A Primary Method for the Determination of Hydroxyl Value of Polyols by Fourier Transform Mid-Infrared Spectroscopy

A primary Fourier transform infrared (FTIR) method was developed to determine the hydroxyl value (OHV) of polyols produced from edible oils. The method is a modification of American Society for Testing and Materials 1899‐08, using toluene as the solvent to dissolve the sample and to carry the reactive reagent p‐toluenesulfonyl isocyanate (TSI). TSI reacts with OH groups to produce a carbamate, a functional group that can be measured spectrally between ~1780 and 1690 cm^?1 in the differential spectrum that is obtained from spectra collected before and after the reaction. Commercially available 1‐nonanol, which has a defined OHV, is used to develop a calibration. The OHV for a variety of 1° and 2° alcohols, as well as petrochemical and lipid‐based polyols, were then measured to evaluate the performance of the method and to assess the effects of moisture on the results. The FTIR OHV were in accord with the results obtained by AOCS method Cd 13‐60 and were demonstrated to be unaffected by the presence of moisture in the sample. The new TSI‐FTIR method is simpler, much faster (~10 min), and more reproducible and accurate than the AOCS OHV titrimetric methods and is not affected by carboxylic acids, amines or moisture.     

A new method for determining gossypol in cottonseed oil by FTIR spectroscopy

A new method was developed to determine the gossypol content in cottonseed oil using FTIR spectroscopy with a NaCl transmission cell. The wavelengths used were selected by spiking clean cottonseed oil to gossypol concentrations of 0–5% and noting the regions of maximal absorbance. Transmittance values from the wavelength regions 3600–2520 and 1900–800 cm⁻¹ and a partial least squares (PLS) method were used to derive FTIR spectroscopic calibration models for crude cottonseed, semirefined cottonseed, and gossypol-spiked cottonseed oils. The coefficients of determination (R ²) for the models were computed by comparing the results from the FTIR spectroscopy against those obtained by AOCS method Ba 8-78. The R ² were 0.9511, 0.9116, and 0.9363 for crude cottonseed, semirefined cottonseed, and gossypol-spiked cottonseed oils, respectively. The SE of calibration were 0.042, 0.009, and 0.060, respectively. The calibration models were cross-validated within the same set of oil samples. The SD of the difference for repeatability and accuracy of the FTIR method were better than those for the chemical method. With its speed (ca. 2 min) and ease of data manipulation, FTIR spectroscopy is a useful alternative to standard wet chemical methods for rapid and routine determination of gossypol in process and/or quality control for cottonseed oil.     

Rapid Method for the Determination of Moisture Content in Biodiesel Using FTIR Spectroscopy

A new, rapid, and direct method was developed for the determination of moisture content in biodiesel produced from various types of oils using Fourier transform infrared (FTIR) spectroscopy with an attenuated total reflectance (ATR) element. Samples of biodiesels used in this study were produced using sludge palm oil (SPO). The calibration set was prepared by spiking double-distilled water into dried biodiesel samples in ratios (w/w) between 0 and 10% moisture. Absorbance values from the wavelength regions 3,700–3,075 and 1,700–1,500 cm⁻¹, and the partial least square (PLS) regression method were used to derive a FTIR spectroscopic calibration model for moisture content in biodiesel samples. The coefficient of determinations (R ²) for the models was computed by comparing the results obtained from FTIR spectroscopy against the values of the moisture concentrations (%) determined using the American Oil Chemists’ Society (AOCS) oven method Ca 2d-25. Same comparison was done using International Union of Pure and Applied Chemistry (IUPAC) distillation method 2.602. R ² was 0.9793 and 0.9700 using AOCS and IUPAC methods, respectively. The standard error (SE) of calibration was 1.84. The calibration model was cross validated within the same set of samples, and the standard deviation (SD) of the difference for repeatability (SDDr) and accuracy (SDDa) of the FTIR method was determined. With its speed and ease of data manipulation, FTIR spectroscopy is a useful alternative method to other methods for rapid and routine determination of moisture content in biodiesel for quality control.     

