Survey of soybean oil and meal qualities produced by different processes

Soybean oil and meal produced by extruding-expelling (E-E) are believed to have unique characteristics compared with products produced by solvent extraction (SE). A survey was conducted to compare quality characteristics of the oils and meals produced from different types of soybean processing methods. Soybean oil and meal samples were collected three different times within a 1-yr period from 13 E-E mills, 8 SE plants, and 1 continuous screwpress (SP) plant. Properties of oil and meal varied considerably between different types of plants and among plants of the same type and sampling times. In general, settled crude E-E and SP oils had significantly greater peroxide values than those of SE oils. E-E oils contained less free fatty acid and phosphorus than did SE and SP oils. The oxidative stability (AOM) of E-E oil was less than that of SE oil, and that of SP oil was intermediate. E-E and SP meals had higher oil and lower protein and moisture contents than those of SE meals. Protein dispersibility indices were lower for E-E and SP meals. Protein solubilities in KOH were similar for E-E and SE meal, but higher than that of SP meal (62%). Rumen bypass protein values were higher for the SP meal.     

Refunctionalization of extruded-expelled soybean meals

Soybean meals produced by extruding-expelling (FF) have poor functional properties due to heat denaturation of the proteins, which limits their utilization in foods. Hydrothermal cooking (HTC), a treatment in which steam (150°C) and high shear are applied to a slurry of soybean meal, was used to refunctionalize EE protein meals. Two EE samples with protein dispersibility indexes (PDI) of 35 and 60 were used, along with solvent-extracted white flakes and full-fat whole soy meal as controls. Two HTC methods were explored: One method used a treatment temperature of 154°C and seven different residence times, controlled by varying the holding tube length; the other involved flashing the treated slurry directly into the atmosphere without any back-pressure regulation or holding. Effects of residence time on functional properties of the samples were investigated. The maximum effect of HTC conducted with the use of holding tubes (with-holding-tube HTC) was also compared with that of flash-out HTC. Solid dispersibility, protein dispersibility, and emulsification capacity of both EE meals were significantly improved by both types of HTC treatments. The flash-out HTC showed more benefits than the with-holding-tube HTC in refunctionalizing heat-denatured EE protein. For example, the solid dispersibility, protein dispersibility, and emulsification capacity of EE meal with PDI of 35 were improved 2.0, 4.4, and 2.1 times, respectively, by flash-out HTC treatment. Therefore, the HTC refunctionalization was proved effective in partially restoring the functional properties of the heat-denatured soy proteins.     

A rapid method for extraction of total lipids from whey protein concentrates and separation of lipid classes with solid phase extraction

A modified procedure for extraction of total lipids from whey protein concentrates was developed such that stable emulsion with extracting solvents was avoided and the solvent system remained monophasic. Nonlipid contaminants from the extract were removed using gel filtration instead of traditional aqueous washing to prevent any loss of polar lipids. The extraction of total lipids by the modified procedure was complete and comparable with a reference procedure. Traditional thin-layer chromatography is tedious and more qualitative than quantitative for lipid class separation. Total lipids were further separated into free fatty acids, phospholipids, cholesterol ester, triacylglycerol, cholesterol, diacylglycerol, and monoacylglycerol, using modified solid phase extraction procedure. Columns with 2 g amino propyl packing allowed separation of up to 80 mg of total lipids into lipid classes gravimetrically. The values for anhydrous milk fat for all lipid classes agreed with those in the literature. Separation of total lipids into lipid classes with solid phase extraction is easy, quantitative, and can also be performed on a preparative scale.     

