio (p<0.1). However, the correlation with total isoflavone mass fraction was found to be insignificant, indicating complex interactions. Higher protein-protein interactions for the predicted structure of IFS2 with other biosynthesis enzymes and its comparatively higher expression in the Bragg than that of IFS1 indicated its more important role in isoflavone synthesis. Novelty and scientific contribution: The genistein/daidzein mass ratio was found to be an important factor in controlling off-flavour. IFS2 was identified as key to produce soybeans with high isoflavone mass fraction and potentially lower off-flavour formation.

Quality Assessment of Deep-Frying Palm Oil by Impedimetric Sensing with a Simple and Economic Electrochemical Cell.

Quality control of deep-frying oil is a global public health concern. A simple and economic electrochemical chamber composed of two bare screen-printed carbon electrodes (working area: 78.54 × 102 cm2; distance: 0.0055 cm; cell constant: 0.70 × 10-2 cm-1) was constructed for precisely acquiring the impedimetric responses of a high-resistance palm oil sample (RSD < 7%, n = 3). Good correlations between the measured impedance data (charge transfer resistance and logarithmic output impedance (Log Z) obtained in the frequency region <0.1 Hz) and the regulatory quality indicators (total polar compounds and acid value) were achieved (R2 > 0.97), suggesting that the proposed impedimetric sensing method is useful for accurately assessing the deteriorated condition of repeated frying oil. Applications for rapid screening can also be realized because the measurement times of Log Z at any given perturbation frequency from 0.01-1 Hz were all less than 3 min.

Assessment of Agroeconomic Indicators of Sesamum indicum L. as Influenced by Application of Boron at Different Levels and Plant Growth Stages.

To achieve the nutritional target of human food, boron (B) has been described as an essential mineral in determining seed and theoretical oil yield of Sesamum indicum L. The research to increase its cultivation is garnering attention due to its high oil content, quality and its utilization for various purposes, which include human nutrition as well as its use in the food industry. For this, a two-year field experiment was performed at PAU, Punjab, India to determine the effect of different concentrations of foliar-applied B (20, 30 and 40 mg L-1) and different growth stages of crop, i.e., we measured the effects on agroeconomic indicators and certain quality parameters of sesame using different concentrations of B applied at the flowering and capsule formation stages as compared to using water spray and untreated plants. Water spray did not significantly affect the studied parameters. However, B application significantly increased the yield, uptake, antioxidant activity (AOA) and theoretical oil content (TOC) compared to those of untreated plants. The maximum increase in seed yield (26.75%), B seed and stover uptake (64.08% and 69.25%, respectively) as well as highest AOA (69.41%) and benefit to cost ratio (B:C ratio 2.63) was recorded when B was applied at 30 mg L-1 at the flowering and capsule formation stages. However, the maximum sesame yield and B uptake were recorded when B was applied at a rate of 30 mg L-1. A significant increase in TOC was also recorded with a B application rate of 30 mg L-1. For efficiency indices, the higher values of boron agronomic efficiency (BAE) and boron crop recovery efficiency (BCRE) were recorded when B was applied at 20 mg L-1 (5.25 and 30.56, respectively) and 30 mg L-1 (4.96 and 26.11, respectively) at the flowering and capsule formation stages. In conclusion, application of B @ 30 mg L-1 at the flowering and capsule formation stages seemed a viable technique to enhance yield, B uptake and economic returns of sesame.

[Change pattern and correlation analysis of macroscopic characteristics, active components and rancidness degrees of Armeniacae Semen Amarum in deterioration process].

