Cottonseed oil estimation by pulsed nuclear magnetic resonance technique

Seed asymmetry and moisture associated with the seeds are known to affect seed oil estimation by pulsed nuclear magnetic resonance (NMR) technique employing free induction decay or single spin echo (SE) pulse sequence. UsingGossypium (cottonseeds) as experimental material, it is shown that transverse relaxation times (T₂) of seed oil, in different varieties of seeds, measured in vivo, are not the same. The mean T₂ value of tetraploid seeds is found to be significantly higher than that of diploids. The effect of T₂ variation and other problems on oil estimation by the free induction decay and SE methods can be avoided by using the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence to monitor the signal intensities of a certain number of selected echoes and processing them to yield the extrapolated signal intensity at zero time. The oil content values thus estimated are found to agree well with those obtained by Soxhlet method. The agreement between the two methods might depend upon the presence of gossypol and other pigments present in the samples. Neither delinting nor dehydrating the seeds is necessary in the present method. Even with the CPMG sequence, use of individual echoes is not recommended, as the T₂ variations give rise to erroneous values.     

Rapid and nondestructive determination of seed oil by pulsed nuclear magnetic resonance technique

The pulsed NMR technique for rapid and nondestructive determination of oil in oilseeds has been developed. The effects of spin-lattice relaxation time, spin-spin relaxation time, seed moisture, angular position of the seeds, sample tube thickness, and sample height upon the magnitude and reproducibility of the NMR signal were studied. Based upon these studies, various parameters for seed oil analysis have been fixed. The oil content of Brassica, peanut, and sunflower seeds was determined. The reproducibility of the measurement is ± 1 %. The technique was tested by measuring the oil content of the same seeds by the cold percolation method (CCl₄ extraction). It was further tested by determining the oil content of 60 Brassica seed samples independently at three laboratories. The results of these tests are given.     

A comparison of different pulse sequences in the nondestructive estimation of seed oil by pulsed nuclear magnetic resonance technique

Three basic pulse sequences,viz., Free Induction Decay (FID), Spin Echo (SE) and Carr-Purcell-Meiboom-Gill (CPMG), available in the pulsed nuclear magnetic resonance technique have been used to estimate the relative oil content in single as well as bulk samples of oil-bearing seeds. Conclusive evidence has been presented to show that the CPMG sequence is vastly superior to the other two as far as the effects of seed orientation and moisture content are concerned.     

Simultaneous determination of moisture and oil content in oilseeds by pulsed nuclear magnetic resonance

Pulsed nuclear magnetic resonance technique using Carr-Purcell-Meiboom-Gill (CPMG) sequence has been used for simultaneous determination of moisture and oil content in rapeseed-mustard. This method involves sampling the free induction decay (FID) following 90° pulse in the CPMG sequence and resolving the trace of the amplitude of the CPMG echo signals into exponentially decaying liquid components of oilseeds. The data show that water in oilseeds generally exists in 2 phases and the relatively slow decaying component disappears around moisture content of 7% and below. The moisture and oil content have been determined by the method for 34 samples of 5 different varieties of seeds at varying moisture levels (∼3% to 22%). The measured moisture and oil content have been compared with the values obtained by the oven drying method and earlier known FID method of pulsed nuclear magnetic resonance (NMR) respectively, and the agreement is fairly good for rapid estimation with standard deviation of 0.70% for oil content and 0.99% for moisture content. This is a rapid and nondestructive method for determination of both moisture and oil content without weighing and drying the seeds and also seems suitable for other matrix samples.     

Seed oil determination by pulsed nuclear magnetic resonance without weighing and drying seeds

Pulsed nuclear magnetic resonance (NMR), which takes about 10 sec per analysis, has been used for rapid nondestructive determination of oil in oilseeds without weighing and oven drying the seeds. This has been done by measuring the free induction decay (FID) signal of solid and liquid in oilseeds. The oil values determined by this method for mustard, sunflower, and soybean seeds have been compared with the values determined by measuring the oil signal alone in the intact seeds, which takes about 2 min per analysis. Correlation for mustard is 0.988, for sunflower 0.945, and for soybean 0.931. The reasons for better agreement for mustard and the way of improving it for sunflower and soybean have been discussed.     

