Migrated phthalate levels into edible oils

The determination of phthalates in edible oils (virgin olive oil, olive oil, canola oil, hazelnut oil, sunflower oil, corn oil) sold in Turkish markets was carried out using gas chromatography–mass spectrometry. Mean phthalate concentrations were between 0.102 and 3.863 mg L^?1 in virgin olive oil; 0.172 and 6.486 mg L^?1 in olive oil; 0.501 and 3.651 mg L^?1 in hazelnut oil; 0.457 and 3.415 mg L^?1 in canola oil; 2.227 and 6.673 mg L^?1 in sunflower oil; and 1.585 and 6.248 mg L^?1 in corn oil. Furthermore, the influence of the types of oil and container to the phthalate migration was investigated. The highest phthalate levels were measured in sunflower oil. The lowest phthalate levels were determined in virgin olive oil and hazelnut oil. The highest phthalate levels were determined in oil samples contained in polyethylene terephthalate.     

QUANTITATIVE ANALYSIS OF FAT AND MOISTURE IN MAYONNAISE USING FOURIER TRANSFORM INFRARED SPECTROMETER

ABSTRACT

A rapid method for quantitative determination of fat and moisture in a variety of mayonnaise products (regular, reduced- and low-fat) was developed using Fourier Transform Infrared (FTIR) spectroscopy. Both the fat and moisture contents could be effectively solvated out of the soluble solids using 1-propanol without sonication. A load cell assembly with a 100 mm Teflon spacer gave sufficient separation under 2 cm^?1 resolution using 100 scans. Two distinct peaks were obtained on the ratioed sample spectra of regular mayonnaise: 1748 cm^?1 and 1650 cm^?1 for C?O stretching of oil and H-O-H bending of water, respectively. Data was then normalized using the Window-based software that acquired spectra information seamlessly from the instrument. The experimental measurements of the fat and moisture contents were in excellent agreement with those using the modified Mojonnier and the dehydration method, respectively. The method was accurate over all varieties of mayonnaise studied (p < 0.05).     

Single-laboratory validation of a saponification method for the determination of four polycyclic aromatic hydrocarbons in edible oils by HPLC-fluorescence detection

An analytical method is reported for the determination of four polycyclic aromatic hydrocarbons (benzo[a]pyrene (BaP), benz[a]anthracene (BaA), benzo[b]fluoranthene (BbF) and chrysene (CHR)) in edible oils (sesame, maize, sunflower and olive oil) by high-performance liquid chromatography. Sample preparation is based on three steps including saponification, liquid–liquid partitioning and, finally, clean-up by solid phase extraction on 2 g of silica. Guidance on single-laboratory validation of the proposed analysis method was taken from the second edition of the Eurachem guide on method validation. The lower level of the working range of the method was determined by the limits of quantification of the individual analytes, and the upper level was equal to 5.0 µg kg^?1. The limits of detection and quantification of the four PAHs ranged from 0.06 to 0.12 µg kg^?1 and from 0.13 to 0.24 µg kg^?1. Recoveries of more than 84.8% were achieved for all four PAHs at two concentration levels (2.5 and 5.0 µg kg^?1), and expanded relative measurement uncertainties were below 20%. The performance of the validated method was in all aspects compliant with provisions set in European Union legislation for the performance of analytical methods employed in the official control of food. The applicability of the method to routine samples was evaluated based on a limited number of commercial edible oil samples.     