To discuss the effect of deterioration on the quality of Armeniacae Semen Amarum by observing the changes of macroscopic characteristics, active components and rancidness degrees of Armeniacae Semen Amarum in deterioration process. The traditional macroscopic identification was used to observe, identify and classify the morphologic and organleptic characteristics of Armeniacae Semen Amarum. The contents of amygdalin and fatty oil(two representatives of active components) were detected by HPLC and general rule 0713 in Chinese Pharmacopoeia, respectively. Acid value and peroxide value of the samples were selected as the representative indices of different rancidness degrees, and the general rule 2303 was adopted as the method for quantitative analysis. Then principal component analysis(PCA), partial least square analysis discrimination analysis(PLS-DA) were further utilized to establish the discriminative models of samples with different rancidness degrees, and also to screen out the largest contribution factors. In sensory evaluation, Armeniacae Semen Amarum samples were divided into three groups: non-rancid, slightly-rancid, and noticeably-rancid. The color of seed coat, cotyledon and surface of noticeably-rancid samples was deepened, and the odor differed much from non-rancid samples. Average content of amygdalin and fatty oil in non-rancid samples was 4.12% and 67.77%, respectively, both meeting the requirements of Chinese Pharmacopoeia; and decreased to some extent in slightly-rancid samples. However, the content of amygdalin sharply dropped to 0.074% in noticeably-rancid samples. The acid value and peroxide value were increased significantly with the intensifying of the rancidness degree, from only 1.363 and 0.016 74 in non-rancid samples to 1.865 and 0.023 70 in slightly-rancid samples, even doubled in noticeably-rancid samples(2.167 and 0.033 82). The discriminative models established by PCA and PLS-DA could complete the task of distinguishing the non-rancid samples from noticeably-rancid ones. The contribution degree of amygdalin content as one of the input attributes of discriminative model was higher than 1. Rancidness affected the quality of Armeniacae Semen Amarum, resulting in appearance changes, decrease in content of active components, and increase in acid value and peroxide value. Obviously, noticeably-rancid samples were non-conforming to Chinese Pharmacopoeia and no longer suitable for medicinal use. Rancidness can significantly reduce the quality of Armeniacae Semen Amarum, and even could possibly produce toxicity, which should attach more attention.

Effect of ultrasound dielectric pretreatment on the oxidation resistance of vacuum-fried apple chips.

BACKGROUND: In order to investigate the effect of ultrasound dielectric pretreatment on the oxidation resistance of vacuum-fried apple chips, apple slices were pretreated at ultrasonic powers of 150, 250 and 400 W for times of 10, 20 and 30 min before vacuum frying. The quality and oxidation resistance of fried apple were evaluated by testing the dielectric properties and comparing the moisture content, oil uptake, color, acid value (AV) and peroxide value (PV) of apple chips. RESULTS: Ultrasonic treatment significantly changed the dielectric properties of apple slices. Moisture and oil contents of apple chips decreased with increasing ultrasonic power and time. During storage, the color retention of fried apple chips processed by ultrasound was improved. AV and PV values of fried apple chips processed by ultrasound were lower, which improved their antioxidant properties. CONCLUSION: The results of the present study indicated that ultrasound dielectric pretreatment improved not only the quality of vacuum-fried apple chips but also their antioxidant properties. © 2018 Society of Chemical Industry.

Antioxidant (Tocopherol and Canolol) Content in Rapeseed Oil Obtained from Roasted Yellow-Seeded Brassica napus.

In this study, the effect of temperature (140, 160, 180 °C) and roasting time (5, 10, 15 min) on the bioactive compound content (canolol, tocopherol and plastochromanol-8) of cold-pressed oil from yellow-seeded rapeseed lines of different colors was investigated. Roasting increased the peroxide value in the seed oils compared to the oils from the control samples. However, roasting did not affect the acid values of the oils, which were 1.15-1.47 and 1.30-1.40 mg KOH/g, for line PN1 03/1i/14 (yellow seeds) and line PN1 563/1i/14 (brown seeds), respectively. In this study, the seeds of line PN1 03/1i/14 were characterized by different changes in canolol content during roasting than the seeds of PN1 563/1i/14. There was a 90-fold increase in canolol for the line PN1 03/1i/14 (768.26 µg/g) and a 46-fold increase for the line PN1 563/1i/14 (576.43 µg/g). Changes in tocopherol and PC-8 contents were also observed. There was an increase in the contents of γ-T and PC-8 in the oils obtained from the seeds roasted at 180 °C for 10 and 15 min. γ-T content increased by 17-18% after 15 min of roasting, whereas the PC-8 content increased twofold.

Development of a process for the manufacture of shelf stable dhal and its physico-chemical properties.