Determination of the solid fat content of commercial fats by pulsed nuclear magnetic resonance

A method and instrumentation for measuring the solid fat content is reported that is both accurate and precise. It involves using transient nuclear magnetic resonance (NMR) measurements for determining the percentage of solids in commercial shortenings and hydrogenated oils at selected temperatures. The incorporation of a tempering step at 26.7 C for all samples before measurement has improved the precision of the solids content actually measured (±0.2% solids) which approximates that of dilatometry. Duplicate measurements are not required to obtain this precision. The instrument is equipped with six 10-mm sample holders in combination with a precise variable temperature accessory system which eliminates the temperature difference between the sample and sample holder. This improved and exact temperature conditioning of samples provides better sample stability and easier handling for routine conditions of analysis. A single temperature result can be made in less than 1 hr and typical 5 temperature results obtained in 2.5 hr. Our work also indicates that tempering does influence results, the net effect being to decrease the amount of solids at temperatures less than the tempering temperature. In comparing the pulsed NMR measured solids with these measured by dilatometry, differences between methods of measurement are minimized when samples have had the same tempering and temperature history. This method provides flexibility, speed, and increased sample throughput of up to 60 samples/day. The self-contained equipment requires only 9 sq ft of space and is ready for measurements within 45 min after start-up.     

核磁共振法测定涤纶长丝含油率

采用核磁共振仪测试涤纶长丝含油率,初步探讨了其在生产过程中的应用。结果表明:与传统洗涤法相比,核磁共振法具有快速、简便、试样不需制备、不称重、不需溶剂的优点,且测试精密度和准确度高。     

Simultaneous determination of oil and water contents in different oilseeds by pulsed nuclear magnetic resonance

Routine analysis of oil and water contents in different oilseeds with the Bruker Minispec pulsed nuclear magnetic resonance (NMR) analyzer (Bruker Analytische Mestechnik, Rheinstetten, Germany) is rapid (16 s measurements), precise, accurate and nondestructive. In 1991, subcommittee SC2 (oil seeds) of the Technical Committee Number 34 [organized by the International Standards Organization (ISO), Geneva, Switzerland] organized an international collaborative study for pulsed NMR analysis of oil content in whole rapessed. An additional study was performed in 1993 to extend the method to sunflower, linseed and soy seeds. The Draft International Standard ISO DIS/10565 (Draft International Standards, International Standards Organization, Geneva, 1993) describes the procedure of the pulsed NMR method for determination of oil content in rapeseed and presents the interlaboratory comparison results based on the calculations described in the Normative ISO 5725 (Draft International Standards, International Standards Organization, Geneva, 1993). The standard was approved in 1992 and will be published in 1993. The interlaboratory collaborative studies showed that the analyses of oil and moisture by pulsed NMR were either comparable or more repeatable than measurements done by the traditional methods. No statistical differences between determinations by the traditional and pulsed NMR methods were found. Simultaneous determination of percent moisture and percent oil content in whole seeds is possible with pulsed NMR by the spin-echo method. In addition, multiple components of the oil can be detected and quantitated by T2 analysis from the Carr-Purcell-Meiboom-Gill pulse sequence. The instrument is easy to calibrate with whole oilseeds, and the calibration can be checked periodically with the same seeds because the measurement is nondestructive. Pulsed NMR provides a rapid alternative to the long, laborious, traditional methods of analysis and offers substantial long-term savings of both time and money. Minimal operator training is required once the technique has been established for routine use. Presented at the 84th AOCS Annual Meeting & Expo, April 27, 1993, Anaheim, California.     

High-throughput determination of oil content in corn kernels using nuclear magnetic resonance imaging

A new high-throughput method for measuring oil content in intact, single corn kernels is demonstrated using nuclear magnetic resonance imaging (MRI) methods. This nondestructive technique enables the evaluation of relative oil content in up to 2,592 corn kernels in less than 40 min using a 1.5 T clinical MRI scanner. Custom software was developed to process and analyze 3-D magnetic resonance (MR) image data rapidly. The precision and accuracy of the MR method for measuring oil content are discussed. The precision of the MRI results is shown to be dependent on MR scanner noise. The MRI results show very good relative accuracy compared with low-field NMR, NIR transmission, and accelerated solvent extraction measurements. Minor differences between the MRI and low-field NMR experimental protocols were shown to be inconsequential to the oil content measurement. Extending the MRI method to the analysis of other oilseeds and/or the use of other magnetic field strengths is discussed, as is a comparison of this MRI method relative to other high-throughput magnetic resonance screening techniques.     