Analysis of single soybean seeds for oil and protein

Microprocedures were developed to analyze single soybean seeds for protein, oil, and moisture. Ten mature Forrest soybean plants were taken from a yield plot and sampled, so that seeds were taken from the top, middle, and bottom areas. Also, seeds were taken from distal and proximal racemes, from distal and proximal pods on a raceme, and from distal and proximal seeds within a pod. The range in protein for the 241 seeds analyzed was 32 to 51% (dry weight basis) with a standard deviation of 2.96%. The range in oil was 16.5 to 25.5% (dry weight basis) with a standard deviation of 1.84%. The middle area had significantly more oil and significantly less protein than the top and bottom areas. Also, significant differences in protein and oil were found between plants. There was no significant difference in protein or oil due to position of a raceme, position of a pod on a raceme, or position of a seed within a pod. The standard deviation found for protein and oil can be used to estimate the sample size needed to achieve a certain degree of accuracy in protein and oil analyses. To whom correspondence should be addressed at 272 Young Avenue.     

Analysis of soybean lecithins and beef phospholipids by HPLC with an evaporative light scattering detector

Linear (r > 0.99) calibration curves were obtained for 10–150 μg of phosphatidylethanolamine (PE), 10–75 μg of phosphaditylinositol (PI), phosphaditylserine (PS) and lysophosphatidylethanolamine, 10–100 μg of phosphatidic acid (PA) and 10–250 μg of phosphatidylcholine (PC) by high-performance liquid chromatography analyses with an evaporative light scattering detector, a Zorbax 7-μm silica column and gradient elution with two solvents. One solvent (A) contained 415 mL isooctane (IOCT), 5 mL tetrahydrofuran (THF), 446 mL isopropanol (IPA), 104 mL CHCl₃ and 30 mL H₂O; and the other solvent (B) contained 216 mL IOCT, 4 mL THF, 546 mL IPA, 154 mL CHCl₃ and 80 mL H₂O. The gradient in which 100% A linearly changed to 100% B in 20 min followed by 12 min of 100% B and then a linear change to 100% A during 5 min separated PE, PS and PC in soybean lecithins and beef lipids, but failed to resolve PI and PA. In these same samples, less polar lipids were separated from phospholipids (PL) by elution from Bond-Elut silica columns with diethyl ether/hexane (20:80, vol/vol), and PL were recovered by elution with methanol. This procedure is useful for concentration of minor lipid components. Levels of PE, PI-PA, PS and PC were higher in granular than in liquid lecithin, and PC was the most abundant PL in soybean lecithins and beef lipids.     

Preparation of soy protein concentrate and isolate from extruded-expelled soybean meals

Soy protein concentrates (SPC) and soy protein isolates (SPI) were produced from hexane-defatted soy white flakes and from two extruded-expelled (EE) soy protein meals with different degrees of protein denaturation. Processing characteristics, such as yield and protein content, and the key protein functional properties of the products were investigated. Both acid-and alcohol-washed SPC from the two EE meals had higher yields but lower protein contents than that from white flakes. Generally, SPC from an acid wash had much better functional properties than those from an alcohol wash. The SPI yield was highly proportional to the protein dispersibility index (PDI) of the starting material, so the EE meal with lower PDI had lower SPI recovery. The protein content in SPI prepared from EE meals was about 80%, which was lower than from white flakes. Nevertheless, SPI from EE meals showed functional properties similar to or better than those from white flakes. The low protein contents in SPC and SPI made from EE meals were mainly due to the presence of residual oil in the final products. SPI made from EE meals had higher concentration of glycinin relative to β-conglycinin than that from white flakes.     

Interference of polar lipids with the alkalimetric determination of free fatty acid in fish lipids

An examination of the suitability of an alkalimetric method for the determination of free fatty acid (FFA) contents in fats, oils, and lipid extracts was conducted by comparing AOCS method Ca 5a-40 with a method based on a Chromarod-latroscan thin-layer chromatography-flame-ionization detector (TLC-FID) system. The FFA contents determined by the alkalimetric method were consistently higher than the genuine FFA contents obtained by the latroscan TLC-FID method. Phospholipids were found to be the major components that contributed to the alkali-titratable, nongenuine FFA in the total FFA determined alkalimetrically. Contributions from other polar lipid components were smaller, but they dominated as the proportion of phospholipids fell. The other alkali-titratable polar components may include oxidized lipids and their by-products bound to protein fragments. The accurate determination of FFA contents by alkalimetric methods may only be applicable to those commercially refined fats and oils that contain negligible amounts of phospholipids. Corrections for the alkalimetrically determined FFA contents should be made for those fats and oils with relatively high phospholipid contents by correlating the nongenuine FFA contents and the phospholipid contents.     