Occurrence of 3-MCPD and glycidyl esters in edible oils in the United States

Fatty acid esters of 3-monochloropropanediol (3-MCPD) and glycidol are processing contaminants found in a wide range of edible oils. While both 3 MCPD and glycidol have toxicological properties that at present has concerns for food safety, the published occurrence data are limited. Occurrence information is presented for the concentrations of 3-MCPD and glycidyl esters in 116 retail and/or industrial edible oils and fats using LC-MS/MS analysis of intact esters. The concentrations for bound 3-MCPD ranged from below the limit of quantitation (<LOQ) to 0.09 mg kg^?1 (ppm) in 22 unrefined oils and from 0.005 to 7.2 mg kg^?1 (ppm) in 94 refined oils. The concentrations for bound glycidol ranged from <LOQ to 0.03 mg kg^?1 (ppm) in unrefined oil samples and from <LOQ to 10.5 mg kg^?1 (ppm) in processed oil samples. The highest concentrations for both 3-MCPD and glycidol were seen in refined palm oil and palm olein samples. Palm olein samples also contained a higher percentage of 3-MCPD in mono-ester form than any other type of oil.     

A New Method for Determining Free Fatty Acid Content in Edible Oils by Using Electrical Conductivity

In the current study, a new method for determining free fatty acid (FFA) content in edible oils has been developed based on the electrical conductivity (EC) value change of a 0.04 M potassium hydroxide (KOH) solution during KOH–FFA mixed reaction. At ambient temperature, 4.000?±?0.001 g of edible oils (oils with a high melting point were melted first) was dispersed in 40.0?±?0.1 ml of KOH solution. The mixtures were stirred for 5 s and were held for 5 min. The EC value changes of the KOH solution layers were determined, and the FFA was predicted basing on the calibration. The analytical conditions studied include the concentration of KOH solution, holding time, the types of edible oils, setting temperature, and the ratio of oil to KOH solution (m/v). The calibration was validated by using the American Oil Chemists’ Society (AOCS) titrimetric FFA method. The analytical conditions were found to have no significant effects on the results. When the ratio of oil to KOH solution was 1:10 (m/v), the calibration was y?=?12.04x?0.0769 (where x is the EC value change and y is the FFA content), R?=?0.9992, SD?=?0.0745, and a calibration with an SE of <0.0745 % FFA over a range of 0 % to 5 % was obtained. The method was validated using standard addition and the AOCS method. The results show that the analytical performance of the EC procedure is as good as or better than that of the AOCS titrimetric procedure.     

Antimicrobial Effect of Edible Coating Blend Based on Turmeric Starch Residue and Gelatin Applied onto Fresh Frankfurter Sausage

The microbial and physicochemical properties of edible coating blend based on turmeric starch and bovine gelatin on frankfurter sausage were studied during the product’s shelf life. Three edible films were prepared and their thermal, mechanical, and barrier properties evaluated one with turmeric starch (TF), one with gelatin (GF), and one with a blend of turmeric-starch and gelatin (BF). Physicochemical and bacteriostatic effects of the blend on the sausage were measured. Water vapor permeability (8.01 g day^?1 m^?2 atm^?1) and tensile strength of the BF showed intermediate values (5 MPa) compared with results of the films containing turmeric (5.88 g day^?1 m^?2 atm^?1; 4 MPa) or gelatin (13.4 g d^?1 m^?2 atm^?1; 13 MPa) separately. Tensile strength was higher to GF (13 MPa), lower value (4 MPa) was obtained to TF, and intermediate value to BF (5 MPa). Elastic modulus was lower to BF (85 MPa) when compared to TF (126 MPa) and GF (271 MPa). Elongation at break of BF (42%) was higher among the three edible films (TF 7% and GF 36%). Emulsion stability measured by thermal analysis in DSC showed complete miscibility to BF, observed through melting point of polymers. The effect of the turmeric-gelatin blend coating on sausages stored at 5 and 10 °C showed a significant (p ≥ 0.05) positive effect on decrease of microbial growth over 30 days. Physicochemical characteristics such as pH, texture profile, moisture, and color remained constant compared to control. Thus, the edible coating based on turmeric starch and gelatin blend is an alternative to replace the synthetic casing in frankfurter sausage.     