Average molecular weight of oil fractions by nuclear magnetic resonance

Average molecular weight (AMW) is an important parameter of the ‘average molecule’ in oil fractions. Normally it is measured by vapour pressure osmometry (VPO), but it would be useful to have an alternative measurement. A simple algorithm based on data from the n.m.r. spectra for the calculation of a maximum AMW, considering molecules with fully extended aromatic nuclei (cata-condensed molecules), and of a minimum AMW, considering molecules with maximum condensation of the aromatic nuclei, is presented in this paper. The values obtained are consistent with VPO values for different fractions as distillates, residues or asphaltenes. This method completes the data for a full characterization of the average molecule using only n.m.r..     

Measurement of emulsion stability by pulsed nuclear magnetic resonance (NMR)

The stability of emulsions can be measured rapidly and accurately using pulsed nuclear magnetic resonance (NMR).     

Analysis of rich oil shales by 1H nuclear magnetic resonance

The potential yields of rich oil shales from the Colorado Green River Basin were measured by pulsed ¹H nuclear magnetic resonance. The rates of decay of the signals, as quantified by their second moments, decreased with increasing organic content. This implies that whenever shales of widely varying yields are being compared, their free-induction-decays must be extrapolated to time zero.     

Use of pulsed nuclear magnetic resonance to predict emulsion stability

Pulsed nuclear magnetic resonance (NMR) was used to measure extent of oil solidification during cooling of oil-in-water emulsions. “Percent interaction,” derived from these measurements, was found to correlate well with actual resistance of the emulsion to creaming and phase separation during storage. Average oil droplet size gave a fair correlation with stability, but the correlation of required Hydrophile-Lipophile Balance (HLB) with stability was poor. Pulsed NMR cooling curve measurements on emulsions offer an improved method for prediction of emulsion stability. Presented at the AOCS Meeting in Chicago, September 1976.     

The determination of the solids content of fats and oils by nuclear magnetic resonance

A nuclear magnetic resonance (NMR) method was developed for the determination of the solids content of fats and oils at various temperatures. This method is more rapid, accurate, and uni-versally applicable than the generally accepted solids fat index (SFI) by the dilatometric pro-cedure. A standard deviation of 1.0% solids, unaffected by parameter interactions and attain-able by inexperienced operators, indicates good reliability and reproducibility. The utilization of an NMR variable-tempera-ture accessory and a more precise mode of NMR tuning improves the precision and accuracy. The direct calculation of percentage of solids from the NMR signals eliminates the need for standards and compensates for the temperature variable. The results indicate that two separate labora-tories, using somewhat different methods and modes of NMR operation, agree reasonably well.     

Identification of chondrillasterol in twoCucurbitaceae seed oils by proton nuclear magnetic resonance spectroscopy

The absolute configuration at C-24 of C-24 epimeric 24-ethyl-5α-cholesta-7,E-22-dien-3β-ols I–IV previously isolated from tea seed oil, shea fat, and gourd and sponge cucumber seed oils, respectively, was studied by proton nuclear magnetic resonance spectroscopy. The results showed that the sterols I and II are identical with spinasterol (24S/α-ethyl group), whereas the sterols III and IV are identified as its 24R/β-epimer, chondrillasterol. This study has thus for the first time properly documented the presence in tracheophytes of a 24β-ethylsterol in which Δ²⁵⁽²⁷⁾-bond is reduced.     

Determination of oil,starch, and protein content of viable intact seeds by carbon-13 nuclear magnetic resonance

Dipolar-decoupled natural abundance¹³C NMR spectra of some intact seeds have been obtained at 22.6 MHz. The spectra display reasonalby well resolved resonance lines for rigid materials, such as the starch and protein components of the seeds, in addition to well resolved lines for the mobile oil component, and, hence, should be useful in rapid nondestructive analyses of total composition.     