Pressurized liquid extraction of polar and nonpolar lipids in corn and oats with hexane,methylene chloride,isopropanol, and ethanol

Samples of freshly ground corn kernels and freshly ground rolled oats were extracted via pressurized liquid extraction (accelerated solvent extraction) using four different organic solvents [hexane, methylene chloride (also known as dichloromethane), isopropanol, and ethanol] at two temperatures (40 and 100°C). Lipid yields varied from 2.9 to 5.9 wt% for ground corn and from 5.5 to 6.7 wt% for ground oats. With ground corn, more lipid was extracted as solvent polarity was increased, and for each individual solvent, more lipid was extracted at 100°C than at 40°C. With ground oats, the same temperature effects was observed, but the solvent polarity effect was more complex. For both corn and oats, methylene chloride extracted the highest levels of each of the nonpolar lipid classes. In general, for both corn and oats, icnreasing solvent polarity resulted in increasing yields of polar lipids, and for each solvent, more of each lipid class was extracted at 100°C, than at 40°C. Among the lipids in corn extracts, the phytosterols may be the most valuable, and total phytosterols ranged from about 0.6 wt% in the hot ethanol extracts to about 2.1 wt% in the hot hexane and methylene chloride extracts. Total phytosterols in all oat extracts were about 0.1 wt%. Digalactosyldiacylglycerol was the most abundant polar lipid in the oat extracts; its levels ranged from 1.6 wt% in the cold hexane extracts to 4.3 wt% in the hot ethanol extracts.     

Interlaboratory comparison of soybean protein and oil determinations

Iowa State University coordinated an interlaboratory comparison study of Kjeldahl protein and ether oil extraction methods. Blind duplicates of 10 clean, single-variety soybean samples were sent to 30 laboratories grouped in 3 categories of 10 each in public (government and university), commercial and processor facilities. Five of the commercial laboratories were AOCS-certified. Standard deviations among laboratory means across all samples were 3.87 and 1.82 percentage points (dry basis) for protein and oil, respectively (0.48 and 0.27, respectively, for the AOCS-certified laboratories). The average differences between blind duplicates of a sample were 0.71 percentage points for protein and 0.87 percentage points for oil (0.28 and 0.45, respectively, for the certified laboratories). Average standard deviations across laboratories on an individual sample were 2.37 and 1.71 percentage points for protein and oil, respectively (1.87 and 0.99, respectively, for the certified laboratories.     

Characterization of extruded-expelled soybean flours

In recent years there has been widespread growth in extruding-expelling (E-E) facilities for small-scale processing of soybeans. To compete in a highly competitive market, these E-E operations are looking for ways to optimize production of their oil and meal products for values to their customers. The objective of this study was to determine the ranges of residual oil contents and protein dispersibility indices (PDI) possible with E-E processing of soybeans. We also characterized the partially defatted meal for other factors important in food and feed applications. Residual oil and PDI values ranged from 4.7 to 12.7% and 12.5 to 69.1%, respectively. E-E conditions significantly influenced residual lipase, lipoxygenase (L1–L3), and trypsin inhibitor activities. Chemical compositions were different for whole, dehulled, and reduced-moisture soybeans, with dehulled soybeans tending to produce meals having higher residual oil contents at higher PDI values. It was possible to process soybeans with different characteristics (e.g., moisture content, whole, dehulled) to produce meals and flours with wide ranges of properties, providing E-E operators with opportunities to market value-added products.     