Determination of free fatty acids in foods by flow injection

A flow injection manifold has been developed for the spectrophotometric determination of free fatty acids (FFA) at 716 nm after continuous extraction into an organic phase of soaps formed by the reaction of copper acetate with the analytes. The carrier system stream was toluene and the reagent stream aqueous copper acetate-pyridine (50 g litre^?1). The calibration graph was linear over the range 1 × 10^?4 to 5 × 10^?3 M oleic acid using an injection volume of 115 μl. The injection rate was 75 samples h^?1 with a precision of 109% (RSD). Though this procedure does not permit the total recovery of short-chain fatty acids it is very effective in reflecting the total concentration of FFA. The system has been applied to the determination of total FFA in olive oil, milk fat and cocoa butter. Although the values obtained by the proposed method are lower than those obtained by the reference method (titration) and by chromatography, their comparison shows good linearity.     

Development of a novel controlled-release nanocomposite based on poly(lactic acid) to increase the oxidative stability of soybean oil

A poly(lactic acid) (PLA)-based nanocomposite active packaging was developed for the controlled release of tert-butylhydroquinone (TBHQ) antioxidant. The PLA-based active films were loaded with only TBHQ (3% wt) or a mixture of modified cellulose nanofibre (MCNF) (8% wt) and TBHQ (3% wt) to obtain active and nanocomposite active films, respectively. Release studies indicated that the release rate of TBHQ in 95% ethanol simulant was significantly decreased by the addition of MCNF. Moreover, the presence of MCNF diminished the increasing effect of temperature on the release rate as when storage temperature increased from 4°C to 40°C. The diffusion coefficient (D) for PLA-TBHQ and PLA-MCNF-TBHQ films increased from 6.75 and 4.34 × 10^?8 cm² s^?1 to 19.85 and 8.49 × 10^?8 cm² s^?1, respectively. Diffusion of TBHQ to soybean oil was enough to delay the induction of the oxidation of soybean oil stored for 6 months in contact with PLA-based films. Antioxidative activity of PLA-based active films considerably increased with increasing storage time as indicated by the increase in 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and the oxidative stability index (p < 0.05). This study demonstrates that effective controlled release antioxidant packaging could be obtained by using MCNF nanofiller, which leads to prolonged activity and an extended shelf-life in fatty foods.     

Application of FTIR Spectroscopy for Monitoring the Stabilities of Selected Vegetable Oils During Thermal Oxidation

Fourier transform infrared spectroscopy has been developed for rapid monitoring of the oxidative stabilities of selected vegetable oils, namely corn oil, rice bran oil, soybean oil, and sunflower oil during thermal treatment at 160°C for 120 h. There were several absorbance changes between non-oxidized and oxidized vegetable oils during thermal oxidation. Peak intensities at 3470, 1655, and 967 cm^?1 were increased; meanwhile peak intensities at 3008 and 722 cm^?1 were decreased. The R² values for the correlation between the absorbance changes at 3008 cm^?1 and the specific absorptivities of conjugated dienes for corn oil, rice bran oil, soybean oil, and sunflower oil were 0.938, 0.845, 0.978, and 0.824, respectively. The absorbance changes of Fourier transform infrared spectra at 3008 cm^?1 were also correlated with the specific absorptivities of conjugated trienes and p-anisidine values with the acceptable R² values. Compared with the conventional technique, the use of Fourier transform infrared spectroscopy for measurement the thermal oxidative stability has some advantages, i.e., it is a rapid technique and no sample preparation. In addition, Fourier transform infrared spectroscopy reduces or eliminates solvents and chemical reagents that are hazardous to human health or to the environment; therefore, Fourier transform infrared spectroscopy can support the campaign of “green analytical chemistry.”     

