Characterization of the Composition, Physicochemical and Functional Properties of Acid Whey Protein Concentrates

Membrane-processed acid whey protein concentrates were studied for their foaming and emulsifying properties in dilute whey protein solutions and in a 30% fat emulsion. Among the compositional factors and physicochemical characters which significantly correlated with foaming and emulsifying properties were protein hydrophobicity, solubility, free-sulfhydryl content, phosphorus and β-lactoglobulin concentration. Heptane binding was negatively correlated with foam overrun and foam stability of whey protein solutions, whereas, exposed hydrophobicity was positively correlated with overrun in the whipped topping.     

巯基乙醇对大豆分离蛋白热致聚合物界面性质的影响

为探讨β-巯基乙醇对大豆分离蛋白热致聚合物界面性质的影响,以大豆分离蛋白为原料,在pH7.0、90 ℃加热添加和不添加β-巯基乙醇（2 mmol/L）浓度为10 mg/mL的大豆分离蛋白溶液0 h和10 h,制备不同大豆分离蛋白质热致聚合物。观察了大豆分离蛋白、添加β-巯基乙醇大豆分离蛋白、大豆分离蛋白热致聚合物和β-巯基乙醇大豆分离蛋白热致聚合物的微观形态、游离巯基含量的变化,同时比较了起泡能力、泡沫稳定性、乳化活性、乳化稳定性、表面疏水性和浊度的差异。结果表明,大豆分离蛋白和添加β-巯基乙醇大豆分离蛋白呈现无规则状态,大豆分离蛋白热致聚合物为有规则的球状颗粒,而β-巯基乙醇大豆分离蛋白热致聚合物部分形成球状聚合物部分形成无规则聚合物。添加β-巯基乙醇改善了大豆分离蛋白的界面性质。与大豆分离蛋白相比较,添加β-巯基乙醇大豆分离蛋白和添加β-巯基乙醇大豆分离蛋白热致聚合物的起泡能力分别提高了64.56%和95.77%,乳化活性提高的幅度分别为12.94%和14.61%。添加β-巯基乙醇大豆分离蛋白和添加β-巯基乙醇大豆分离蛋白热致聚合物在长时间储藏中表现出良好的乳化稳定性和泡沫稳定性。这种良好的界面性质源于β-巯基乙醇的加入赋予聚合物具有更高的游离巯基含量和表面疏水性。并且本实验建立了4种样品的泡沫稳定性和乳化稳定性随时间变化的Rational函数和Linear函数经验模型,为大豆分离蛋白质的实际应用奠定了理论基础。     

干燥方式对蛋清蛋白理化性质和功能特性的影响

为探究干燥方式对蛋清蛋白（egg white protein,EWP）功能特性的影响及其内在机理,分别通过喷雾干燥与真空冷冻干燥制备蛋清蛋白粉,并对其蛋白结构、理化性质与功能特性进行研究。结果表明,与蛋清液（EWP-C）相比,喷雾干燥使蛋清蛋白（EWP-P）的内源性荧光强度降低,表面疏水性和表面游离巯基含量增大。傅里叶变换红外光谱分析显示,EWP-P的α-螺旋、β-折叠和β-转角分别为16.30%、25.72%和40.23%,冷冻干燥蛋清蛋白（EWP-D）分别为20.43%、24.32%和35.69%。不同pH下,EWP-D的溶解度均高于EWP-P,表面张力小于EWP-P。此外,EWP-P的接触角为99.62°,高于EWP-D（接触角为65.97°）,表明喷雾干燥能显著提高蛋白的疏水性（P<0.05）。EWP-D在不同pH下的乳化性、乳化稳定性以及起泡性均大于EWP-P,但起泡稳定性更小,这与EWP-D较高的溶解性与较低的表明疏水性有关。荧光倒置显微镜及激光共聚焦扫描显微镜分析表明EWP-D乳液的微粒更小,分布更均匀,其稳定性高于EWP-P。综上,喷雾干燥蛋清蛋白的β-折叠结构较多,表面游离巯基含量和表面疏水性较高,具有较好的凝胶性;冷冻干燥蛋清蛋白的表面疏水性较小,且表面张力小、溶解度大,具有更好的乳化能力与起泡性。     

Physicochemical and Functional Properties of Dry and Wet Milling Products of Red Cowpeas

