Influence of particle size on protein extractability from soybean and okara

Nitrogen Solubility Index (NSI) of okara was 38 which was only about half of soybean (71). Maximum protein recovery of 97.0% and 93.4% was achieved with soybean and okara flour from their respective fine fractions (<75 μm) in a three-step-sequential extraction. Recovery of protein from unclassified primary ground flour of soy and okara was much lower compared to their corresponding fine fractions (particle size <75 μm). Secondary grinding of coarse fraction improved the overall protein recovery to an extent of 3.3% in okara and to a much larger extent of 6.8% in soybean. Results showed that a two-step sequential extraction with respective solid-to-solvent (w/v) ratios of 1:20 and 1:10 was suitable in terms of protein recovery. Protein recovery from soy granules and okara flakes improved by 30.6% and 6.9%, respectively with the introduction of primary and secondary grinding steps indicating the benefits of the proposed approach for practical applications.     

Production of okara and soy protein concentrates using membrane technology

Microfiltration (MF) membranes with pore sizes of 200 and 450 nm and ultrafiltration (UF) membranes with molecular weight cut off of 50, 100, and 500 kDa were assessed for their ability to eliminate nonprotein substances from okara protein extract in a laboratory cross-flow membrane system. Both MF and UF improved the protein content of okara extract to a similar extent from approximately 68% to approximately 81% owing to the presence of protein in the feed leading to the formation of dynamic layer controlling the performance rather than the actual pore size of membranes. Although normalized flux in MF-450 (117 LMH/MPa) was close to UF-500 (118 LMH/MPa), the latter was selected based on higher average flux (47 LMH) offering the advantage of reduced processing time. Membrane processing of soy extract improved the protein content from 62% to 85% much closer to the target value. However, the final protein content in okara (approximately 80%) did not reach the target value (90%) owing to the greater presence of soluble fibers that were retained by the membrane. Solubility curve of membrane okara protein concentrate (MOPC) showed lower solubility than soy protein concentrate and a commercial isolate in the entire pH range. However, water absorption and fat-binding capacities of MOPC were either superior or comparable while emulsifying properties were in accordance with its solubility. The results of this study showed that okara protein concentrate (80%) could be produced using membrane technology without loss of any true proteins, thus offering value addition to okara, hitherto underutilized. Practical Application: Okara, a byproduct obtained during processing soybean for soymilk, is either underutilized or unutilized in spite of the fact that its protein quality is as good as that of soy milk and tofu. Membrane-processed protein products have been shown to possess superior functional properties compared to conventionally produced protein products. However, the potential of membrane technology has not been exploited for the recovery of okara protein. Our study showed that protein content of okara extract could be improved from approximately 68% to approximately 81% without losing any true proteins in the process.     

亚临界丁烷制备豆粕及其蛋白氧化稳定性研究

采用亚临界丁烷对大豆粉脱油制得豆粕(DSF-B),并与正己烷制备豆粕(DSF-H)比较,对分离蛋白得率及热变性、豆粕残余极性脂和在贮藏过程中蛋白的氧化进行分析。DSF-B的蛋白得率(32.1%)比DSF-H高(约6%),蛋白热变性二者一致,且11S变性温度低于工业白豆片。残余极性脂分析,DSF-B比DSF-H总量低、磷脂含量高,脂肪酸组成有差异。模拟贮藏试验表明,DSF-B在贮藏中蛋白更易被氧化,这可能与极性脂的组成有关。亚临界萃取技术无高温处理、可选溶剂多样,可开发应用于大豆等植物蛋白制品。     

TG酶-MgCl2协同诱导对冷榨豆粉凝胶的影响

摘 要：以冷榨豆粉为原料,研究在转谷氨酰胺酶（transglutaminase,TG酶）与氯化镁（MgCl2）的协同诱导对其形成凝胶的影响。结果表明,以冷榨豆粉为原料制备的豆腐膳食纤维含量约是卤水豆腐3 倍,脂肪含量约为卤水豆腐的1/3;TG酶的加入会明显改善冷榨豆粉凝胶内部水分,使其更为均匀,且制成的豆腐凝胶具有更高的储能模量G’（10 498 Pa）,表明形成更牢固的凝胶网络结构,从而导致MgCl2-TG酶豆腐的持水性最大（51.01%）、出品率最高（244%）;二级结构无规卷曲相对含量最高（21.45%）;维持凝胶网络的二硫键含量（5.46 μmol/g）接近卤水豆腐（7.02 μmol/g）;扫描电镜结果表明TG酶协同MgCl2使冷榨豆粉豆腐凝胶网状更为细致紧密,整体接近卤水豆腐。这表明,TG酶与MgCl2凝固剂协同作用可改善冷榨豆粉形成凝胶的品质,本研究为冷榨豆粉的多元开发提供了一定的理论基础。     