Industrial validation of fourier transform infrared trans and lodine value analyses of fats and oils

A Fourier transform infrared (FTIR) edible oil analysis package designed to simultaneously analyze for trans content, cis content, iodine value (IV), and saponification number (SN) of neat fats and oils by using calibrations based on pure triglycerides and derived by application of partial-least-squares (PLS) regression was assessed and validated. More than 100 hydrogenated rapeseed and soybean samples were analyzed by using the edible oil analysis package as well as the newly proposed modification of the AOCS IR trans method with trielaidin in a trans-free oil as a basis for calibration. In addition, ∼1/3 of the samples were subsequently reanalyzed by gas chromatography (GC) for IV and trans content. The PLS approach predicted somewhat higher trans values than the modified AOCS IR method, which was traced to a combination of the inclusion of trilinolelaidin in the calibration set and the effects of baseline fluctuations. Eliminating trilinolelaidin from the triglyceride standards and the use of second-derivative spectra to remove baseline fluctuations produced excellent concurrence between the PLS and modified AOCS IR methods (mean difference of 0.61% trans). Excellent internal consistency was obtained between the IV and cis and trans data provided by the edible oil analysis package, and the relationship was close to that theoretically expected [IV=0.86 (cis + trans)]. The IV data calculated for the GC-analyzed samples matched the PLS IV predictions within 1 IV unit. The trans results obtained by both IR methods were linearly related to the GC data; however, as is commonly observed, the GC values were significantly lower than the IR values, the GC and IR data being related by a slope factor of ∼0.88, with an SD of ∼0.80. The concurrence between the trans data obtained by the two FTIR methods, and between the FTIR and GC-IV data, as well as the internal consistency of the IV, cis and trans FTIR predictions, provides strong experimental evidence that the edible oil analytical package measures all three variables accurately. Co-Director, McGill IR Group.     

Stoichiometric determination of hydroperoxides in fats and oils by fourier transform infrared spectroscopy

A primary Fourier transform infrared (FTIR) spectroscopic method for the determination of peroxide value (PV) in edible oils was developed based on the stoichiometric reaction of triphenylphosphine (TPP) with hydroperoxides to produce triphenylphosphine oxide (TPPO). Accurate quantitation of the TPPO formed in this reaction by measurement of its intense absorption band at 542 cm⁻¹ provides a simple means of determining PV. A calibration was developed with TPPO as the standard; its concentration, expressed in terms of PV, covered a range of 0–15 PV. The resulting calibration was linear over the analytical range and had a standard deviation of ±0.05 PV. A standardized analytical protocol was developed, consisting of adding ∼0.2 g of a 33% (w/w) stock solution of TPP in hexanol to ∼30 g of melted fat or oil, shaking the sample, and scanning it in a 100-μm KCI IR transmission cell maintained at 80°C. The FTIR spectrometer was programmed in Visual Basic to automate scanning and quantitation, with the reaction/FTIR analysis taking about 2 min per sample. The method was validated by comparing the analytical results of the AOCS PV method to those of the automated FTIR procedure by using both oxidized oils and oils spiked with tert-butyl hydroperoxide. The two methods correlated well. The reproducibility of the FTIR method was superior (±0.18) to that of the standard chemical method (±0.89 PV). The FTIR method is a significant improvement over the standard AOCS method in terms of analytical time and effort and avoids solvent and reagent disposal problems. Based on its simple stoichiometry, rapid and complete reaction, and the singular band that characterizes the end product, the TPP/TPPO reaction coupled with a programmable FTIR spectrometer provides a rapid and efficient means of determining PV that is especially suited for routine quality control applications in the fats and oils industry.     