Physicochemical and functional properties of dry- and wet-milled red cowpea flour, protein and starch were evaluated. Bulk density of drymilled red cowpea protein was lower than that of wet-milled protein isolate. Dry-milled starch was darker than wet-milled starch. Gelatinization temperature of starch (64–68–74°C) was quite similar to that of mung bean starch. At water to red cowpea starch ratios of 3:1 and 2:1, DSC thermograms showed a single endotherm with T_o of 68.5–69.0°C, T_p of 73.0–73.5°C, T_m of 79.5–80.0°C, and –ΔH of 4.0–4.6 cal/g starch. Pasting properties of red cowpea starch showed a type C amylogram, similar to mung bean starch. By mixing various quantities of red cowpea starch to tapioca starch pasting properties of the latter could be varied. Water and oil absorptions of cowpea flours increased with the increase in protein contents, as did their emulsifying activity and foaming properties. Emulsion and foam stabilities were quite similar among all the red cowpea products, except for protein isolate which were considerably lower, likely due to a greater degree of protein denaturation during precipitation and drying of the isolate. Composite flours made from mixing wheat and red cowpea flours exhibited dough mixing properties indicative of their potential use in baked products.     

不同品种小麦面筋蛋白的功能性质

以10个品种小麦面筋蛋白为研究对象,研究了不同品种小麦面筋蛋白的持水性、持油性等水化性质,以及起泡性、泡沫稳定性和乳化性等表面性质,并分析了面筋蛋白的游离巯基、二硫键和二级结构。结果表明,面筋蛋白的功能特性在不同品种间存在差异。高筋小麦面筋蛋白的持水性、持油性显著高于低筋和中筋小麦面筋蛋白（P<0.05）,新麦26和师栾02-1面筋蛋白分别具有最强的持水性和持油性（其值分别为356.58%、392.5%）。测试样品中,低筋小麦面筋蛋白具有高的起泡性和表面疏水性,豫保1号面筋蛋白起泡性高达183.33%,而郑麦103面筋蛋白表面疏水性最强（P<0.05）。不同品种小麦面筋蛋白的游离巯基和二硫键含量不同,高筋小麦面筋蛋白含有较高的二硫键,而低筋小麦面筋蛋白游离巯基含量高。此外,高筋小麦面筋蛋白具有较高比例的α-螺旋结构,而低筋小麦面筋蛋白具有高比例的β-折叠和无规则卷曲结构。本研究结果可为面筋蛋白的精深加工和在具体领域的应用提供一定的科学依据。     

Enzymatic and extrusion pretreatments of defatted rice bran to improve functional properties of protein concentrates

This study evaluated effects of enzymatic, extrusion and combined pretreatments on functional and thermal properties of protein concentrates from defatted rice bran to improve their applicability to food formulations. After the pretreatments, protein concentrates were recovered by alkaline solubilisation and isoelectric point precipitation. Water absorption capacity, oil absorption capacity, emulsifying and foaming properties, and thermal stability were determined in protein concentrates. Yields of each pretreatment were above 62% protein. Enzymatic hydrolysis increased all functional properties studied, mainly for emulsifying activity index (an increase of 71.1%) and foaming capacity (an increase of 60.3%). The extrusion affected positively the oil absorption capacity, emulsifying activity index and foaming capacity. The combined process was able to raise the functional properties. The principal component analysis confirmed that 95.5% improvement in functional properties of concentrates had a strong positive correlation with the pretreatments. However, the pretreatments affected thermal stability and the enthalpy of denaturation negatively.     

Functional properties of 8S globulin fractions from 15 mung bean (Vigna radiata (L.) Wilczek) cultivars

The functional properties including solubility, water absorption capacity, oil absorption capacity, foaming properties and emulsifying properties of 8S globulin fractions from 15 mung bean cultivars were investigated in this study. In addition, the effects of pH on solubility, foaming properties and emulsifying properties were studied. The functional properties of the 8S globulin fractions varied significantly among the different mung bean varieties and exhibited better performance in solubility and emulsion stability compared with soya bean 7S protein. A negative correlation was found between water absorption capacity and oil absorption capacity. Remarkable differences in polypeptides constituents were observed in 8S globulin fractions, and the ratio of 11S/8S globulins has a positive effect on water absorption capacity while a negative effect on oil absorption capacity. As a function of pH, the emulsifying activity indexes of the 8S globulin fractions were found to be distinctly dependent on the solubility, while no significant correlation was found between the emulsifying stability and solubility, nor between the foaming properties and solubility. The foaming capacity showed a strong correlation with foam stability.     