Thermally processed, ready-to consume dhal with natural sensory attributes was developed. Product optimization was done using two variables, retort process time and ratio of water to dhal. Dhal were packed in retortable pouches and processed in a stationary air-steam retort. The product was characterized by a short lag period for the heating curve, j h (0.52-0.64), small heating rate index, f h (3.9-6.5 min) and a short lag factor for the cooling curve, j c (0.53-0.73) implying essentially convective heating regime. The total process time (B') was 11.56-40.25 min for F o value of 2.30-27.30 min. Process time of 25 min at 121 °C and ratio of water to dhal of 2.5 yielded a product that was microbiologically safe as well as sensorily acceptable. During storage, chemical parameters like thiobarbituric acid and free fatty acid increased, while pH decreased with concomitant decrease in sensory scores. Textural properties like, consistency, cohesiveness and index of viscosity underwent a significant (P < 0.05) increase during the storage.

Improvement of efficiency of oil extraction from wild apricot kernels by using enzymes.

An experiment was conducted to evaluate and standardize the protocol for enhancing recovery of oil and quality from cold pressed wild apricot kernels by using various enzymes. Wild apricot kernels were ground into powder in a grinder. Different lots of 3 kg powdered kernel were prepared and treated with different concentrations of enzyme solutions viz. Pectazyme (Pectinase), Mashzyme (Cellulase) and Pectazyme + Mashzyme. Kernel powder mixed with enzyme solutions were kept for 2 h at 50(±2) °C temperature for enzymatic treatment before its use for oil extraction through oil expeller. Results indicate that use of enzymes resulted in enhancement of oil recovery by 9.00-14.22 %. Maximum oil recovery was observed at 0.3-0.4 % enzyme concentration for both the enzymes individually, as well as in combination. All the three enzymatic treatments resulted in increasing oil yield. However, with 0.3 % (Pectazyme + Mashzyme) combination, maximum oil recovery of 47.33 % could be observed against were 33.11 % in control. The oil content left (wasted) in the cake and residue were reduced from 11.67 and 11.60 % to 7.31 and 2.72 % respectively, thus showing a high increase in efficiency of oil recovery from wild apricot kernels. Quality characteristics indicate that the oil quality was not adversely affected by enzymatic treatment. It was concluded treatment of powdered wild apricot kernels with 0.3 % (Pectazyme + Mashzyme) combination was highly effective in increasing oil recovery by 14.22 % without adversely affecting the quality and thus may be commercially used by the industry for reducing wastage of highly precious oil in the cake.

Effect of amurca on olive oil quality during storage.

Total phenolic compounds (TPC), antioxidant activity (AA), lipid peroxidation inhibition (percent) (LPOIP), free fatty acid and peroxide values were measured in olive oil samples over the period of 12 months in comparison with oil samples extracted from amurca (olive oil lees) and olive oil samples taken from the bottom of the canister (near amurca) after 12 months of storage. Olive oil samples taken over the period of 12 months possessed decreasing amounts of TPC, AA and LPOIP, which led to increased peroxide and free fatty acid values. In contrast, oil extracted from amurca and olive oil samples taken from the bottom of the container after 12 months of storage possessed significantly higher TPC, AA, LPOIP and consequently lower free fatty acid and peroxide values. These results show that the presence of naturally occurring amurca (sediment) in stored olive oil stabilizes olive oil quality during storage.

A novel method for determination of peroxide value and acid value of extra-virgin olive oil based on fluorescence internal filtering effect correction.

Peroxide value (PV) and acid value (AV) are widely used indicators for evaluating oxidation degree of olive oils. Fluorescence spectroscopy has been extensively studied on the detection of oil oxidation, however, the detection accuracy is limited due to internal filtering effect (IFE). Due to the primary and secondary IFE, at least two wavelengths of absorption information are required. Least squares support vector regression (LSSVR) models for PV and AV were established based on two absorption coefficients (µa) at 375 nm and emission wavelength and one fluorescence intensity at corresponding wavelength. The regression results proved that the model based on 375 and 475 nm could reach the best performance, with the highest correlation coefficient for prediction (rp) of 0.889 and 0.960 for PV and AV respectively. Finally, the explicit formulations for PV and AV were determined by nonlinear least squares fitting, and the rp could reach above 0.94 for two indicators.