The determination of peroxide value by fourier transform infrared spectroscopy

A rapid method for the quantitative determination of peroxide value (PV) of vegetable oils by Fourier transform infrared (FTIR) transmission spectroscopy is described. Calibration standards were prepared by the addition oft-butyl hydroperoxide to a series of vegetable oils, along with random amounts of oleic acid and water. Additional standards were derived through the addition of mono- and diglyceride spectral contributions, as well as zero PV spectra obtained from deuterated oils. A partial least squares (PLS) calibration model for the prediction of PV was developed based on the spectral range 3750–3150 cm⁻¹. Validation of the method was carried out by comparing the PV of a series of vegetable oils predicted by the PLS model to the values obtained by the American Oil Chemists Society iodometric method. The reproducibility of the FTIR method [coefficient of variation (CV)=5%)] was found to be better than that of the chemical method (CV =9%), although its accuracy was limited by the reproducibility of the chemical method. The method, as structured, makes use of a 1-mm CaF₂ flow cell to allow rapid sample handling by aspiration. The spectrometer was preprogrammed in Visual Basic to guide the operator in performing the analysis so that no knowledge of FTIR spectroscopy is required to implement the method. The method would be suitable for PV determinations in the edible oil industry and takes an average of three minutes per sample.     

New FTIR method for the determination of FFA in oils

A rapid, practical, and accurate FTIR method for the determination of FFA in edible oils was developed. Analogous to the AOCS titration procedure, the FTIR FFA determination is effected by an acid/base reaction but directly measures the product formed rather than utilizing an end point based on an electrode potential or color change. A suspension of a weak base, potassium phthalimide (K-phthal) in 1-propanol (1-PrOH), is used to convert the FFA present in oils to their carboxylate salt without causing oil saponification, and differential spectroscopy is used to circumvent matrix effects. Samples are first diluted with 1-PrOH, then split, with one-half treated with the K-phthal reagent and the other half with 1-PrOH (blank reagent), their spectra collected, and differential spectra obtained to ratio out the invariant spectral contributions from the oil sample. Quantification of the percentage of FFA in the oil, expressed as %oleic acid, based on measurement of the peak height of the ν (COO⁻) absorption of the FFA salt formed, yielded a calibration with an SE of <0.020% FFA over the range of 0–4%. The method was validated by standard addition and the analysis of Smalley check samples, the results indicating that the analytical performance of the FTIR procedure is as good as or better than that of the standard titrimetric procedure. As structured, the FTIR procedure is a primary method, as calibration is not dependent on reference values provided by another method, and has performance criteria that could lead to its consideration as an instrumental AOCS procedure for FFA determination. The FTIR portion of the analysis is automatable, and a system capable of analyzing ∼60 samples/h was developed that could be of benefit to laboratories that carry out a large number of FFA analyses per day.     

Application of FTIR Spectroscopy for the Determination of Virgin Coconut Oil in Binary Mixtures with Olive Oil and Palm Oil

Rapid Fourier transform infrared (FTIR) spectroscopy combined with attenuated total reflectance (ATR) was applied for quantitative analysis of virgin coconut oil (VCO) in binary mixtures with olive oil (OO) and palm oil (PO). The spectral bands correlated with VCO, OO, PO; blends of VCO and OO; VCO and PO were scanned, interpreted, and identified. Two multivariate calibration methods, partial least square (PLS) and principal component regression (PCR), were used to construct the calibration models that correlate between actual and FTIR-predicted values of VCO contents in the mixtures at the FTIR spectral frequencies of 1,120–1,105 and 965–960 cm⁻¹. The calibration models obtained were cross validated using the “leave one out” method. PLS at these frequencies showed the best calibration model, in terms of the highest coefficient of determination (R ²) and the lowest of root mean standard error of calibration (RMSEC) with R ² = 0.9992 and RMSEC = 0.756, respectively, for VCO in mixture with OO. Meanwhile, the R ² and RMSEC values obtained for VCO in mixture with PO were 0.9996 and 0.494, respectively. In general, FTIR spectroscopy serves as a suitable technique for determination of VCO in mixture with the other oils.     