冷冻及解冻处理对肌原纤维蛋白理化性质的影响

研究不同的冻结温度（-18 ℃和-50 ℃）和解冻方式（微波解冻、空气解冻及4 ℃解冻）对猪肉肌原纤维蛋白含量和理化特性的影响。结果表明,在不同冻结温度与解冻方式下,肌原纤维蛋白的含量、溶解性、乳化活性、乳化稳定性、起泡性及起泡稳定性均降低,表面疏水性增加。其中,采用-18 ℃冻结,微波解冻处理的肌原纤维蛋白与对照组相比,其溶解性、乳化性、乳化稳定性、起泡性及起泡稳定性分别降低了38.7%、16.5%、28.3%、39.6%和17.3%;采用-50 ℃冻结,4 ℃解冻的蛋白其含量（6.32%）、溶解性（22.05%）、乳化性（7.89 m2/g）、乳化稳定性（32%）、起泡性（30.95%）及起泡稳定性（62.25%）与其他处理对应的各指标相比,理化特性均保持较好。不同的冷冻和解冻条件下,肌原纤维蛋白各指标之间的变化相互关联。     

Enhancement of Functional Properties of Rice Bran Proteins by High Pressure Treatment and Their Correlation with Surface Hydrophobicity

Changes in functional properties of rice bran proteins as influenced by high-pressure (HP) treatment (100–500 MPa, 10 min) were studied. Properties evaluated were protein solubility, water absorption capacity, oil absorption capacity, foaming capacity, foam stability, emulsifying activity, emulsion stability, least gelation concentration, and surface hydrophobicity. HP treatment at 100 and 200 MPa significantly improved the solubility and oil absorption capacity, while water absorption and foaming capacities increased further reaching the maximum at 500 MPa. Compared with the untreated control sample, the emulsifying activity and foam stability of treated samples were significantly higher and least gelation concentration was lower, but none of them showed any specific trend with pressure level. Emulsion stability and surface hydrophobicity increased with the pressure level until 400 MPa and decreased slightly at 500 MPa. Pearson correlation coefficients clearly showed that surface hydrophobicity was positively correlated with water absorption capacity, foaming capacity, emulsifying activity index, and emulsion stability index, but negatively correlated with least gelation concentration. The pressure treated rice bran protein possessed good functional properties for use as a food ingredient in the formulations.     

Relationship of hydrophobicity and solubility with some functional properties of cowpea (Vigna unguiculata) protein isolate

The relationship of hydrophobicity and solubility with some functional properties of cowpea protein isolate was determined. Cowpea protein isolate was prepared by alkali extraction followed by precipitation at pH 4.5. The precipitated proteins were then neutralized to pH 7. Heating of the protein isolate to 100°C for 10 min followed by cooling to room temperature resulted in a significant (P ≦ 0.05) decrease in aromatic hydrophobicity (ARH) when compared to the native protein isolate. The inclusion of sodium dodecyl sulfate (SDS) during heating gave a significant (P ≦ 0-05) 1.7-fold increase while inclusion of mercaptoethanol (ME) gave a significant (P ≦ 0.05) 2.5-fold increase in ARH of the cooled protein solution. Protein solubility (PS), foam expansion (FE) and emulsification activity index (EAI) of the isolate generally increased significantly (P ≦ 0.05) upon heating or treatment with urea or SDS or a combination of SDS and ME. Backward stepwise multiple regression was used to obtain equations for predicting emulsifying and foaming properties of the protein isolate from solubility and hydrophobicity parameters. PS, ARH and aliphatic hydrophobicity (ALH) were important in predicting foam stability and emulsion stability, while PS and ALH were important for predicting FE. ALH alone was important for predicting EAI.     

Lupinus mutabilis: Composition,Uses, Toxicology,and Debittering

Lupinus mutabilis has protein (32.0–52.6 g/100 g dry weight) and lipid (13.0–24.6 g/100 g dry weight) contents similar to soya bean (Glycine max). The Ω3, Ω6, and Ω9 contents are 1.9–3.0, 26.5–39.6, and 41.2–56.2 g/100 g lipid, respectively. Lupins can be used to fortify the protein content of pasta, bread, biscuits, salads, hamburgers, sausages, and can substitute milk and soya bean. Specific lupin protein concentrates or isolates display protein solubility (>90%), water-absorption capacity (4.5 g/g dry weight), oil-absorption capacity (3.98 g/g), emulsifying capacity (2000 mL of oil/g), emulsifying stability (100%, 60 hours), foaming capacity (2083%), foaming stability (78.8%, 36 hours), and least gelation concentration (6%), which are of industrial interest. Lupins contain bitter alkaloids. Preliminary studies on their toxicity suggest as lethal acute dose for infants and children 10 mg/kg bw and for adults 25 mg/kg bw. However, alkaloids can also have medical use for their hypocholesterolemic, antiarrhythmic, and immunosuppressive activity. Bitter lupins can be detoxified by biological, chemical, or aqueous processes. The shortest debittering process requires one hour. This review presents the nutritional composition of lupins, their uses (as food, medicine, and functional protein isolates), toxicology, and debittering process scenarios. It critically evaluates the data, infers conclusions, and makes suggestions for future research.     