13C nuclear magnetic resonance spectroscopic analysis of the triacylglycerol composition ofBiota orientalis and carrot seed oil

¹³C nuclear magnetic resonance (NMR) spectroscopic analysis of the whole oil (triacylglycerols) ofBiota orientalis seeds confirms the presence of oleate [18:1(9Z)], linoleate [18:2(9Z, 12Z)], linolenate [18:3((9Z, 12Z, 15Z)], 20:3 (5Z, 11Z, 14Z), 20:4(5Z, 11Z, 14Z, 17Z), and saturated fatty acids in the acyl groups by comparing the observed carbon shifts with previously established shift data for model triacylglycerols. This technique shows that the saturated, 20:3 and 20:4 fatty acids are distributed mainly in the α-acyl positions, whereas oleate, linoleate, and linolenate are randomly acylated to the α- and β-positions of the glycerol “backbone”. Stereospecific hydrolysis of theBiota oil with pancreatic lipase, followed by chromatographic analysis of fatty esters, reveals the presence of trace amounts of 16:0(0.7%), 18:0(0.5%), 20:3 (0.4%), and 20:4 (1.3%) in the β-position of the glycerol “backbone”, which are undetectable by¹³C NMR technique on the whole oil. Semiquantitative assessment of the¹³C NMR signal intensities gives the relative percentages of the fatty acid distribution as: saturated 16:0, 18:0 (12.0% α-acyl), oleate (7.7% α-acyl 8.7% β-acyl), total linoleate and linolenate (31.7% α-acyl; 24.2% βacyl), total 20:3 and 20:4 (15.7% α-acyl). The¹³C NMR spectroscopic analysis of carrot seed oil identifies the presence of saturated (18:0), 18:1(6Z), 18:1(9Z), and 18:2(9Z, 12Z). The saturated fatty acid is found in the α-acyl positions. Semi-quantitative assessment of the signal intensities gives the relative percentages of the fatty acids as: 18:0 (4.5% α-acyl), 18:1(6Z) (49.6% α-acyl; 19.7% β-acyl), oleate (6.5% α-acyl; 8.6% β-acyl) and linoleate (5.2% α-acyl; 6.9% β-acyl).     

Nuclear magnetic resonance for determining oil content of seeds

Twelve seed oils containing a variety of functional groups were examined with a commercial broad-band nuclear magnetic resonance (NMR) spectrometer. Instrument response (integrator readout) was directly related to hydrogen content of the oil (r=0.999), regardless of the structures present. NMR techniques were applied to the determination of oil in intact, partially dried seeds from 18 plant species containing 1.5–53% oil having a variety of structures. The correlation between integrator readout (calculated to a uniform 25-g sample weight) and oil content (determined by extraction with petroleum ether) is excellent (r=0.993). If the readout is further modified by a correction for the variation in hydrogen content of the oils, the correlation becomes 0.996.     

Estimation of solid-liquid ratios in bulk fats and emulsions by pulsed nuclear magnetic resonance

Several pulsed nuclear magnetic resonance (NMR) methods were evaluated to estimate the solid fat content of fats and oil-in-water emulsions. The methods were checked with samples of paraffin oil or triolein containing known quantities of crystalline tristearate. A method based on the signal of solid fat (with use of a correction factor, the “f-factor”) was rejected in this work for general use. Correct results were obtained with methods that used only the signal of the liquid phase. With emulsions, disturbances could arise due to the surfactant present and to possible solubilization of water in the oil phase, presumably by monoglycerides. Without these disturbances, solid fat content in emulsions could be estimated as in bulk fats, after correction of the liquid phase signal for the contribution of protons from the aqueous phase. The signal from fat crystals inside emulsion droplets differed from that of crystals of the same fat in bulk, which may have been due to difference in crystal size but not to difference in crystal modification. Measurements on natural cream showed that disturbances were also possible in this type of emulsion.     

Fat content and liquid-to-solid ratio of chocolate by wide line nuclear magnetic resonance

Wide line nuclear magnetic resonance (NMR) was used for fast and accurate determination of the fat content and liquid-to-solid ratio of chocolate. The transition range of solid to liquid was found to be extremely narrow. The temp effect on the NMR signal is discussed and correction methods are suggested to that effect. A method was developed for the separate determination of butter fat and cocoa fat in addition to the total fat content determination in milk chocolate.