Functional and conformational characterisation of walnut protein obtained through AOT reverse micelles

Walnut protein was extracted from defatted walnut flour by bis (2‐ethylhexyl) sodium sulfosuccinate (AOT) reverse micellar system and alkali solution with isoelectric precipitation. The functional and conformational characteristics of two proteins were investigated and compared. Walnut protein obtained through AOT reverse micelles was found to have higher extraction yield, solubility, emulsifying activity, foam capacities, water‐ and oil‐holding capacity compared to the protein from alkali solution along with isoelectric precipitation, while the surface hydrophobicity (H₀), contents of disulphide bond (SS) and sulfhydryl group (SH) were relatively lower. The differences of H₀, SS and SH contents could be due to the conformational changes of walnut proteins using two extraction methods. FTIR spectra and data showed that the reverse micelles caused the decrease in α‐helix, β‐sheet, random and β‐turn of walnut protein, the increase in the side‐chain structure content, which could be responsible for the modification of functional properties.     

Effects of AOT reverse micelle on properties of soy globulins

This study was focused on the influence of AOT reverse micelle on physical–chemical properties of 7S and 11S globulins from soy proteins, and compared with aqueous buffer extraction. The results showed that the contents of the surface hydrophobicity and SH groups of 7S and 11S globulins and SS bonds of 11S globulin, using AOT reverse micelle extraction, were augmented, and SS bonds of 7S globulin decreased. The thermal and rheological properties of 7S and 11S globulins extracted using the two methods were studied by differential scanning calorimetry (DSC) and rheometery. It was found that the peak denaturation temperature and heat of transition of 7S and 11S globulins with aqueous buffer extraction were different from that with AOT reverse micellar extraction. The AOT reverse micelle did not affect the gel properties of 11S globulin, while it influenced 7S globulin’s. Hardness, springiness, gumminess, adhesiveness and chewiness of 7S globulin from AOT reverse micelle were lower than that from aqueous buffer extraction, but gumminess was higher.     

Effects of extraction temperature,ionic strength and contact time on efficiency of bis(2‐ethylhexyl) sodium sulfosuccinate (AOT) reverse micellar backward extraction of soy protein and isoflavones from soy flour

BACKGROUND: Soy protein enriched with isoflavones has been linked to various disease‐preventing and health‐promoting activities owing to the antihypertensive, hypocholesterolaemic, antiobesity and antioxidative properties of isoflavones. The isoflavone profiles of soy‐based products are known to be highly dependent on the various chemical and physical treatments to which the products have been subjected. The aim of this research was to increase the efficiency of backward extraction of soy protein and isoflavones from bis(2‐ethylhexyl) sodium sulfosuccinate (AOT) reverse micelles by studying the effects of extraction temperature, ionic strength of the aqueous stripping solution and contact time on the amounts of soy protein and isoflavones backward extracted from an AOT/H₂O/isooctane reverse micellar system. RESULTS: By modifying the extraction temperature, ionic strength and contact time, 47.0–60.2% of protein, 43.3–68.4% of daidzin, 43.8–74.6% of genistin, 39.0–88.8% of glycitin, 20.8–92.6% of malonyl genistin, 20.2–52.0% of malonyl glycitin, 32.7–75.6% of acetyl genistin, 49.7–76.8% of daidzein and 19.6–38.1% of genistein present in the AOT reverse micellar solution were backward extracted into the aqueous stripping phase. Statistical analysis showed that there were significant linear and interactive effects of temperature and contact time on the backward extraction of daidzin, genistin, glycitin and daidzein. Significant linear and interactive effects of ionic strength and contact time were found in the backward extraction of daidzin and genistin. The backward extraction of genistein was only influenced by contact time and its interaction with temperature. CONCLUSION: This study showed the potential of reverse micelles as a protocol for extracting isoflavones from soy samples for analytical purposes. By modifying the extraction temperature, contact time and ionic strength, soy protein enriched with daidzin, genistin, daidzein and genistein could be produced from soy flour. The results represent an important contribution to current knowledge on utilising reverse micellar extraction in food technology. Copyright © 2007 Society of Chemical Industry     

Storage induced changes to high protein powders: influence on surface properties and solubility