Antioxidant activity of ginger extract in sunflower oil

The antioxidant activity of dichloromethane extract from ginger was evaluated during 6 months of storage of refined sunflower oil at 25 and 45 °C. Free fatty acid (FFA) content, peroxide value (POV) and iodine value (IV) were used as criteria to assess ginger extract as an antioxidant. After 6 months of storage at 45 °C, sunflower oil containing 1600 and 2400 ppm ginger extract showed lower FFA contents (0.083 and 0.080%) and POVs (24.5 and 24.0 meq kg^?1) than the control sample (FFA contents 0.380%, POV 198.0 meq kg^?1). Sunflower oil containing 200 ppm butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) showed FFA contents of 0.089 and 0.072% and POVs of 26.5 and 24.7 meq kg^?1 respectively after 6 months of storage at 45 °C. Similarly, after 6 months of storage at 45 °C, IVs of sunflower oil containing 1600 and 2400 ppm ginger extract were 80 and 92 respectively, higher than that of the control sample (53). However, IVs of sunflower oil treated with 200 ppm BHA and BHT were 94 and 96 respectively after 6 months of storage at 45 °C. These results illustrate that ginger extract at various concentrations exhibited very strong antioxidant activity, almost equal to that of synthetic antioxidants (BHA and BHT). Ginger extract also showed good thermal stability and exhibited 85.2% inhibition of peroxidation of linoleic acid when heated at 185 °C for 120 min. Therefore the use of ginger extract in foods is recommended as a natural antioxidant to suppress lipid oxidation. © 2003 Society of Chemical Industry     

Determination of benzo[α]pyrene in edible oil using tetraoxocalix[2]arene[2]triazine bonded silica SPE sorbent

Benzo[α]pyrene (BaP) is a well-known carcinogen in edible oil. In this study, a method combined solid-phase extraction (SPE) with fluorescent detection was developed using tetraoxocalix[2]arene[2]triazine sorbent (SiO₂-OCA) for the clean-up and enrichment of BaP. The interaction between SiO₂-OCA and BaP involves a donor–acceptor complex mechanism. The experimental procedure was as follows: BaP was extracted from edible oil with DMF/H₂O (9:1, v/v). Then, the ratio of DMF/H₂O was adjusted to 1:2 prior to SPE. The final concentrate was analysed using a fluorescence detector at excitation and emission wavelengths of 255 and 420 nm. The method was fully validated. The linearity was in the range of 0.1–100 μg kg^?1 with a coefficient of 0.999. The limits of detection and quantification were 0.03 and 0.1 μg kg^?1, respectively. The average recoveries were in the range of 88.0 ? 122.3%. The intraday and interday precisions were 6.8% and 9.2%, respectively. Compared with other methods, the method reported in this article shows a good detection limit, high reproducibility and recovery and linearity over a broad concentration range. This established method was also applied to evaluate real samples. The concentration of six tested samples was below 5 μg kg^?1.     

Effects of Interactions between the Constituents of Chitosan-Edible Films on Their Physical Properties

The main objective of this work was to evaluate the effect of chitosan and plasticizer concentrations and oil presence on the physical and mechanical properties of edible films. The effect of the film constituents and their in-between interactions were studied through the evaluation of permeability, opacity and mechanical properties. The effects of the studied variables (concentrations of chitosan, plasticizer and oil) were analysed according to a 2³ factorial design. Pareto charts were used to identify the most significant factors in the studied properties (water vapour, oxygen and carbon dioxide permeability; opacity; tensile strength; elongation at break and Young’s modulus). When addressing the influence of the interactions between the films’ constituents on the properties above, results show that chitosan and plasticizer concentrations are the most significant factors affecting most of the studied properties, while oil incorporation has shown to be of a great importance in the particular case of transport properties (gas permeability), essentially due to its hydrophobicity. Water vapour permeability values (ranging from 1.62?×?10^?11 to 4.24?×?10^?11 g m^?1 s^?1 Pa^?1) were half of those reported for cellophane films. Also the mechanical properties (tensile strength values from 0.43 to 13.72 MPa and elongation-at-break values from 58.62% to 166.70%) were in the range of those reported for LDPE and HDPE. Based on these results, we recommend the use of 1.5% (w/w) chitosan concentration to produce films, where the oil and plasticizer proportions will have to be adjusted in a case-by-case basis according to the use intended for the material. This work provides a useful guide to the formulation of chitosan-based film-forming solutions for food packaging applications.     