大豆分离蛋白-黄原胶-茶多酚复合物的制备及其乳液性质表征

以大豆分离蛋白（SPI）、黄原胶（XG）、茶多酚(TP)为原料,改变原料的添加顺序制备三元复合物SPI-XG-TP和SPI-TP-XG,研究了不同复合物的结构与乳化特性的差异。结果表明：蛋白质与多糖、多酚复合之后其结构发生一定程度的改变,且复合物的乳化特性都得到了改善,两种三元复合物中SPI-XG-TP稳定的乳液粒径更小,电位绝对值更大,乳化活性更高,但乳化稳定性略低于SPI-TP-XG稳定的乳液。大分子间能够相互交联形成三元复合物并改变蛋白质的结构,不同原料添加顺序的复合物的结合过程不同     

Soybean seeds and its by-product okara as sources of dietary fibre. Measurement by AOAC and Englyst methods

The composition of soybean seeds and its by-product okara has been studied in this work. Dietary fibre was analysed by Englyst et al. method, by enzymatic–gravimetric methods of AOAC and by the quantification of the monomers obtained from the AOAC residues after acid hydrolysis (AOAC plus hydrolysis). Total dietary fibre by the enzymatic–gravimetric methods of AOAC in okara (55.48 g/100 g dry matter) is more than twice that of soybean seeds (24.37 g/100 g dry matter). The proportion IF/SF is 11 in okara and 6 in soybean seeds. Dietary fibre results from enzymatic–gravimetric AOAC methods are higher in okara and soybean seed samples than those from the Englyst method (okara: 41.14 g/100 g dry matter; soybean seeds: 15.05 g/100 g dry matter), and AOAC plus hydrolysis (okara: 44.91 g/100 g dry matter; soybean seeds: 16.38 g/100 g dry matter). In the case of the insoluble fibre from both samples, AOAC plus hydrolysis gives significantly (p < 0.001) higher values than the Englyst method, whilst for soluble fibre the opposite occurs (p < 0.001). The main monomers in soybean seeds and okara fibre are glucose, galactose, uronic acids, arabinose and xylose. The proportion of each monomer is similar in soybean seeds and okara, so the healthy properties of soybean seeds fibre are also claimed for okara.     

豆渣酱制曲工艺条件优化

在制酱工艺中,利用豆渣代替黄豆和豆粕生产酱产品,并通过单因素实验和正交实验确定了优化的制曲条件:湿豆渣和干面粉质量比7:4,高压蒸煮30 min,接种酱油曲精0.05%,制曲室中培养36 h。按照此条件制得的豆渣酱与传统豆酱风味和口感相差不大。实验结果表明,采用豆酱工艺生产豆渣酱为豆渣的有效利用开辟了新的途径。     

Physicochemical and Sensory Properties of Corn Tortillas Made from Nixtamalized Corn Flour Fortified with Spent Soymilk Residue (okara)

ABSTRACT: The chemical study of okara composition and a sensory evaluation study were conducted to determine the effect of okara supplementation on certain physical, chemical and sensory properties of corn tortilla. Dried okara was added at the level of 5,10,15,20, and 25% to nixtamalized corn flour. Due to flavor, enriched tortillas at levels higher than 10% of okara were not accepted. At 10% of okara supplement, lysine and tryptophan content in tortilla were increased from 56 and 70% of FAO profile to 93 and 92% respectively.     

蒸谷米糠蛋白乳化性的研究

研究在不同质量浓度、不同温度、不同pH值、不同离子强度、不同蔗糖质量浓度等条件下,蒸谷米糠蛋白的乳化性和乳化稳定性的变化规律,并和大豆分离蛋白做比较。结果发现:蒸谷米糠蛋白乳化性和乳化稳定性均高于大豆分离蛋白,并变化幅度较大;温度、pH值对蒸谷米糠蛋白乳化性和乳化稳定性影响也较大,pH值接近中性可以平衡乳化性和乳化稳定性相互制约。     

蒸谷米糠蛋白功能特性研究

研究在不同温度和不同pH值条件下,酶解提取的蒸谷米糠蛋白（PRBP）溶解性、乳化性和泡沫性,并和大豆分离蛋白（SPI）做比较。结果发现：在不同温度下,蒸谷米糠蛋白的溶解性、乳化性、泡沫性随温度增加,先升高后下降。而乳化稳定性和泡沫稳定性一直下降;在不同pH值下,蒸谷米糠蛋白的溶解性、乳化性、泡沫性与泡沫稳定性随pH值增加,先降低、后升高,而乳化稳定性先升高后降低;大豆分离蛋白的乳化性和泡沫性好于蒸谷米糠蛋白。     