BACKGROUND: MPC 80 is a high‐protein (80%) milk powder commonly used in the food industry as a functional ingredient and valued for its nutritional quality. However, its rehydration properties decline during storage, causing more time to be required for rehydration of the powder by the end user. It is thought that changes at the surface of the powder particles contribute to this reduced solubility during storage. RESULTS: Surface composition and structural changes in milk protein concentrate (MPC) were observed during 90 days of storage at temperatures of 25 and 40 °C and relative humidities of 44, 66 and 84%. No significant changes to the surface composition (fat, protein and lactose) of the MPC powder samples occurred during storage; however, some changes in the microstructure of the powders were observed. Scanning electron microscopy analysis of the powder particles during dissolution showed the formation of a crust, consisting of a thin layer of fused casein micelles, on the surface of the stored powders. An increase in the hydrophobicity at the surface of the particles was evident by X‐ray photoelectron spectroscopy analysis of the bonding state of the elements at or near the surface and by atomic force microscopy measurements of the adherence of particles to the surface of a material. CONCLUSION: The development of this ‘crust’ is thought to contribute to the decrease in the solubility of the powder particles during storage. The increase in the hydrophobicity at the surface and the casein micelle interactions resulting in the surface crust formation appear to contribute to the decrease in the solubility of MPC during storage. Copyright © 2011 Society of Chemical Industry     

反胶束萃取豆油对脂肪酸成分的影响

用AOT/异辛烷反胶束体系从全脂豆粉中同时分离大豆蛋白和油脂;考察了预处理、加酶、温度、WO值对脂肪酸(FA)组分的影响。结果表明,反胶束萃取时对FA组分影响不大,除WO外,各因素几无影响,WO对FA影响较大,可能与AOT残留有关。     

反胶束提取小麦胚芽蛋白的工艺研究

以副产品小麦胚芽为原料,用反胶束法研究了小麦胚芽蛋白的提取条件,包括前萃和后萃。前萃由琥珀酸二(2-乙基己基)酯璜酸钠(AOT)-异辛烷-氯化钾缓冲溶液组成的反胶束体系从小麦胚芽中提取蛋白;后萃先回收异辛烷,少量KCl的缓冲溶液溶解剩余的固形物,最后用丙酮沉淀得小麦胚芽蛋白。通过单因素实验,考查了AOT浓度、萃取时间、加入小麦胚芽粉量、温度、KCl浓度、缓冲溶液pH、W/O对小麦胚芽蛋白前萃率的影响以及KCI浓度、缓冲液pH、缓冲液加入量对小麦胚芽蛋白后萃率的影响。     

酶解辅助反胶束法萃取小麦胚芽蛋白的研究

采用由AOT(琥珀酸二(2-乙基己基)酯磺酸钠)-异辛烷-KCl缓冲液组成的反胶束体系,联合酶解技术提取小麦胚芽蛋白。探索了酶与底物浓度比、时间、缓冲液pH、温度四个因素对蛋白质前萃率的影响。结果表明:酶解辅助反胶束萃取蛋白是可行的,可以显著提高前萃率,最佳酶与底物浓度比为0.23AU/gPro、时间8h、缓冲液pH8.10、温度60℃。     

不同干燥技术对核桃粕蛋白粉品质特性及微观结构的影响

以核桃粕为原料,采用热风干燥、热泵干燥、真空冷冻干燥和喷雾干燥4 种干燥技术制备核桃粕蛋白粉,考察不同干燥技术对核桃粕蛋白粉品质特性及微观结构的影响。结果表明：热风和热泵干燥制备的核桃粕蛋白粉吸水率较低,易贮藏,但色泽和品质较差,呈现大小不一的不规则块状结构,且表面结构粗糙;真空冷冻干燥获得的核桃粕蛋白粉集粉率、蛋白质量分数和必需氨基酸、总氨基酸含量均为最高,分别为29.18%、87.70%和24.61、86.11 g/100 g,水分质量分数最低（3.05%）,但粉体色泽不佳,呈表面光滑的片层微观结构、颗粒较大;喷雾干燥制备获得的核桃粕蛋白粉虽集粉率最低,但感官评价总分、L*值、水分质量分数、比表面积、吸水率最高,分别为75 分、90.63、3.91%、271.47 m2/kg、2.16%,营养品质较好,润湿性最小（139.33 s）,粒径小且均匀,微观结构保持较好。综合考虑核桃粕蛋白粉品质特性、微观结构、干燥效率及生产能耗,喷雾干燥是制备核桃粕蛋白粉的最佳选择。     

酶解辅助反胶束法萃取小麦胚芽蛋白前萃工艺的优化

采用由AOT(琥珀酸二(2-乙基己基)酯磺酸钠)-异辛烷-KC l缓冲液组成的反胶束体系,联合酶解技术提取脱脂小麦胚芽蛋白。探讨了反应时间、缓冲液pH、酶加量3个因素对蛋白前萃率的影响,并用响应面优化前萃工艺条件。经响应面分析得到稳定点为鞍点,采用岭嵴分析进一步优化得到最佳小麦胚芽蛋白前萃工艺条件为:反应温度40℃,反应时间1 h,缓冲液pH 9.22,酶加量0.153 AU/g。在此最佳工艺条件下,蛋白前萃率达到76.99%。     

反胶束萃取技术制备大豆蛋白组分的电泳法研究

对不同条件下丁二酸二异辛酯磺酸钠(AOT)/异辛烷反胶束溶液萃取的大豆蛋白进行电泳分析,同时考察反胶束萃取与碱溶酸沉法生产大豆蛋白产品组分的差异.蛋白产品组分分析表明,随着反胶团"水池"半径的减小,反胶束能萃取较大的大豆蛋白质亚基的比例有明显的减小;大豆分离蛋白与反胶束萃取的大豆蛋白所含的亚基比例有明显的差别.     