Comparison of four analytical methods for the determination of peroxide value in oxidized soybean oils

Previous work in our laboratory demonstrated that soybean oil oxidation, expressed as PV, can be determined using NIR transmission spectroscopy as an alternative to the official AOCS iodometric titration method. In the present study, a comparison of four peroxide analytical methods was conducted using oxidized soybean oil. The methods included the official AOCS iodometric titration, the newly developed NIR method, the PeroxySafe^™ kit, and a ferrous xylenol orange (FOX) method, the latter two being colorimetric methods based on oxidation of iron. Five different commercially available soybean oils were exposed to fluorescent light to obtain PV levels of 0–20 meq/kg; periodic sampling was done to ensure having representative samples throughout the designated range. A total of 46 oil samples were analyzed. Statistical analysis of the data showed that the correlation coefficient (r) and standard deviation of differences (SDD) between the standard titration and NIR methods were r=0.991, SDD=0.72 meq/kg; between titration and the PeroxySafe^™ kit were r=0.993, SDD=0.56 meq/kg; and between the standard titration and FOX method were r=0.975, SDD=2.3 meq/kg. The high correlations between the titration, NIR, and PeroxySafe^™ kit data indicated that these methods were equivalent.     

Simultaneous determination of lodine value and trans content of fats and oils by single-bounce horizontal attenuated total reflectance fourier transform infrared spectroscopy

A method for the simultaneous determination of iodine value (IV) and trans content from the Fourier transform infrared (FTIR) spectra of neat fats and oils recorded with the use of a heated single-bounce horizontal attenuated total reflectance (SB-HATR) sampling accessory was developed. Partial least squares (PLS) regression was employed for the development of the calibration models, and a set of nine pure triacylglycerols served as the calibration standards. Regression of the FTIR/PLS-predicted IV and trans contents for ten partially hydrogenated oil samples against reference values obtained by gas chromatography yielded slopes close to unity and SD of <1. Good agreement (SD<0.35) also was obtained between the trans predictions from the PLS calibration model and trans determinations performed by the recently adopted AOCS FTIR/SBHART method for the determination of isolated trans isomers in fats and oils.     

Determination of hexane residues in vegetable oils with FTIR spectroscopy

The FTIR spectroscopy method was developed for the determination of hexane residues in palm and groundnut (peanut) oils. The method was based on horizontal attenuated total reflectance with a ZnSe crystal at 45° at room temperature, and partial least squares (PLS) statistics were used to derive calibration models. The accuracy of the method was comparable to that of the AOCS Method Ca 3b-87, with coefficients of determination (R ²) of 0.9866 and 0.9810 for palm and groundnut oils, respectively, and SE of calibration of 3.83 and 4.91, respectively. The calibration models were validated, and the R ² of validation and the SE of prediction computed. The SD of the difference for repeatability for the method was comparable to that for the standard AOCS method when used for palm and groundnut oils. With its speed and ease of data manipulation by computer software, FTIR spectroscopy has an advantage over present chemical methods, which require preparation of the oil using toxic solvents before GC.     

Determination of iodine value with a fourier transform-near infrared based global calibration using disposable vials: An international collaborative study

A method for the determination of iodine value (IV) by Fourier transform-near infrared (FT-NIR) spectroscopy was developed and evaluated in an international collaborative study. The FT-NIR analyzer employed in this work uses disposable vials for sample handling and incorporates validation protocols designed to ensure that the calibration will give accurate results from analyzer to analyzer and stability over time without any further calibration development work. The global IV calibration was developed from over 1,200 animal, marine, and vegetable oils and fats, which were obtained on a number of different instruments worldwide. The Standard Error of Cross Validation measured from a range of 0–190 IV varied from ±0.2–1.4 IV (1 sigma). The repeatability for all models was on the order of 0.1 IV, which states that most of the error was inherited from the primary methods. Finally, an international interlaboratory study was carried out with 16 samples obtained from the AOCS Smalley Laboratory Proficiency Program and an oil processor. The average reproducibility error in any one lab was better than 0.15, and the average reproducibility between labs was better than 0.33. An uncertainty of 0.45 was calculated from the average FT-NIR values obtained from the collaborative study vs. the AOCS Certified Wijs method (Cd 1d-92).     