羧甲基化改性对不同分子量水溶性大豆多糖乳化性的影响

目的研究羧甲基化改性对不同分子量水溶性大豆多糖(soluble soybean polysaccharides,SSPS)乳化性的影响,探索进一步改善水溶性大豆多糖乳化性的方法。方法从豆渣中提取水溶性大豆多糖,使用超滤法分离,获得两种不同分子质量的多糖组分(L-低分子质量,H-高分子质量),分别对SSPS(未分离)、L和H进行羧甲基化改性,通过调节改性条件获得两种不同取代度(D-低取代度,G-高取代度)的水溶性大豆多糖。以不同的水溶性大豆多糖为乳化剂制备乳化液(O/W),对其乳化活性、乳化稳定性和乳化液显微结构进行分析。结果改性前后SSPS(未分离)、L和H的乳化性强弱顺序均为HSSPS(未分离)L;SSPS(未分离)和H的乳化活性在改性之后显著减弱(P0.05),且取代度越高乳化活性越弱,而L的乳化活性在改性之后增强,且取代度越高乳化活性越强;SSPS(未分离)和L的乳化稳定性在改性之后显著减弱(P0.05),但在取代度升高后二者的乳化稳定性又有所改善;H的乳化稳定性在改性之后显著减弱(P0.05),且取代度越高乳化稳定性越弱。结论高分子质量水溶性大豆多糖的乳化性优于低分子质量多糖,且这一规律不受改性的影响。在本试验条件下,羧甲基化改性对不同水溶性大豆多糖乳化性的影响不同,对乳化性的改善有一定的积极作用。     

大豆分离蛋白-花青素复合物的制备及其蛋白结构与功能性质分析

大豆分离蛋白经热处理后与花青素进行复合形成复合物,采用荧光光谱表征复合体系构象变化,以溶解性、乳化性、乳化稳定性、粒度分析及Zeta电位为指标分析该复合体系中大豆分离蛋白二级结构的变化与功能性质表达之间的关系。结果表明：在pH?7.4的条件下,热处理大豆分离蛋白与花青素复合后,大豆分离蛋白的Zeta电位绝对值显著增大,乳化性、乳化稳定性显著提高,但溶解性显著下降。通过荧光光谱分析发现花青素对热处理大豆分离蛋白的荧光猝灭机制为静态猝灭,蛋白与花青素间形成了结合位点数近似于1的复合物,三维荧光光谱结果表明花青素的复合使得蛋白质多肽链的骨架伸展,蛋白结构发生变化。     

Nested PCR detection of genetically modified soybean in soybean flour, infant formula and soymilk

Due to the Brazilian market introduction of the genetically modified (GM) crop Roundup Ready™ (RR) soybean, the ability to detect GM crops has become a legal necessity. In order to detect the presence of RR soybean, a polymerase chain reaction (PCR) amplification method was evaluated for the detection of RR in soybean mixtures and commercially available soy flour, infant formula and soymilk powder. To detect the presence of RR soybean, a nested PCR resulted in an amplicon of 169 bp, present for all soybean mixed samples containing 0.01-10% GM soybean and absent for 0% GM soybean. None of the analysed infant formulas showed a positive signal after the nested PCR; four out of six soy flour samples and 15 out of 25 soymilk powder samples were positive for the presence of RR soybean. Results show that the nested PCR method used is adequate to determine the presence of GM soybean in the presented products.     

不同来源大豆水溶性多糖理化性质的研究

大豆多糖是从豆渣中提取出来的酸性水溶性多糖,具有乳化稳定性、抗黏结性、成膜性等特性,可广泛应用在食品加工中。该文使用红外光谱、紫外-可见光谱和高效液相色谱（HPLC）等仪器,测定国内外不同大豆多糖的分子键类型、紫外-可见光特征吸收、糖组分等理化特性。结果表明,国产1#样品的灰分、黏度、表面张力小,乳化性一般,蛋白、二糖、葡萄糖和果糖的含量相对较高,溶液吸光度值最大;国产2#样品的红外光谱和3#样品相近,但乳化性较差,呈碎片状,与1#、3#样品的近球状差别较大;国外3#样品的表观黏度为90.0～204.3 mPa·s,表面张力介于31.2～51.6 mN/m2,在同等条件下较1#、3#样品高;其乳化性能较好,综合颜色等因素,3#大豆多糖样品的性能最好。     

Germination‐Assisted Enzymatic Hydrolysis Can Improve the Quality of Soybean Protein

This study aimed to investigate the effects of combined germination and Alcalase hydrolysis on the quality of soybean protein. Protein profiles, water solubility, foaming and emulsifying properties, thixotropic properties, and in vitro protein digestibility (IVPD) were tested, the chemical score (CS), essential amino acid index (EAAI), and protein efficiency ratio (PER) of soybean protein were also defined. The combined treatment of germination and Alcalase hydrolysis remarkably improved the solubility, emulsification activity index, emulsion stability index, and foaming capacity of soybean protein. Notably, a decrease in foaming stability was detected. The electrophoretic profile showed a weak breakdown of soybean protein during germination. However, a strong breakdown of protein was observed after the hydrolysis with Alcalase. The combined treatment also decreased the CS and EAAI of soybean protein, but only by 18%. Meanwhile, the IVPD and PER of soybean protein were significantly improved. Moreover, the protein of the germinated and hydrolyzed soybean flour demonstrated better swallowing properties. These findings indicated that the combined treatment of germination and enzymatic hydrolysis can improve the quality of soybean protein.     