Kinetics of Protein Extraction in Reverse Micelle

Sodium bis (2-ethylhexyl) sulfosuccinate (AOT)-sodium dodecyl sulfate (SDS)/isooctane-octanol reverse micelle extraction was tested an efficient and effective approach to separate peanut protein from full-fat peanut powder. Here, important kinetic factors including pH, ion strength, and temperature were studied during reverse micelle backward extraction. The extraction conditions were obtained by response surface experiments as follows: pH 7.5, ion concentration 1.1 mol/L at temperature 35°C. Under these optimum extraction conditions, the extraction rate of protein reached 79.03%. A model on the kinetic partitioning of peanut protein was also developed. The backward extraction in this reverse micelle system was controlled by interfacial resistance instead of diffusion resistance in reverse micelle and aqueous phase with the total mass transfer rate of 0.8×10^?5 m³·s^?1. A two-film theory may be the mechanism for flat interface. Results of mass transfer process are helpful for creating an reverse micelle extraction process, and used for purification of peanut proteins, promoting the development of food industry.     

Extraction and physicochemical properties of soya bean protein and oil by a new reverse micelle system compared with other extraction methods

Reverse micelle extraction is a novel technology for the separation of plant components such as proteins and oil. In this study, sodium bis(2‐ethylhexyl) sulphosuccinate (AOT) reverse micelle system and AOT/Tween 85 reverse micelle system were used to extract soya bean protein and oil from soya bean flour. The physicochemical properties of the protein and oil extracted were investigated and compared with traditional extraction methods. The results showed that the efficiency of forward extraction of soya bean protein using an AOT/Tween 85 reverse micelle system was superior to that using an AOT reverse micelle system at the optimal extraction conditions. In addition, soya bean proteins extracted using reverse micelle extraction had no unordered structure under Fourier transform infrared spectroscopy. The acid and peroxide values of oil products from two reverse micelle extractions were lower than that from immersion. The results indicated that AOT/Tween 85 reverse micelle system is effective in extracting soya bean protein and oil.     

皮蛋壳表层红色斑块成分的分析与鉴定

目的 分析鉴定皮蛋壳表面红色斑块物质组成成分, 为控制红斑生成提供理论依据。方法 采用场发射扫描电镜(Scanning Electron Microscope, SEM)、X射线衍射仪(X-ray Diffractometer, XRD)、X射线电子能谱仪(X-ray Photo-electron Spectroscopy, XPS)分析皮蛋壳表面红色斑块的微观结构和化学成分。结果 皮蛋壳表面红色斑块物质是大块片状物附着在粗糙的碳酸钙晶体外层, 蛋壳气孔也被块状异物堵塞, XPS检测出红斑由C、O、N、Na、Ca、Fe、Cu、S、Zn、P等元素组成, Fe元素含量低, 未检出Pb元素; XRD分析确定红斑的主要物质是Cu2O, 红斑外层Cu+因氧化而成Cu2+。结论 皮蛋壳表面红色斑块主成分为Cu2O。采取鸭蛋消毒控菌, 低温避光腌制或许可控制蛋壳红斑形成。     

不同电解质溶液对反胶束萃取花生蛋白的影响研究

研究了KCl、NaCl、LiCl、MgCl2、NaNO3、KNO3、Na2SO4、MgSO4 8种不同的电解质对AOT/正己烷反胶束溶液萃取低温花生粕中花生蛋白的影响,对反胶束的含水量、蛋白质的提取率及通过SDS-PAGE电泳试验对蛋白质的亚基条带进行了比较。试验结果表明,电解质的种类会影响反胶束的含水量;阴离子与阳离子对反胶束溶液萃取大豆蛋白的前萃与后萃都有影响,电解质KCl和NaCl溶液所提取的蛋白质得率较高,分别为54.22%和50.19%;不同的电解质可以影响所得蛋白的亚基组成,可以用来分离不同的蛋白。     

核桃蛋白的组成、制备及特性研究进展

核桃蛋白是制备核桃油脂的主要副产物,目前还没有得到充分的利用。为了促进其在食品领域的应用,人们对其进行了广泛深入的研究,增加了人们对核桃蛋白的理解。本文对其研究现状进行了综述,主要包括核桃蛋白的组成与结构,氨基酸的组成及营养价值,核桃蛋白粉、核桃蛋白浓缩物、核桃蛋白分离物的制备方法与特性,核桃蛋白的物理、化学及酶法改性及对功能特性的影响。最后概述了用核桃蛋白制备核桃乳、核桃蛋白粉及核桃蛋白多肽的最新进展。     