Influence of extraction methods on functional properties of protein concentrates prepared from South African bambara groundnut landraces

Functional properties of protein concentrates prepared from three bambara groundnut landraces using acid precipitation and salt solubilisation methods were evaluated. The protein content of bambara grains (26–27%) was similar for the three landraces. The acid precipitation gave a much higher yield of protein concentrates (52%), which were also high in protein (79%) compared to the salt solubilisation method (yield: 25%, protein content: 57%). Functional properties of proteins were more influenced by the methods of preparation rather than the landraces. Protein concentrate prepared by salt solubilisation method showed higher emulsifying (63–66%), foaming (53–57%), water (1.4–2.0 mg mL^?1) and oil absorption properties (2.2–2.6 mg mL^?1) than the acid‐precipitated concentrates (53–57%, 63–66%, 2.0–2.7 mg mL^?1, 1.4–1.7 mg mL^?1). The foaming capacity and stability of all the protein concentrates decreased with increasing pH from 3 to 8. Salt solubilisation may be the most appropriate method for the enhanced functionality and utilisation of bambara groundnuts’ protein concentrates.     

喷雾干燥与冷冻干燥鸡蛋粉特性研究

以鲜鸡蛋为原料,利用喷雾干燥和冷冻干燥技术制备鸡蛋粉,对比2种蛋粉水分含量、水分活度、溶解度、色差、微观结构等理化性质,同时检测起泡性、乳化性,并选用喷雾干燥蛋黄粉制备凝胶探讨功能特性。结果表明:喷雾干燥蛋粉和冷冻干燥的蛋粉水分含量、水分活度、溶解度和色差差异显著(P<0.05),且喷雾干燥蛋粉和冷冻干燥蛋粉起泡性及乳化性均在氯化钠浓度为0.5 g/100 mL时达到最大值;制备凝胶最佳条件为加水量为150%、氯化钠浓度为3%、温度100℃、热处理15 min。此项研究将对蛋粉的应用奠定理论基础。     

超声-转谷氨酰胺酶改善红豆蛋白功能性质及结构

采用超声联合转谷氨酰胺酶（transglutaminase,TG）处理红豆分离蛋白（red bean protein isolate,RBPI）,对其功能性质和结构特征进行分析,以探究其结构修饰与功能性质的构效关系。结果表明：超声处理5 min能够使RBPI的乳化活性和发泡能力提高,但会降低泡沫稳定性,对乳液稳定性没有显著影响,同时增加表面疏水性和游离巯基含量;TG能够提高RBPI的乳化活性、乳化稳定性及泡沫稳定性,但会降低发泡能力、表面疏水性和游离巯基含量;超声-TG联合处理的RBPI具有更高的乳化活性和泡沫稳定性,更低的表面疏水性和游离巯基含量,且酰胺Ⅰ带处吸收峰强度增加,更多的无规卷曲结构转变为有序的β-折叠结构,这可能是导致RBPI功能性质改善的原因。超声处理5 min联合TG诱导的蛋白凝胶具有更加均匀、致密的微观结构,且凝胶硬度和黏附力增加,脱水收缩作用降低;峰值温度（Tp）和热焓变（ΔH）显著增加（P＜0.05）,改善了RBPI的热稳定性或三级结构稳定性。以上结果表明RBPI经过超声处理后更利于TG对蛋白质的交联作用,超声-TG联合处理促进了蛋白质功能性质的发挥。     

Production and functional properties of beef lung protein concentrates

This work investigated the production and the properties of meat protein concentrates from beef lungs (BLPC) at pilot scale. Protein recovery and functional properties were compared to those of BLPC obtained using membrane technology in a previous work (Selmane, D., Vial, C., & Djelveh, G. (2008). Extraction of proteins from slaughterhouse by-products: Influence of operating conditions on functional properties. Meat Science, 79, 640–647). An alkaline solubilisation method was applied for protein extraction, followed by pI precipitation for concentration. The physicochemical properties of BLPC such as molecular mass, solubility, surface hydrophobicity, surface tension and interfacial tension, as well as technofunctional emulsifying and foaming properties were determined. These were compared to those of commercial protein ingredients, such as sodium caseinates, whey protein isolates, egg white proteins and soy protein isolates. Results showed that proteins from BLPC included a low-molecular-weight fraction and exhibited good solubility and high hydrophobicity with small surface and interfacial tensions. This explained their excellent emulsifying activity, better than sodium caseinates, and their good foaming properties.     

