Heat pretreatment of oilseeds: effect on oil quality

We studied the effect of seed conditioning via a rapid preheating technique to destroy the activity of oil-degrading enzymes. Rape and sunflower seeds were heated via steaming, oven cooking, infrared, and microwave. After the pretreatment the oil was expelled from the seeds by a screw press and its quality was determined via the analysis of oxidative stability, peroxide value, free fatty acid content, phosphorus, and iron. From the results it was concluded that preheating of the seeds leads to the expected decreased activity of lipase, but nevertheless increased levels of phosphorus and free fatty acids were observed. However, increased levels of phenolic antioxidants markedly improved the oxidative stability of rapeseed oil. From the techniques studied for heating of the seeds, microwave and steaming appeared to be the most suitable techniques. Both methods gave markedly improved oxidative stability, whereas steaming seemed to result in less formation of free fatty acids than microwave heating. Infrared heating led to rapidly burnt seeds and off-flavours.     

Practical nuclear magnetic resonance analysis of liquid oil in oilseeds: I factors affecting peak width

If proton nuclear magnetic resonance (NMR) spectra of single seeds can be improved, a rapid, low-cost method of screening seeds for oil composition could be developed for use as a selection tool in plant breeding. NMR spectroscopy was performed on single seeds of borage, flax, and canola to evaluate methods for improving spectra quality (narrowing peak widths and increasing signal-to-noise ratio) to a degree necessary to measure differences among seeds in a breeding program. Immersion of seeds in a variety of solvents, including deuterated chloroform, deuterated acetone, deuterated dimethyl sulfoxide (DMSO) and completely fluorinated hydrocarbons (FC-77), narrowed peaks obtained from seeds when compared with spectra from seeds analyzed in the absence of a solvent. Deuterated chloroform and FC-77 were free of interfering solvent proton peaks while deuterated acetone and deuterated DMSO contributed interfering peaks. The spectra of dehulled seeds had narrower peak widths than did seeds with hulls. Treatments that decreased seed oil viscosity failed to substantially narrow spectra peak widths of seeds. High magnetic field strength did not improve the spectral quality of seeds, as peak widths increased with field strength. Conversely, low field strength limited resolution of oil spectra. Although the 300 MHz spectrum of vegetable oil had greater resolution (narrower peaks) than the 60 MHz spectrum, spectra of seeds produced at 60 MHz had superior resolution to 300 MHz spectra.     

Determination of oil content in oilseeds by analytical supercritical fluid extraction

The total oil content of soyflakes, canola seed and wetmilled corn germ were determined by analytical supercritical fluid extraction (SFE) with carbon dioxide as the extraction solvent. Results obtained by SFE were in excellent agreement with those obtained by a conventional Soxhlet technique with organic solvents. The analytical-scale SFE technique yielded average means within one standard deviation of the means derived from the organic solvent-based methodology. Matrices containing both high and low oil content were successfully extracted with carbon dioxide at comparable precision to that obtained with the standard procedure. The supercritical fluid-based technique appears to be a suitable replacement for traditional extraction methods with organic solvents, thereby potentially eliminating the costs associated with solvent disposal and exposure of laboratory personnel to toxic and flammable solvents. Presented at the 4th International Symposium on Supercritical Fluid Chromatography and Extraction, Cincinnati, Ohio, May 20–22, 1992.     

Carbon-13 nuclear magnetic resonance analysis of intact oilseeds

High resolution natural abundance¹³C nuclear magnetic resonance (NMR) spectra of intact oilseeds have been obtained by Fourier transform techniques. The spectra can be interpreted in terms of the relative concentrations of the major fatty acids in the oilseed. The¹³C NMR spectra are well resolved despite the fact that¹H NMR spectra of the same seeds are poorly resolved. The difference in resolution can be attributed to the simplicity of the¹³C NMR spectra in which all spin-spin coupling can be removed, in which the separation of lines is increased by a factor of 30, and in which line broadening due to intermolecular dipolar interactions is not important. The¹³C NMR Fourier transform technique is sufficiently sensitive that a high quality spectrum can be obtained from a single soybean, for example, in about 10 minutes. Similar spectra of single seeds can be obtained in comparable times for corn, castor bean, peanut, sunflower seed, and rapeseed. Because the NMR technique is nondestructive, it can be used to select individual oilseeds for use in breeding programs designed to improve oil quality. By employing some special experimental NMR line narrowing techniques, it also appears feasible to obtain moderately well resolved, natural abundance¹³C NMR spectra of the immobile, rigid protein, and carbohydrate components of an intact oilseed, as well as the more mobile oil components.     