Determination of Iron in Edible Oil by FAAS After Extraction with a Schiff Base

The synthesis of a new Schiff base has been achieved by condensation reaction of 1,3-diamino-2-propanol and 2-hydroxy-5-methoxy-benzaldehyde in alcoholic media. The Schiff base was characterized by elemental analysis, IR, UV–Visible, ¹H-NMR, and ¹³C-NMR spectroscopy and used for the extraction of iron in liquid edible oils. Iron complex with the Schiff base was investigated in order to determine experimental conditions of the complexation. The extraction of iron from oils to aqueous phase was succeeded by the complexation with the Schiff base. A central composite design was employed in order to optimize the extraction conditions of iron. Optimum conditions for the iron extraction with N,N′-bis(5-methoxy-salicylidene)-2-hydroxy-1,3-propanediamine were found to be 19.3 °C, 2.1 mL g^?1, 10.0 min for the temperature, the ratio of the volume of used Schiff base solution to the amount of oil, and the stirring time, respectively. Method validation was performed with recovery experiments in the analysis of the oil-based metal standard by flame atomic absorption spectrometry, limit of detection, and the relative standard deviation of the proposed method were found to be 0.09 μg g^?1 and 1.04 %, respectively. Additionally, an alternative determination procedure (inductively coupled plasma optical emission spectrometry) was applied for the comparison. This paper describes a simple, cheap, rapid, efficient, sensitive, and accurate alternative analytical method for the iron determination in oils. The proposed method was applied on six different oil samples and the iron concentration was found in the range of 0.38–0.70 μg g^?1.     

A Highly Sensitive Method for the Determination of Thiophanate Methyl,Cyromazine, and Their Metabolites in Edible Fungi by Ultra-Performance Liquid Chromatography Using Accelerated Solvent Extraction and Cleanup with Solid-Phase Extraction

A highly sensitive ultra-performance liquid chromatographic method with diode-array detection was developed for residue determination of thiophanate methyl (TM), cyromazine (CYR), and their metabolites, carbendazim (MBC) and melamine (MEL). Edible fungi samples were treated using accelerated solvent extraction (ASE) followed by cleanup with solid-phase extraction (SPE). Under optimized conditions, good linearity was achieved with a correlation coefficient (r ²) of ≥0.9998. The limit of quantification was 0.36, 0.24, 0.4, and 0.5 μg kg^?1 for MEL, CYR, MBC, and TM, respectively. The intra- and interday precisions (in terms of the relative standard deviation (RSD)) of the four analytes were in the range of 2.3–4.5 and 3.1–6.3 %, respectively. The recoveries for TM, MBC, CYR, and MEL in four edible fungi samples at three spiked levels of 0.6, 6, and 20 μg kg^?1 for TM and MBC and 0.4, 4, and 20 μg kg^?1 for CYR and MEL were in the range of 82–105 % with RSDs below 5.6 %. The proposed method can be used for the routine determination of CYR and MEL in edible fungi with high sensitivity and accuracy as well as low consumption of reagents.     

Evaluation of the Spoilage of Raw Chicken Breast Fillets Using Fourier Transform Infrared Spectroscopy in Tandem with Chemometrics