Electrophoretic and functional properties of mustard seed meals and protein concentrates

Defatted meals and protein concentrates from five varieties of mustard seeds (four Brassica spp. and one Sinapis alba) were analyzed for polypeptide composition and functional properties. Nonreducing gel electrophoresis showed that Brassica seeds lacked the 135- and 50-kDa polypeptides that were present in the seeds of the S. alba variety. On the other hand, the 29-kDa polypeptide found in the Brassica seeds was absent from the seed of the S. alba variety. Under reducing conditions, the 135 kDa was not detected in the S. alba variety and the intensity of the 50-kDa polypeptide was severely reduced; in contrast, the intensity of the 29-kDa polypeptide in the Brassica seeds was not affected. Meals from yellow seeds had significantly higher (P≤0.05) protein contents than meals from the brown seeds. The emulsifying activity indexes (EAI) of meals and protein concentrates from the Brassica seeds were significantly higher (P≤0.05) than those obtained for similar products from S. alba sees. It was concluded that the disulfide-bonded 50- and 135-kDa polypeptides may have contributed to increased rigidity of S. alba meal proteins, which resulted in poor EAI when compared to the Brassica meals, which do not contain these polypeptides.     

Effect of lipids on soy protein isolate solubility

Reduced-lipid soy protein isolate (SPI), prepared from soy flour treated so that most of the polar lipids have been removed, exhibited an increase in protein solubility of 50% over that of the control SPI prepared from hexane-defatted flour. Adding lipids from a commercial SPI during processing of reduced-lipid SPI decreased SPI solubility by 46%. The 19% decreased solubility caused by the lipids (primarily phospholipids) was largely recovered by treating the protein with a reducing agent (2-mercaptoethanol). The balance of protein insolubility, caused by the lipids, was attributed to a smaller lipid fraction (approximately 5% of the total lipids). Adding lipids during SPI processing contributed to both the formation of oxidized protein sulfhydryls, incapable of being reduced by 2-mercaptoethanol, and to oxidative deterioration of protein as determined by protein carbonyl contents.     

大豆磷脂及其改性产物在化妆品中的应用

介绍了大豆磷脂的生物特性及化学性质,以及部分改性产物的性质与制备方法。指出大部分大豆磷脂都具有良好的乳化性质,可用做化妆品的乳化剂。     

大豆蛋白木材胶粘剂的研究进展

近年来,在合成高分子胶粘剂受到环保与成本的双重困扰日益显著的背景下,开发新一代环保可持续的木材胶粘剂已刻不容缓。大豆蛋白胶粘剂作为最具应用潜力的天然胶粘剂之一,已经得到了广泛的研究。综述了几种对大豆蛋白进行改性的常用方法,并对大豆蛋白胶粘剂的发展方向进行了展望。     

Characterization of soybean protein isolates The effect of calcium presence

Results of a study of the effect of calcium addition on polypeptide composition, hydrophobicity, sulfhydryl content, thermal stability, enthalpy of denaturation, and water solubility of soybean protein isolates suggest that the addition of small amounts of calcium (1.23–5.0 mg/g protein) induced the formation of α, α′ soluble aggregates, whereas large amounts (5.0–9.73 mg/g protein) induced the selective insolubilization of the glycinin fraction. The addition of this ion also produced thermal stabilization of the soybean proteins, mainly the glycinin fraction, and increased the enthalpy of denaturation. A decrease in the surface hydrophobicity of proteins with increasing calcium content was also observed. The results obtained suggested the existence of specific calcium-soy protein interactions, especially with the glycinin fraction.     