Further studies on a multisequential method for determination of oil content in oilseeds

The multisequential method for determination of oil content in oil seed developed at Svalöf has been used for ten years with good results. The mean values obtained in analysis of comparative samples of rape, turnip rape and white mustard for seven years in five countries with official methods agree well with the mean values from the multi-sequential method as used in four laboratories in Sweden. However, the variation coefficient is considerably smaller for the multisequential method. In addition to rape, turnip rape and white mustard, flaxseed, poppy seed, sunflower seed, safflower seed, soybeans and groundnuts can be successfully disintegrated in the steel tubes used in the multisequential method. The free fatty acid content of a rapeseed sample can be determined on the oil used for the gravimetric analysis.     

Comparison of different methods for the determination of the oil content in oilseeds

The investigation and assessment of the oil content of oilseeds are important criteria, especially for the oil milling trade. Standard methods for the determination of the oil content of oilseeds are very time consuming, with extraction periods of 4 to 8 h. Three different oilseeds—rapeseed, sunflower, and soybean—are extracted by supercritical fluid extraction (SFE), accelerated solvent extraction, microwave-assisted extraction, solid fluid vortex extraction, and Soxtherm, and the results are compared with the result of the German Fat Science Society (DGF) standard method B-I 5 (87). Besides, the extracts are analyzed regarding the content of tocopherols as a parameter for mild extraction conditions and the content of diglycerides and free fatty acids as parameters for the content of more polar lipids. The results of the determination of the oil content under optimal conditions are comparable with the results of the DGF standard method B-I 5 (87). There are no significant differences between the different methods. The content of tocopherols is dependent upon the extraction method and the type of oilseed. The highest content is obtained by SFE. The content of diglycerides and free fatty acids varied according to the oilseed.     

Total oil analysis of soybeans by simultaneous grinding and solvent extraction

A new, rapid method for total oil analysis of soybeans is proposed in which ground soybeans are mixed with solvent and further ground in a closed homogenizer until the oil is completely dissolved. A sample of the slurry can then be filtered and the oil content determined by evaporating the solvent from a measured amount of miscella. Parameters studied included times and speeds needed to produce sufficiently small particles so that all the oil was dissolved. The new analysis compared favorably with conventional Goldfisch extraction for total oil of soybeans. Preliminary experiments indicated that rapeseed could be extracted by the new procedure without preliminary grinding. Published with the approval of the director of the Arkansas Agricultural Experiment Station.     

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.     

Total phospholipids in crude palm oil: Quantitative analysis and correlations with oil quality parameters

Phospholipids, selectively extracted from crude palm oil and free of colored carotenoids, can be quantitatively determined by the phospholipid-molybdenum blue complex in hexane. A study of the phospholipid in crude palm oil in relationship to other components affecting oil quality shows that they have a beneficial effect while any detrimental effect may be of an indirect nature.     

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.     

Analysis of oilseeds for protein,oil, fiber and moisture by near-infrared reflectance spectroscopy

Wavelength and mathematical treatments were optimized for the determination of oil, protein, moisture and crude fiber components in the ground seeds of nine oil-bearing crops [rape, flax, sunflower, safflower sesame, palm kernel, groundnut (peanut), soybean spectroscopy. Optimum wavelengths, selected for the estimation of various components, were influenced by the algorithm (math treatment) used and differed among crops. The second derivative math appeared to be better suited for the estimation of all constituents. Methods for sample preparation of all constituents. Methods for sample preparation and analytical results are discussed. The accuracy was quite satisfactory for routine quality control and evaluation purposes, and precision was equal to that of standard analyses.     