Upgrading the AOCS infrared trans method for analysis of neat fats and oils by fourier transform infrared spectroscopy

An automated protocol for the direct, rapid determination of isolated trans content of neat fats and oils by Fourier transform infrared (FTIR) spectroscopy was devised, based on a simple modification of the standard AOCS trans method, eliminating the use of CS₂ and methylation of low trans samples. Through the use of a commercially available, heated transmission flow cell, designed specifically for the analysis of neat fats and oils, a calibration (0–50%) was devised with trielaidin spiked into a certified, trans-free soybean oil. The single-beam spectra of the calibration standards were ratioed against the single-beam spectrum of the base oil, eliminating the spectral interference caused by underlying triglyceride absorptions, facilitating direct peak height measurements as per the AOCS IR trans method. The spectrometer was preprogrammed in Visual Basic to carry out all spectral manipulations, measurements, and calculations to produce trans results directly as well as to provide the operator with a simple interface to work from. The derived calibration was incorporated into the software package, obviating the need for further calibration because the program includes an automatic recalibration/standardization routine that automatically compensates for differences in optical characteristics between instruments, instrument drift over time, and cell wear. The modified AOCS FTIR analytical package was evaluated with Smalley check samples for repeatability, reproducibility, and accuracy, producing SD of ± 0.07, 0.13, and 0.70 trans, respectively, the FTIR predictions being linearly related to the Smalley means (r=0.999; SD=± 0.46), and well within one SD of the Smalley sample means. Calibration transfer was assessed by implementing the calibration on a second instrument and reanalyzing the Smalley check samples in cells of two different pathlengths (25- and 50-μm). There were no statistically significant differences between the FTIR trans predictions obtained for the Smalley samples from the two instruments and two cells, indicating that the software was able to adjust the calibrations to compensate for differences in instrument response and cell pathlength. The FTIR isolated trans analysis protocol developed by the McGill IR Group has the benefit of being based on the principles of an AOCS-approved method, matches its accuracy, and allows the analysis to be performed on both neat fats and oils, producing trans predictions in less than 2 min per sample. It is suggested that this integrated approach to trans analysis, which requires a minimum level of sample manipulation and operator skill, be considered as a modification of the proposed Recommended Practice CD14b-95.     

Determination of selenium,arsenic, iodine and bromine in fish,plant and mammalian oils by cyclic instrumental neutron activation analysis

The concentrations of arsenic, selenium, iodine and bromine in a series of fish, plant and mammalian oils have been determined by cyclic instrumental neutron activation analysis (CINAA). Crude fish oils contain between 0.047 and 0.151 μg Se g⁻¹, 2.36–14.5 μg As g⁻¹, 2.36–9.63 μg Br g⁻¹ and 0.97–4.76 μgI g⁻¹. Seal oil contains the same four elements, but at levels below the lower end of the fish oil ranges. Iodine, bromine and arsenic were not detected in rape-seed or soybean oils and the concentration of selenium varied from < 0.010 to 0.042 μg g⁻¹. The levels of selenium, iodine and bromine are reduced markedly by hydrogenation of the menhaden oils. The CINAA method yielded results which were in agreement with pub-lished values obtained by other methods. The technique was rapid, requiring minimal sample manipulation, and was essentially free from interferences.     