AOT反胶束体系萃取大豆蛋白质的研究

研究了AOT反胶束萃取大豆蛋白的工艺,针对影响AOT反胶束萃取大豆蛋白质的各种因素如反胶束直径、缓冲溶液pH值、离子强度、温度、萃取时间进行了研究,得出主要的影响因素为反胶束直径、缓冲溶液pH值和离子强度,并得到最佳的萃取条件为:反胶束直径为4.9nm,此时的Wo值为15.8;pH值为6.5;离子强度为0.1mol/L;萃取温度为45℃;萃取时间为20min。在此条件下蛋白质的萃取率为82.57%。     

低温等离子体处理对PET膜性能的影响

选用低温等离子体处理对PET膜进行表面改性.通过扫描电镜、XPS、表面接触角以及表面自由能分析,测试表征了等离子体处理前后膜表面物理形貌结构、化学组分构成以及表面性能的变化情况.研究结果表明,等离子体处理对PET膜产生刻蚀作用,等离子体处理后的样品表面氧/碳、氮/碳含量比有所增加,膜表含氧极性基团如C—O/C—N、C O、C O—O等的含量增加,膜表亲水性有明显改善,表面自由能明显提高.     

喷雾干燥与真空冷冻干燥对核桃粕红枣复合粉品质的影响

以核桃粕、红枣为原料,采用喷雾干燥、真空冷冻干燥2种方式制备核桃粕红枣复合粉,对其集粉率、水分含量、蛋白质含量、堆积密度、流动性、溶解性、色差值、微观结构、蛋白质体外模拟消化、热稳定性进行探究。结果表明:真空冷冻干燥集粉率明显高于喷雾干燥,但是耗时长,水分含量和堆积密度高于喷雾干燥,休止角低于喷雾干燥,说明真空冷冻干燥核桃粕红枣复合粉不易贮藏、溶解性较差,但是流动性好;喷雾干燥所得复合粉颜色比较鲜亮。2种复合粉热稳定性相似,但从整体来看,喷雾干燥复合粉蛋白质营养价值更高。观察复合粉微观结构,喷雾干燥复合粉呈球状,有利于颗粒与水分接触;真空冷冻干燥复合粉形状不规则,颗粒之间出现黏结,不利于颗粒与水分接触。     

Effect of drying and proline addition on aroma volatile compounds of acid‐hydrolysed rice bran protein concentrate

Rice bran protein concentrate (RBPc) was hydrolysed by 0.5 N aqueous HCl at 95 °C for 12 h. The liquid hydrolysate obtained was prepared as hydrolysate powder by spray drying. Aroma volatile compounds in liquid hydrolysate and its hydrolysate powder were tentatively identified by GC‐MS. Furfural and vanillin were found in both hydrolysates with high concentration, and vanillin showed the highest odour activity value. Hexanal was present in only liquid hydrolysate. Concentrations of carboxylic acids and heterocyclic compounds, especially 2‐methoxy‐6‐methylpyrazine, increased after drying. Amino acid composition of the hydrolysate powder showed high aspartic acid and glutamic acid. Aroma volatile compounds of hydrolysate powder prepared by the addition of proline at pH 6.0 (Pro6.0‐H) and pH 7.5 (Pro7.5‐H) before drying were investigated. Furaneol was found only in Pro6.0‐H, but it was not detected in Pro7.5‐H and hydrolysate powder without proline addition. Pro7.5‐H had higher furfural and vanillin concentrations than Pro6.0‐H.     

萃取方法对樟树叶萃取效果的XPS表征

以樟树叶为研究对象,通过超临界萃取和微波萃取两种方法对其进行处理并采用X射线光电子能谱仪(XPS)对处理后的樟树叶残渣表面化学组成和结构变化进行表征,以期对提取效果进行预测。结果表明,处理前后的樟树叶表面主要由C、O、N、Si等元素组成。通过对C1s进行曲线拟合与分峰发现,处理前后的樟树叶中的C1s存在三种形态:C1、C2、C3。C1的相对含量的变化为:微波萃取后的樟树叶<超临界萃取后的樟树叶;C2、C3的相对含量变化规律与C1正相反。对于处理前后樟树叶表面O1s拟合分峰发现其有两种结合形式:O1和O2。由于樟树叶中不仅含有C元素,还含有N、Si元素,因此,经超临界和微波两种方法处理后樟树叶中O1的含量较素材有所提高。经微波处理后的萃取液中的萜类化合物等抽提物含量高于超临界萃取;经超临界萃取的挥发油中含有抽提物的同时也含有大量的葡萄糖类化合物。可根据提取物的不同用途采用不同的处理方法。