Breeding for improved oilseeds

Breeding for improved oilseeds has traditionally emphasized improvement in yield, oil content and disease resistance. Improved protein has been sought by some breeders in recent years. The soybean varieties Provar and Protana were released in 1969 because they contain higher protein percentages than other varieties. Glandless cotton varieties are being bred by public and private breeders. Two glandless varieties have been released by commercial breeder-seedsmen, but one has been withdrawn because of low yield. It probably will be several years before glandless varieties are of commercial significance. Safflower germplasm has been screened and a source of improved lysine has been identified. This lead may be pursued, but major problems of disease susceptibility and high fiber content also demand attention. Emphasis in sunflower programs will be on developing higher yielding lines and on exploiting the possibility of developing hybrids. Sunflower research personnel is so limited that there is not likely to be any major effort on quality factors for some time. Sesame research is very limited, major emphasis being on control of shattering. One of 21 papers presented at the Symposium, “Oilseed Processors Challenged by World Protein Need,” ISF-AOCS World Congress, Chicago, September 1970.     

Total fatty acid analysis of vegetable oil soapstocks by supercritical fluid extraction/reaction

Soapstock from vegetable oil refining operations is a value-added by-product that finds further industrial use based on its fatty acid content. Since the fatty acid content of soapstock can vary according to its vegetable oil source or method of refining, determination of its total fatty acid (TFA) by an accurate analytical method is of key importance to purchasers of this refinery by-product. Traditionally, the TFA content of soapstock has been determined by the AOCS Official Method G3-53 based on a gravimetric assay. Unfortunately, this gravimetric-based assay requires considerable time and incorporates a considerable quantity of organic solvent per assay. In this study, the authors have applied supercritical fluid extraction (SFE) with an enzymatic-based reaction (SFR), in the presence of supercritical carbon dioxide (SC-CO₂), to determine the TFA content of soapstocks. The SFE/SFR sequence was conducted using two commercially available extractors using an in situ supported lipase in the extraction cell to form fatty acid methyl esters (FAME). Gas chromatographic (GC) determination of the individual FAME, followed by quantitation based on the calculated sum of all the fatty acids from the GC analysis, allowed a precise determination to be made of the soapstock’s TFA content. The TFA contents of three different soapstocks determined by this method were slightly higher than the values derived from Official Method G3-53. The reported method takes less than one-half of the time of Official Method G3-53 and reduces organic solvent use from 575 mL to under 2 mL of solvent by using SC-CO₂.     

Recovering water-immiscible solvents from oilseeds

Journal of the American Oil Chemists' Society - Processes used in desolventizing are reviewed. Anomalous high residuals in desolventized, deodorized and toasted flakes can be accounted for by...     

Decorticating linseed and other oilseeds

A unique model huller capable of effectively decorticating linseed and other small oilseeds was developed. On linseed, a yield of 25 to 30% of apparently clean hulls was obtainable, but the hulls had an inherently high oil content ranging from 16 to 25%. Altho the oil in hulls has approximately the same iodine number and drying time as the kernel oil, it appears to be characteristic of the hull structure rather than absorbed from the kernel. Decorticating hempseed with this same huller noticeably improved the oil color, and materially improved the protein content and appearance of the cake. Good decorticating results were also obtained with this huller on cantaloupe seed, rapeseed, and some varieties of mustard seed. Tests on perilla were inconclusive.     

Modeling the solvent extraction of oilseeds

A computer model and an experimental procedure for generating data needed in the model have been developed for the oilseed extraction process. The experiments are relatively simple and are performed with a bench-top extractor. Experimental results and modeling calculations are presented for the extraction of cottonseed using hexane, isopropanol and ethanol. The calculations show that in an alcohol extraction using a chill separation, isopropanol’s greater oil miscibility allows for a lower solvent-to-feed ratio than does ethanol. Using the latter solvent, however, achieves lower residual lipids in the extracted meal because recycled ethanol contains less oil than recycled isopropanol. Presented in part at the AOCS meeting in Honolulu, HI, in 1986.     

Trace element composition of common oilseeds

Nineteen varieties of groundnut(Aracbis bypogea), 8 of mustard(Brassica nigra), 9 of coconut(Cocos nucifera), and 6 each of sesame(Sesamum indicum) and safflower(Carthemum tinctorius) were analyzed for total ash and 9 mineral nutrients. Varietal dif-ferences were significant in magnitude for zinc in sesame-, for man-ganese, molybdenum and chromium in mustard; for calcium, iron, manganese, copper, molybdenum and chromium in groundnut; for calcium, molybdenum and chromium in safflower; and for calcium, iron, copper and molybdenum in coconut. Sesame was the richest source of most of the inorganic nutrients.