Oxidative stability of fat substitutes and vegetable oils by the oxidative stability index method

Oxidative Stability Index (OSI) of carbohydrate fatty acid polyesters, fat substitutes and vegetable oils were measured with the Omnion Oxidative Stability Instrument according to the new AOCS Standard Method Cd 12 B-92 (The Official Methods and Recommended Practices of the American Oil Chemists' Society, edited by D. Firestone, AOCS, Champaign, 1991). The stability of crude and refined, bleached and deodorized (RBD) vegetable oils (soybean, hydrogenated soybean and peanut) were determined at 110°C. In addition, OSI times for sucrose polyesters of soybean oil, butterfat, oleate:stearate and methyl glucoside polyester of soybean oil were determined in the absence and in the presence of 0.02 wt% antioxidants, [Tenox TBHQ (tertiary butylhydroquinone, Tenox GT-2 (from Eastman Chemical Products (Kingsport, TN); and vitamin E (from BASF, Wyandotte, MI)], and the results were compared with those of vegetable oils. Crude oils were most stable (20.4–25.9 h), followed by RBD oils (9.3–10.4 h) for soybean and peanut oils, respectively, and fat substitutes (3.8–6.8 h). Overall, Tenox TBHQ was the best antioxidant for improving the oxidative stability of both vegetable oils and fat substitutes. The sucrose polyester made with oleic and stearic acid was more stable than fat substitutes containing more polyunsaturated fatty acids, such as those from soybean oil, or from short-chain fatty acids, such as from butterfat. Antioxidants enhanced the stability of RBD oils (222% increase) and synthetic fat substitutes (421–424% increase) more than that of crude oils (33% increase). The shapes of the induction curves, not the actual OSI times for fat substitutes and vegetable oils, were similar and sharply defined.     

Determination of solid fat index by fourier transform infrared spectroscopy

A unique and rapid Fourier transform infrared (FTIR) spectroscopic method for the determination of solid fat index (SFI) of fats and oils was developed, which is capable of predicting the SFI profile of a sample in approximately two minutes, without the need for tempering. Hydrogenated soybean oil samples (n=72), pre-analyzed for SFI by dilatometry, were melted and their FTIR spectra acquired using a 25 μm NaCl transmission flow cell maintained at 80°C. Approximately half the samples were used for calibration, with the balance used as validation samples. Partial least squares (PLS) calibrations were developed from selected spectral regions that are associated with thecis, trans, ester linkage and fingerprint regions of the spectrum and related to the dilatometric SFI values obtained at 50, 70, 80, and 92°F. The calibrations were initially optimized and cross-validated by using the “leave one out” approach, with the accuracy and reproducibility of the calibration models assessed by predicting the validation samples. The overall cross validation accuracy of the PLS calibration models was in the order of ±0.71 SFI units over the four temperatures. Week-to-week validation accuracy and reproducibility was determined to be ±0.60 and ±0.38 SFI units, respectively, the reproducibility being within the specifications associated with the dilatometric reference method. To facilitate routine “on-line” FTIR analyses, a Visual Basic program was written to drive the spectrometer, prompt the user to load the sample, calculate, and print the SFI values determined from the PLS calibrations. As structured, the FTIR method has the potential to serve as a viable substitute for the traditional dilatometric SFI method, with the elimination of the tempering step reducing analysis time from hours to minutes. The FTIR approach should also be applicable to the determination of solid fat content if calibrated against solids data obtained by nuclear magnetic resonance.     

A modified method for determining free fatty acids from small soybean oil sample sizes

A modification of the AOCS Official Method Ca 5a-40 for determination of free fatty acids (FFA) in 0.3 to 6.0-g samples of refined and crude soybean oil is described. The modified method uses only about 10% of the weight of oil sample, alcohol volume, and alkali strength recommended in the Official Method. Standard solutions of refined and crude soybean oil with FFA concentrations between 0.01 and 75% were prepared by adding known weights of oleic acid. The FFA concentrations, determined from small sample sizes with the modified method, were compared with FFA percentages determined from larger sample sizes with the Official Method. Relationships among determinations obtained by the modified and official methods, for both refined and crude oils, were described by linear functions. The relationship for refined soybean oil had an R ² value of 0.997 and a slope of 0.99±0.031. The values for crude soybean oil are defined by a line with R ²=0.9996 and a slope of 1.01±0.013.     