超声波处理对蜂王浆蛋白功能和结构的影响

探讨不同功率的超声波处理(20 kHz,200、400、600 W)对蜂王浆蛋白溶解性、乳化性、起泡性、水解度以及表面疏水性的影响。同时,通过对王浆蛋白二级结构、三级结构和微观结构的分析,探讨超声波处理改善蜂王浆蛋白功能特性的机制。结果表明,与未处理组相比较,蜂王浆蛋白经过400 W处理后,其溶解度增加10.90%,乳化活性增加67.18%,乳化稳定性增加15.87%,起泡性增加60.00%,起泡稳定性增加118.75%,水解度增加83.33%,表面疏水性增加18.65%。蛋白质的二、三级结构分析显示,该处理条件可以诱导蛋白质发生去折叠化。微观结构分析显示,蛋白质经400 W处理后,其表面较为粗糙,碎片化程度增加。这些结果表明,超声波处理所诱导的蛋白质构象的变化,是其功能特性得以改善的主要原因。     

Properties of protein powder prepared from Cape hake by-products

Cape hake protein powder (HPP) was prepared by alkaline extraction, isoelectric precipitation and freeze drying. It contained 90% protein, 0.53% fat, and 1.44% ash. HPP showed high levels of Na, K, Ca and Mg but lower than in hake mince. The protein profile of HPP was similar to the raw material.The surface hydrophobicity and sulfhydryl group content of HPP were identical to those of the proteins before freeze-drying. The HPP had higher fat absorption capacity, lower emulsifying and foaming capacity than soy protein concentrate, pea protein isolate and egg white powder. The gel strength of HPP was medium (44.8 Nxmm) and was increased by addition of transglutaminase.Gels with different HPP concentrations showed a typical pattern of myofibrillar protein networks with a thermo-reversible behavior. The structure of emulsions prepared with HPP showed increasing complexity as the protein level increased. An increase in the magnitude of the viscoelastic functions and an increment in the magnitude of the zero shear rate limiting viscosity with increasing HPP content were observed.     

Structure and functional properties of rice protein–dextran conjugates prepared by the Maillard reaction

Dextran was grafted on to rice protein (RP) by the wet‐heating Maillard reaction, and the structure and functional properties of the rice protein–dextran conjugates (RPDCs) were investigated. The RPDCs obtained by the Maillard reaction exhibited superior functionality compared with original RP. The solubility, emulsifying activity index, emulsifying stability index, foaming activity index and foaming stability of the RPDCs increased by factors of 7.50, 1.79, 2.20, 1.69 and 2.01, respectively, compared to original RP. The molecular weight, particle size distribution, surface hydrophobicity, secondary structures, amino acid compositions and chemical bonds of RPDCs were also characterised. The structure–function relationship was preliminary discussed, and the relationship suggests that the improvements in the functional properties were closely related to structural changes.     

Relationship between physicochemical and functional properties of amaranth (Amaranthus hypochondriacus) protein isolates

Protein isolates from six amaranth lines/cultivars (APIs) were evaluated to study their physicochemical (hunter colour, protein content and zeta potential), structural (thermal and conformational) and functional (emulsification, foaming, water and fat absorption) properties. APIs had protein content, whiteness index and gel temperature in range of 79.4–85.4%, 41.17–54.26 and 87.8–91.8 °C, respectively. The Fourier‐transform infrared spectra of APIs revealed α‐helix, β‐sheets and random coil conformations in the secondary structure. APIs with higher relative proportion of β‐sheets had higher Differential Scanning Calorimeter denaturation temperature and gel temperature. Minimum protein solubility (PS) was observed at pH 5.0, indicating isoelectric point (pI) of amaranth proteins. The PS, emulsifying activity index (EAI), emulsifying stability index (ESI), foaming capacity (FC) and foam stability (FS) of APIs at neutral pH were related to their zeta potential (ζ). The emulsifying and foaming properties were also determined at different pHs (between 2.0 and 9.0). The EAI‐pH profile of APIs confirmed close relationship between the emulsifying ability and PS.     

核桃蛋白酶解产物的特性研究

研究不同水解度下的核桃蛋白酶解产物的溶解性、乳化性、起泡性、表面疏水性及氮回收率的变化。结果表明：核桃酶解产物溶解度明显增高,均达85% 以上;水解度为9.29% 时乳化性和起泡能力最强;表面疏水性随着水解度的增大而降低;氮回收率随着水解度的增大而升高,水解度为11.76% 时氮回收率可达88.42%。