Comparative evaluation of physicochemical and antimicrobial properties of rubber seed oil from different regions of Bangladesh.

In Bangladesh, the annual production of rubber seeds is typically left untapped although the seeds contained a high percentage of oil but underutilized without any value-added utilization. This study aims to evaluate the geographical effect on physicochemical properties, fatty acid composition and the antimicrobial activity of oil extracted from rubber seeds. Seeds were collected from three different regions of Bangladesh and the oil was extracted by the soxhlet method using n-hexane as a solvent. Results demonstrated that the geographical regions have some significant effect on the properties of rubber seed oil (RSO). The physicochemical properties of RSO varied from region to region. For example, the percent of yield, higher heating value, and flash point varied from 50.0 to 50.8 %, 31.8-33.3 kJ/g, and 237-245 °C, respectively. The chemical parameters, such as acid value, iodine value, and hydroxyl value varied from 13.3 to 18.2 mg KOH/g, 132-137 g I2/100g, and 47.7-55.8 mg KOH/g, respectively. Chromatographic analysis showed that RSO mainly contains palmitic, linoleic, linolenic, and stearic acid. Regional variations were also seen in the composition of these fatty acids. Most notably, regardless of the rubber seeds collected from various locations, RSO exhibited inhibitory activity against only gram positive bacteria. The zone of inhibition range for different tested gram positive bacteria was 2.33-11.17 mm irrespective of different RSO samples.

Analysis of Fatty Acid Compositions and Acid Values of Krill Oil Supplementary Products from the Korean Market.

In order to provide the qualitative data for the 20 commercially available krill oil supplementary products ,the levels of omega-3 polyunsaturated fatty acids (PUFA) such as docosahexaenoic acid ( DHA) and eicosapentaenoic acid (EPA),fatty acid compositions, and chemical indices, including acid values , of the supplements , were determined . The acid values ranged from 7.4 to 43 .7 mg of potassium hydroxide (KOH)/ g of oil. The relative percentages of EPA andDHA in the oils ranged from 14.2 to 34.8 % (w/w).Although all 20 krill oil supplements used 100% krill oil as raw material,the fatty acid composition of 4 samples differed from typical krill oil in terms ofthe content of myristic acid (C14:0), palmitic acid (C16:0), palmitoleic acid (C16:1), linoleic acid (C18:2, n-6), and eicosenoic acid (C20:1, n-9). Accordingly, the Ministry of Food and Drug Safety recently standardized linoleic acid (3% orless) and myristic acid (5-13%) as part ofthe fatty acid components of krill oil. This study provides a reference for analyzing the chemical and nutritional properties and evaluating the adulteration of krill oil supplements in theKorean market.

High-Oleic Sunflower Oil as a Potential Substitute for Palm Oil in Sugar Coatings-A Comparative Quality Determination Using Multispectral Imaging and an Electronic Nose.

Palm oil has a bad reputation due to the exploitation of farmers and the destruction of endangered animal habitats. Therefore, many consumers wish to avoid the use of palm oil. Decorative sugar contains a small amount of palm oil to prevent the sugar from melting on hot bakery products. High-oleic sunflower oil used as a substitute for palm oil was analyzed in this study via multispectral imaging and an electronic nose, two methods suitable for potential large-batch analysis of sugar/oil coatings. Multispectral imaging is a nondestructive method for comparing the wavelength reflections of the surface of a sample. Reference samples enabled the estimation of the quality of unknown samples, which were confirmed via acid value measurements. Additionally, for quality determination, volatile compounds from decorative sugars were measured with an electronic nose. Both applications provide comparable data that provide information about the quality of decorative sugars.

Decreasing acid value of fatty acid ethyl ester products using complex enzymes.