Degumming and bleaching ofLesquerella fendleri seed oil

A lesquerella species (Lesquerella fendleri) being investigated as a domestic source of seed oil containing hydroxy fatty acids shows good agronomic properties and is being tested in semi-commercial production.Lesquerella fendleri seeds contain 25% oil, of which 55% is lesquerolic acid (14-hydroxy-cis-11-eicosenoic). Oils produced in pilot-plant quantities by screw press, prepress-solvent extraction and extrusion-solvent extraction processes have been refined in the laboratory by filtering, degumming and bleaching. Two American Oil Chemists’ Society (AOCS) standard bleaching earths and two commercial earths were compared for effectiveness in bleaching these dark, yellow-red, crude lesquerella oils. Free fatty acids (1.3%), iodine value (111), peroxide value (<4 meq/kg), unsaponifiables (1.7%) and hydroxyl value (100) were not significantly affected by degumming and bleaching, but phosphorus levels of 8–85 ppm in the crude oils were reduced to 0.5–1.1 ppm in the degummed and bleached oils. Crude oils had Gardner colors of 14, which were reduced to Gardner 9–11 in the degummed and bleached oil, depending on bleach type and quantity used. AOCS colors in the range of 21–25R 68–71Y were obtained. By including charcoal in the bleaching step, a considerably lighter oil could be obtained (Gardner 7).     

Di-Hydroxylated Soybean Oil Polyols with Varied Hydroxyl Values and Their Influence on UV-Curable Pressure-Sensitive Adhesives

Di-hydroxylated soybean oil (DSO) polyols with three different hydroxyl values (OHV) of 160, 240, and 285 mg KOH/g were synthesized from epoxidized soybean oils (ESO) by oxirane cleavage with water catalyzed by perchloric acid. The DSO were clear, viscous liquids at room temperature. The structure and physical properties of DSO were characterized using titration methods, Fourier-transform infrared spectroscopy (FTIR), gel permeation chromatography, rheometer, differential scanning calorimetry, and thermogravimetric analysis. The number average molecular weight of DSO160, DSO240, and DSO285 were 1,412, 1,781, and 1,899 g/mol, respectively, indicating that oligomerization occurred during DSO synthesis, which was further confirmed by FTIR. All DSO polyols exhibited non-Newtonian, shear thinning behavior. DSO with higher OHV were more viscous than those with lower OHV. All DSO were thermally stable up to 380 °C. These three DSO were formulated into pressure-sensitive adhesives (PSA) by copolymerizing with ESO using UV curing. The peel adhesion strength of the PSA was significantly affected by the OHV of DSO and DSO content. Maximal PSA adhesion strength of 4.6 N/inch was obtained with DSO285 and a DSO/ESO weight ratio of 0.75.     

Measurement of soybean fatty acids by near-infrared spectroscopy: Linear and nonlinear calibration methods

A key element of successful development of new soybean cultivars is availability of inexpensive and rapid methods for measurement of FA in seeds. Published research demonstrated applicability of NIR spectroscopy for FA profiling in oilseeds. The objectives of this study were to investigate the applicability of NIR spectroscopy for measurement of FA in whole soybeans and compare performance of calibration methods. Equations were developed using partial least squares (PLS), artificial neural networks (ANN), and support vector machines (SVM) regression methods. Validation results demonstrated that (i) equations for total saturates had the highest predictive ability (r ²=0.91–0.94) and were usable for quality assurance applications, (ii) palmitic acid models (r ²=0.80–0.84) were usable for certain research applications, and (iii) equations for stearic (r ²=0.49–0.68), oleic (r ²=0.76–0.81), linoleic (r ²=0.73–0.76), and linolenic (r ²=0.67–0.74) acids could be used for sample screening. The SVM models produced significantly more accurate predictions than those developed with PLS. ANN calibrations were not different from the other two methods. Reduction in the number of calibration samples reduced predictive ability of all equations. The rate of performance degradation of SVM models with sample reduction was the lowest.