A new approach to genetic alteration of soybean protein composition and quality

Although soybeans produce high-quality meal, modern animal and fish production systems often require synthetic essential amino acid supplements to fortify feed rations. However, biotechnology may enable development of soybeans with naturally adequate levels of certain essential amino acids for advanced feed formulations. One approach involves genetic manipulation of glycinin (11S) and β-conglycinin (7S) contents, the principal components of soybean storage proteins. Because 11S contains more cysteine and methionine than 7S protein, a higher 11S:7S ratio could lead to beneficial changes in the nutritional quality of soybean meal. Although genotypic variation for 11S:7S may be low among soybean [Glycine max (L.) Merr.] germplasm, ratios ranging from 1.7–4.9 were observed among accessions of the wild ancestor of cultivated soybean (Glycine soja Sieb, and Zucc.). Thus, wild soybean germplasm was evaluated as a potential source of genes that govern protein synthesis that may have been lost during the domestication of G. max. Change in the amount of 11S protein accounts for a significant portion of the genotypic variation in protein concentration and composition among wild soybeans. Strong positive correlation exists between the 11S:7S ratio and methionine or cysteine concentration of total protein. Moderate positive associations were found for threonine or tyrosine. A moderate negative correlation was found between lysine and 11S:7S. No association was found for leucine and phenylalanine or for total essential amino acid concentration. Based on these data, G. soja may contain a different complement of genes that influence expression of 11S and 7S proteins than G. max germplasm. Thus, through interspecific hybridization, wild soybeans may be a useful genetic resource for the further improvement of protein quality in cultivated soybeans.     

Determination of water-dispersible protein in soybean oil meals and flours

Summary A method is presented for determination of Water-Dispersible Protein, using a Hamilton Beach Drinkmaster #30 modified to accommodate Waring Blendor blades and cups. The probable sources of error in the method are discussed, and the precision of the method is shown, based on the results obtained in three laboratories using six different Modified Hamilton Beach Blendors. Technical Paper 178, Archer-Daniels-Midland Company.     

Functional properties of soybean and lupin protein concentrates produced by ultrafiltration-diafiltration

Ultrafiltration followed by diafiltration (UF-DF) was evaluated for the production of protein products from partially defatted soybean meal or undefatted lupin (Lupinus albus L.2043N) meal. This study determined the effects of UF-DF on functional properties of the extracted proteins and compared the results with those of protein prepared by acid-precipitation (AP). UF-DF produced only protein concentrates (73% crude protein, dry basis, db), while AP produced protein isolates (about 90% crude protein, db). Soybean protein produced by UF-DF showed markedly higher values for solubilities up to pH 7.0, surface hydrophobicity index, emulsion activity index, and foaming capacity than did the AP soybean protein. UF-DF soy protein was also the most heat-stable among all protein samples tested. With lupin proteins, only the surface hydrophobicity and emulsion activity indices were significantly improved by using UF-DF. UF-DF generally had no adverse effects on, and in most cases even improved, the functional properties of soy protein concentrate produced by this method. UF-DF did not produce a comparable improvement in functional properties of lupin proteins as it did for soybean protein.     

Effect of alkali on the refunctionalization of soy protein by hydrothermal cooking

The effects of hydrothermal cooking (HTC) at alkaline conditions on refunctionalization of heat-denatured protein of extruded-expelled (EE) soy meals and on preparation of soy protein isolate (SPI) from EE soy meal were determined. Two HTC setups, flashing-out HTC (without holding period) and HTC with holding for 42 s at 154°C, were evaluated. Alkali (NaOH) addition dramatically enhanced the refunctionalization of EE meal having an initial protein dispersibility index of 35. The more alkali added, the more refunctionalization occurred. Extensive refunctionalization was achieved at 0.6 mmol alkali/g EE meal, and additional improvement was small with more alkali. For both HTC setups, the solids and protein yields of SPI from alkali-HTC-treated EE meals were significantly higher than those from HTC without alkali addition. The yield of protein as SPI increased from 40 to 82% after HTC treatment at 0.6 mmol alkali/g EE meal compared with no alkali addition. The emulsification capacities of SPI after alkali-HTC were similar to those from HTC without alkali. SPI from holding-tube HTC-treated EE meals had higher emulsification capacities than those prepared by flashing-out HTC.     

乳清废水提取大豆低聚糖的开发和生产

利用大豆蛋白加工中排放的乳清废水开发大豆低聚糖,实验结果表明,该法具有工艺简单、操作安全、产品质量好、生产效率高等优点。