Recently, enzymatic method has been used to prepare biodiesel using various oils. But the high acid value of the biodiesel product using enzyme as a catalyst has been one issue. In this work, an attempt to reduce the acid value of fatty acid ethyl ester (FAEE) product to satisfy the specified requirement (AV ≤ 0.5 mgKOH/g), a complex enzyme-catalyzed method was used for the ethanolysis of Semen Abutili seed oil (SASO) (AV = 5.5 ± 0.3 mgKOH/g). The effects of various variables (constituents of complex enzyme, type and addition of water removal agent, time, temperature, enzyme addition load, substrate ratio) on the enzymatic reaction were investigated. The optimal reaction conditions were: 1% addition of liquid lipase Eversa® Transform 2.0% and 0.8% of enzyme dry powder CALB, reaction temperature 35°C, alcohol-oil ratio 9:1 (mol/mol), 0.8 g/g of 4A-MS and reaction time 24 h. Under the optimal reaction conditions, the FAEE yield was 90.8% ± 1.5% and its acid value was decreased from 12.0 ± 0.2 mgKOH/g to 0.39 ± 0.10 mgKOH/g. In further evaluating the feasibility of preparing FAEE from SASO, the FAEE products obtained under the optimal reaction conditions were purified and evaluated with reference to the ASTM D6751 standard for the main physicochemical indexes. The results obtained were in accordance with the requirements except for the oxidative stability.

Preparation and characterisation of kaempferol composite carrier solid dispersion: evaluation of its application in preventing soybean oil spoilage.

Kaempferol (KPF) can be used as a natural antioxidant and food additive in food processing. However, the poor solubility of KPF limited its bioavailability and application. In order to improve the solubility of KPF, kaempferol composite carrier solid dispersion (KPF-CC-SD) was prepared and the process was optimised. When the ratio of KPF: CA (citric acid): Soluplus reached 1:4:6, the dissolution rate was the highest, and the sample was stable over 12 weeks. The characterisation results indicated that KPF-CC-SD exists in an amorphous form. Peroxidation value and acid value of soybean oil showed that the preservation effect of KPF-CC-SD was better than that of KPF, and the inhibition effect of KPF-CC-SD on acid value was better than that of butylated hydroxytoluene. In conclusion, KPF-CC-SD can change the solubility, crystal form and spatial stability of KPF through the carrier, which has a great application prospect in the field of food preservation.

CsPbBr3 NCs Confined and In Situ Grown in ZIF-8: A Stable, Sensitive, Reliable Fluorescent Sensor for Evaluating the Acid Value of Edible Oils.

Rapidly and sensitively evaluating the acid value (AV) of edible oils is significant to ensuring food quality and safety. Cesium lead bromide perovskite nanocrystals (CsPbBr3 NCs) are an effective candidate for AV detection; however, their instability restricts wide applications. Herein, CsPbBr3@ZIF-8 was prepared by confining and growing CsPbBr3 NCs in situ into zeolitic imidazolate framework-8 (ZIF-8) to improve the stability, and a fluorescence sensor was established to evaluate the AV of edible oils. The results present that CsPbBr3 NCs (below 5 nm) with excellent optical properties were confined and grown in situ in micropores and mesopores of ZIF-8. Meanwhile, CsPbBr3@ZIF-8 had better long-term storage, ultraviolet-irradiation, and water-exposure stabilities, compared with CsPbBr3 NCs. Given the fact that free fatty acids (the major contributor of AV) decrease the fluorescence of CsPbBr3 NCs, the fluorescence intensities of CsPbBr3@ZIF-8 were negative-linearly related to oil AV (R2 = 0.9902) in 0.04-6.00 mg of KOH/g with a 0.06 mg of KOH/g limit of detection. Besides, the practical AV recovery was 92-101% with an average relative standard deviation of 2%. Furthermore, the detection time was 20 min. The response mechanism revealed that free fatty acids could remove surface ligands and increase surface defects to prompt the aggregation of CsPbBr3 NCs and the formation of lattice fringe dislocations, inducing a decrease in the fluorescence. Thus, a stable, sensitive, reliable sensor was established to evaluate the AV of edible oils.

Spectroscopic studies on thermal degradation and quantitative prediction on acid value of edible oil during frying by Raman spectroscopy.