The aim of this work was to evaluate the potential of Fourier transform infrared (FTIR) spectroscopy as a rapid and accurate technique to detect and predict the onset of spoilage in fresh chicken breast fillets stored at 3, 8, and 30 °C. Chicken breasts were excised from carcasses at 6 h post-mortem; cut in fillets; packed in air; stored at 3, 8, and 30?ºC; and periodically examined for FTIR, pH, microbiological analysis, and sensory assessment of freshness. Partial least squares regression allowed estimations of total viable counts (TVC), lactic acid bacteria (LAB), Pseudomonas spp., Brochothrix thermosphacta, Enterobacteriaceae counts and pH, based on FTIR spectral data. Analysis of an external set of samples allowed the evaluation of the predictability of the method. The correlation coefficients (R²) for prediction were 0.798, 0.832, 0.789, 0.810, 0.857, and 0.880, and the room mean square error of prediction were 0.789, 0.658, 0.715, 0.701, 0.756 log cfu g^?1 and 0.479 for TVC, LAB, Pseudomonas spp., B. thermosphacta, Enterobacteriaceae, and pH, respectively. The spectroscopic variables that can be linked and used by the models to predict the spoilage/freshness of the samples, pH, and microbial counts were the absorbency values of 375 wave numbers from 1,700 to 950 cm^?1. A principal component analysis led to the conclusion that the wave numbers that ranges from 1,408 to 1,370 cm^?1 and from 1,320 to 1,305 cm^?1 are strongly connected to changes during spoilage. These wave numbers are linked to amides and amines and may be considered potential wave numbers associated with the biochemical changes during spoilage. Discriminant analysis of spectral data was successfully applied to support sensory data and to accurately bound samples freshness. According to the results presented, it is possible to conclude that FTIR spectroscopy can be used as a reliable, accurate, and fast method for real time freshness evaluation of chicken breast fillets during storage.     

Antimicrobial Polylactic Acid Packaging Films against Listeria and Salmonella in Culture Medium and on Ready-to-Eat Meat

The contamination of Listeria monocytogenes and Salmonella spp. in ready-to-eat (RTE) meat products has been a concern for the meat industry. In this study, edible chitosan-acid solutions incorporating lauric arginate ester (LAE), sodium lactate (NaL), and sorbic acid (SA) alone or in combinations were developed and coated on polylactic acid (PLA) packaging films. Antimicrobial effects of coated PLA films on the growth of Listeria innocua, L. monocytogenes, and Salmonella Typhimurium in a culture medium (tryptic soy broth, TSB) and on the surface of meat samples were investigated. Antimicrobial PLA films containing 1.94 mg/cm² of chitosan and 1.94 μg/cm² of LAE were the most effective against both Listeria and Salmonella in TSB and reduced them to undetectable level (<0.69 log CFU/ml). The same PLA films with LAE significantly (p?L. innocua, L. monocytogenes, and S. Typhimurium on RTE meat during 3 and 5 weeks’ storage at 10 °C, achieving 2–3 log reduction of Listeria and 1–1.5 log reduction of Salmonella as compared with controls. PLA films coated with 1.94 mg/cm² of chitosan, 0.78 mg/cm² of NaL, and 0.12 mg/cm² of SA significantly reduced the growth of L. innocua but were less effective against Salmonella. The combination of NaL (0.78 mg/cm²) and SA (0.12 mg/cm²) with LAE (1.94 μg/cm²) did not generate additional or synergetic antimicrobial effect against Listeria or Salmonella on the meat surface. L. innocua had a similar sensitivity to the film treatments as L. monocytogenes, suggesting that L. innocua may be used as a surrogate of L. monocytogenes for further scaleup and validation studies. The film treatments were more effective against the microorganisms in TSB culture medium than in RTE meat, which suggests that in vivo studies are a necessary step to develop antimicrobial packaging for applications in foods.     

FTIR Spectroscopy Combined with Chemometric for Analysis of Sesame Oil Adulterated with Corn Oil

Sesame oil is an edible vegetable oil derived from the sesame seed that has been used as a flavor enhancer in Southeast Asian cuisine. This highly valuable oil can be subjected to adulterations with lower price oils in order to gain economical profit. Among 10 vegetable oils evaluated using fatty acid profiles with principal component analysis, corn oil has the closest similarity in fatty acids combined together with sesame oil; therefore, corn oil is a potential adulterant in sesame oil. FTIR spectra at 1072?935 cm^?1 was chosen for quantitative analysis with acceptable values of coefficient determination (R²), root mean square errors of calibration and prediction. These combined methods using first derivative FTIR spectra in partial least square showed well quantified corn oil in sesame oil with R² (0.992), root mean square errors of calibration (0.53% v/v) and root mean square errors of prediction (1.31% v/v) values. Moreover, the Coomans plot based on Mahalanobis distance were able to discriminate between sesame oil with adulterated oils such as corn oil, grape seed oil, and rice bran oil.     