大豆蛋白-溶血磷脂O/W型复合乳液的乳化特性

针对大豆溶血磷脂添加量对大豆分离蛋白-溶血磷脂复合乳化体系乳化特性的影响进行探究。对复合乳化体系分别进行了界面蛋白吸附量、界面张力、乳化活性、乳化稳定性、粒径分布、Zeta电位的测定,并采用光学显微镜对乳液中油滴分布及微观结构变化进行观察。结果表明:随着溶血磷脂添加量的增加,乳化特性指标均基本呈现先升高后降低的趋势。其中,当溶血磷脂添加量为10%时,乳液的乳化特性表现最佳,这表明添加适量溶血磷脂会促进其与大豆分离蛋白的相互作用,降低界面张力,在油-水界面上形成较稳定的界面膜,形成稳定的复合乳状液。     

超声处理大豆浆体对提高蛋白质和固形物萃取率的作用

采用低频超声波处理大豆浆体以提高其蛋白质和固形物的萃取率。探讨了处理时间、温度、ｐＨ和超声振幅诸因素对超声处理效果的影响，并初步得出其最佳处理条件。结果表明，采用低频超声波处理大豆浆体及其豆渣能有效地提高蛋白质和固形物的萃取率     

Effects of high-pressure process on kinetics of leaching oil from soybean powder using hexane in batch systems

Mass transfer models of leaching oil from soybean (Glycine max) flour with hexane after high-pressure process (HPP) treatment were developed. High pressure (450 MPa) was applied to the soybean flour (mean diameter of flour particle: 365 μm) for 30 min before leaching the oil components in the solvent. The ratio of solvent (volume, mL) to soybean flour (mass, g), such as 1:10 and 1:20, was employed to characterize the effect of solvent ratio on the leaching rate in the batch type of extraction process. Ultraviolet absorbance at 300 nm was used to monitor the extraction rate. Saturation solubility (C(AS)) was determined to be 21.73 kg/m3. The mass transfer coefficients (k) were determined based on the 1st- and 2nd-order kinetic models. The 2nd kinetic model showed better fit. The HPP treatment showed a higher extraction rate and yield compared to the control, while the amount of solvent did not affect the extraction rate and yield. The scanning electron microscope showed that HPP-treated soybean particles included more pores than the untreated. The pores observed in the HPP-treated soybean flours might help increase the mass transfer rate of solvent and solute in the solid matrix. PRACTICAL APPLICATION: High-pressure processing can help increase the extraction rate of oil from the soybean flour operated in batch systems. The conventional solid to solvent ratio (1:20) used to extract oil composition from the plant seed did not help increase the amount of oil extracted from the soybean flour.     

Altering functional attributes of proteins through cross linking by transglutaminase – A case study with whey and seed proteins

The effect of cross linking of the major whey protein β-lactoglobulin (β-Lg) and major protein fractions (11S) of soybean (Glycinin) and sesame seed (α-globulin) with the microbial enzyme transglutaminase (EC 2.3.2.13) was studied. The formation of polymerized proteins was followed by poly acrylamide gel electrophoresis, gel filtration high pressure liquid chromatography (HPLC) and evaluation of functional properties. Cross linked proteins were less turbid on heating to higher temperature as compared to untreated samples and the temperature at which the protein turns turbid also increased in the treated samples. In case of β-Lg and α-globulin of sesame seed when the control showed turbidity at 60 °C, the enzyme treated sample indicated at 65 °C and higher. Similar results were obtained in the case of soybean also. The treated samples showed higher emulsifying activity when compared to the control. The control showed an emulsifying activity of 0.55 ± 0.02, and the treated sample showed an emulsifying activity of 0.72 ± 0.02 (optical density at 500 nm is taken as emulsifying activity). Foaming capacity did not improve significantly with the enzyme treatment. The complex formed was investigated by gel filtration chromatography. Nearly 30% of the proteins (11S protein fractions and β-Lg) formed the complex and increase in the concentration of the proteins or the enzyme did not show any increase in the complex formation. The changes in the fluorescence intensity indicated changes in the microenvironment of the chromophores induced by the enzymatic cross linking.