The health risks posed by harmful substances resulting from the thermal degradation of frying oils are of great concern. Characteristic peak intensity ratios (PIRs) screened from Raman spectra were used to characterize the thermal degradation. High correlation coefficients between PIRs and acid values (AVs) of 0.972 (linear fitting), 0.984 (logarithmic function fitting), and 0.954 (linear fitting) for fried soybean oil, canola oil, and palm oil, were obtained at the PIRs of I1267/I1749, I1267/I1659, and I1267/I1749, respectively. The highly correlated PIRs common to the three oils were determined by Pearson's correlation coefficient combined with heat maps. To accommodate both linear and nonlinear features, a global model for predicting AVs of multi-varieties frying oils was constructed using a least-squares support vector machine algorithm, and the results performed well with a root mean square error of prediction of 0.016 and a ratio of prediction to deviation of 11.351. The whole results demonstrate that Raman spectroscopy could characterize the thermal degradation and has excellent quantitative analysis ability for food control based on AV in frying oils, thus providing a new approach to quality control of frying oils.

Effects of genotype, environment and their interaction on protein and amino acid contents in soybeans.

Soybean [Glycine max (L.) Merr.] is an important source of protein and oil. Genotype, environment and the interaction of genotype × environment influence the protein composition in soybean seeds. The main objectives of this study were to i) study the influence of genotype, environment and their interaction on soybean protein and amino acid contents; ii) evaluate the stability of soybean genotype across various environments, with a focus on soybeans grown in a northern latitude; and iii) identify the correlation between crude protein and critical amino acid value (CAAV). Twenty-three soybean genotypes were grown at four locations in Manitoba, Canada for two years (2018 and 2019). Soybean seeds were analyzed for protein and amino acids (nine essential amino acids and cysteine). The effects of genotype, environment and genotype × environment interaction on all traits were significant (P < 0.05). Genotype and environments explained the main part of variation for all traits. G13 and G15 cultivars performed better in favorable environments (bi > 1), and G22 cultivar showed greater resistance to environmental change. Protein and amino acids responded differently to various environments, but the optimal environments for greater soybean protein and amino acid remains to be established. The CAAV had a negative linear relationship with protein content in soybean (k = -0.17). This work expands our knowledge of the factors impacting the protein quality of soybeans grown in northern latitudes.

Identification of aged-rice adulteration based on near-infrared spectroscopy combined with partial least squares regression and characteristic wavelength variables.

The long-term storage of rice will inevitably be involved in the deterioration of edible quality, and aged rice poses a great threat to food safety and human health. The acid value can be employed as a sensitive index for the determination of rice quality and freshness. In this study, near-infrared spectra of three kinds of rice (Chinese Daohuaxiang, southern japonica rice, and late japonica rice) mixed with different proportions of aged rice were collected. The partial least squares regression (PLSR) model with different preprocessing was constructed to identify the aged rice adulteration. Meanwhile, a competitive adaptive reweighted sampling (CARS) algorithm was used to extract the optimization model of characteristic variables. The constructed CARS-PLSR model method could not only reduce greatly the number of characteristic variables required by the spectrum but also improve the identification accuracy of three kinds of aged-rice adulteration. As above, this study proposed a rapid, simple, and accurate detection method for aged-rice adulteration, providing new clues and alternatives for the quality control of commercial rice.

Thermal Degradation of Vegetable Oils.

Vegetable oils provide lipids and nutrition and provide foods with a desirable flavor, color, and crispy texture when used to prepare fried foods. However, the oil quality is degraded at elevated temperatures, and thus must be examined frequently because of the damage to human health. In this study, sunflower, soybean, olive, and canola oils were examined, and their properties were measured periodically at different elevated temperatures. The unsaturated triglyceride in oils reacted with the environmental oxygen or water vapor significantly changes in optical absorbance, viscosity, electrical impedance, and acid value. We used defect kinetics to analyze the evolution of these oil properties at elevated temperatures. The optical absorbance, viscosity, and electrical impedance follow the second-order, first-order, and zeroth-order kinetics, respectively. The rate constants of the above kinetics satisfy the Arrhenius equation. Olive oil has the lowest rate of color center and dynamic viscosity among the four oils, with the smallest pre-exponential factor and the largest activation energy, respectively. The rate constants of acid reaction also satisfy the Arrhenius equation. The activation energies of the polar compound and acid reaction are almost the same, respectively, implying that the rate constant is controlled by a pre-exponential factor if four oils are compared. Olive oil has the largest rate constant of acid reaction among the four oils, with the lowest pre-exponential factor.