Survey of polycyclic aromatic hydrocarbons of vegetable oils and oilseeds by GC-MS in China

There is a lack of information regarding the occurrence and content of contamination of polycyclic aromatic hydrocarbon (PAH) in edible vegetable oils and oilseeds used for oil production in China. By combining the advantages of ultrasound-assisted extraction, low temperature separation and silica SPE purification, a method for the determination of the USEPA, 16 PAHs was developed based on GC-MS to fill this gap. The method recoveries for oils and oilseeds were 84.4–113.8% and 84.3–115.3%, respectively. The LODs and LOQs for 16 PAHs were ranged from 0.06–0.17 and 0.19–0.56 μg kg^–1, respectively. Based on the established method, PAH concentrations in 21 edible oils and 17 oilseeds were determined. Almost all the PAHs were found in all the samples tested, especially the light PAHs (LPAHs). Three oil samples exceeded the maximum level of 10 μg kg^–1 for BaP set by China. However, five and six oil samples, respectively, exceeded the maximum limits of 2 and 10 μg kg^–1 set for BaP and PAH4 by the European Union. The concentrations of PAH16 in oilseed samples were 1.5 times higher than corresponding oil samples. The relationships between PAH4 and PAH8, PAH4 and PAH16 as well as PAH8 and PAH16 indicates that PAH4 is a sufficient surrogate for the contamination level of PAHs in edible oils when compared with PAH8.     

Simultaneous Determination of TBH<Subscript>2</Subscript>Q and BHA Antioxidants in Food Samples Using Eosin Y Film Modified Electrode

A glassy carbon electrode (GCE) was modified with eosin Y that was electrodeposited on GCE via continuous cycling between ??1.6 and 1.5 V (vs Ag/AgCl). This electrode was characterized by scanning electron microscopy and electrochemical impedance spectra. The resulting electrode exhibited excellent electrocatalytic activity toward the oxidation of butylated hydroxyanisole (BHA) and tert-butyl hydroquinone (TBH₂Q); in addition, the oxidation products of BHA and TBH₂Q were found to be the same, which was studied by CV and in situ FT-IR spectroelectrochemistry. Under the optimized condition, the oxidation peak currents were linear to BHA/TBH₂Q in the range from 0.10 to 7.00 μg mL^?1 with the detection limits of 0.01 μg mL^?1 (S/N?=?3) for BHA and 0.015 μg mL^?1 (S/N?=?3) for TBH₂Q, respectively. Moreover, the reproducibility and repeatability of the electrode were determined. The proposed method was successfully applied in the simultaneous determination of BHA and TBH₂Q in several edible oil samples, and satisfactory results when compared with those obtained using high-performance liquid chromatography.     

Effects of Dielectric Barrier Discharges (DBD) Cold Plasma Treatment on Physicochemical and Structural Properties of Zein Powders

Zein powders were subjected to dielectric barrier discharges (DBD) cold plasma (CP) treatment, and the physicochemical and structural properties were investigated. The results indicated that CP treatment decreased the average diameter of zein micelles. It also increased the free sulfhydryl (SH) group concentration and decreased the pH of zein solutions. Significant improvement was observed in solubility of zein in both neutral and acidic water solutions after treatment. Differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS) results indicated the conformation rearrangement for all treated samples. FTIR spectrum confirmed the change of secondary structure for amide I region (1600–1700 cm^?1) after CP treatment. Furthermore, the film-forming properties of zein were also studied. It was found that the increase of CP treatment time could reinforce the tensile strength (TS) and surface hydrophilicity of zein films. It is suggested that the DBD CP treatment technology can improve the utilization and broaden the application field of zein as an effective modification method.