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.     

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。     

喷射蒸煮处理对米糠蛋白功能特性及体外消化性的影响

研究了喷射蒸煮(HTC)处理对天然米糠蛋白(RBP)与热稳定米糠蛋白(HRBP)提取的影响,并对蛋白的粒度、亚基组成、接枝度、功能性及体外消化性能进行表征。研究表明:HTC处理能显著提高RBP与HRBP的得率(分别从44.9%与14.8%增加到52.2%与44.5%),但对蛋白的纯度没有显著影响。HTC处理后RBP与HRBP的粒度分别从73.6 nm与149.1 nm降低到46.8 nm与96.6 nm,同时生成接枝度28.0%与9.4%的糖基化产物。SDS-PAGE电泳图谱表明,处理后的米糠蛋白生成高分子质量的蛋白聚集体与糖基化产物。HTC处理更有利于HRBP功能性与消化性的提高,且HRBP具有RBP类似的溶解度曲线、起泡能力、泡沫稳定性与良好的乳化能力与消化能力,尽管该处理降低了天然米糠蛋白的消化性。     

超声波辅助热碱法提取藜麦蛋白的工艺优化

以藜麦为原料,NaOH溶液为溶剂,通过超声波辅助热碱法提取藜麦可溶性蛋白,利用单因素实验和响应面试验对影响藜麦蛋白提取率的温度、超声时间、料液比和超声功率进行优化,并测定提取物的溶解度、乳化性和起泡性。结果表明藜麦蛋白的最佳提取条件为温度40 ℃,超声时间2 h,料液比为1∶35 g/mL,超声功率400 W,在该工艺条件下,藜麦蛋白的提取率可达78.20%,与响应面优化试验回归模型的值基本一致。藜麦蛋白的乳化性和起泡性研究表明,3.5%的藜麦蛋白溶液具有较好的溶解性、乳化性和乳化稳定性,溶解度为61.18%,乳化性为5.39 m2/g,乳化稳定性为255.59 min;3%的藜麦蛋白溶液具有较好的起泡性和泡沫稳定性,起泡性为101.0%,泡沫稳定性为66.0%。     

Physicochemical and Functional Properties of Tea Protein

Tea protein has received much attention due to its potential health functions. This article studied the molecular weight, foaming capacity, foam stability, emulsifying capacity, emulsion stability, and oil absorption of tea protein prepared from tea residue by alkali extraction. The results showed that tea protein contained two components with different molecular weights (1.26 × 10⁶ ± 1.3 × 10⁴ and 2.4 × 10⁴ ± 1.1 × 10³). The content of the lower molecular component in tea protein was higher than the higher molecular one. When the concentration of tea protein was 4 mg/mL, its sparkling ability was satisfied, while the foaming capacity and foam stability was the best, respectively, at the conditions of pH 9 and 7. The emulsifying capacity was 62 ± 2% as well as 99 ± 1% of emulsion stability, and oil absorption was 170 ± 7%.     

花生分离蛋白提取工艺优化研究

采用碱提酸沉方法从脱脂花生蛋白粉中提取花生分离蛋白,在单因素试验的基础上,应用响应面法优化花生分离蛋白的提取条件。结果表明：浸提时间和碱液pH 值对提取的花生分离蛋白纯度都有显著影响,且呈非线性关系,最佳提取工艺参数为浸提时间131min、浸提温度50℃、碱液pH10、料液比1:12(g/mL)。在此条件下,花生分离蛋白的纯度为95.05%、提取率71%。响应面法对花生分离蛋白提取条件的优化是可行的。     

Ultrasonic assisted alkali extraction of protein from defatted rice bran and properties of the protein concentrates

Alkaline extraction for the preparation of protein concentrate from rice bran was compared with a range of ultrasonic treatments. Results revealed that the extraction time decreased, and the reaction rate constant increased, with increasing ultrasonic power. The reaction rate constants were 0.0065, 0.0130, 0.0237 and 0.0924 at 40, 60, 80 and 100 W respectively. The defatted rice bran protein concentrate (DRBPC) using ultrasonication (100 W for 5 min) and conventional methods showed no significant difference in bulk densities ( P  > 0.05) but it had higher yield (%) and was lighter brown using ultrasonication ( P  ≤ 0.05). The SEM showed that the residual rice bran after extracting protein using ultrasonication exhibited more damage than the conventional method. The functional properties of both samples were not significantly different ( P  > 0.05) in terms of foam and emulsifying stability. However, the water and oil absorption, foam capacity and emulsion activity were significantly different ( P  ≤ 0.05). The nitrogen solubility index of both DRBPC samples gave similar profiles with the lowest solubility at pH 4–6.     

Characteristics of Isolation and Functionality of Protein from Tomato Pomace Produced with Different Industrial Processing Methods

The seeds separated from tomato pomace may contain valuable protein with unique functional properties. The objectives of this research were to study the impact of industrial hot and cold break tomato processes on protein isolation from defatted tomato seed meal and determine the protein-related functional properties of defatted and non-defatted seed meals. The results showed that the high temperature of hot break process denatured the protein, resulting in the lower protein extraction yield from 9.07 % to 26.29 % for defatted hot break tomato seed (DHTS) compared to from 25.60 % to 32.56 % for defatted cold break tomato seed (DCTS) under various extraction conditions. Hot break process also significantly influenced protein-related functional properties of seed meals. Compared to DCTS, DHTS had higher water absorption capacity (WAC) and oil absorption capacity (OAC) based on the protein weight in the seed meal, but lower emulsifying ability (EA), emulsifying stability (ES), foaming capacity (FC), and foaming stability (FS) based on the whole seed sample weight. When compared to commercial soybean protein isolate (SP), the meals of hot break tomato seed (HTS), DHTS, and DCTS showed higher bulk density and WAC values. The FC and FS of tomato meals were inferior while the ES was superior to SP. High alkaline pH was beneficial to the protein extraction and achieved better EA, ES, FC and FS of all the samples. The results indicated that tomato seed meals have a great potential to be used as functional food ingredients.     

Effect of Partial Proteolysis and Succinylation on Functionality of Corn Germ Protein Isolate

Corn germ protein isolate (CGPI) was partially hydrolyzed with trypsin and pepsin and succinylated at three levels. Various functional and electrophoretic properties of the native and modified protein were determined. Water absorption and foaming properties of CGPI were Improved by partial hydrolysis with trypsin; emulsifying capacity and nitrogen solubility were reduced; oil absorption was increased only slightly. CGPI pepsin hydrolyzate has decreased oil absorption, nitrogen solubility and emulsifying capacity but improved foaming properties; water absorption was unchanged. Treatment of CGPI with succinic anhydride improved water and oil absorption, nitrogen solubility and foaming capacity but decreased emulsifying capacity; foam stability was unchanged. Succinylation retarded electropohoretic mobility while hydrolysis altered band intensities.     

Functional Properties of Pork Liver Protein Fractions

The functional (emulsifying, gelling and foaming) properties of liver protein fractions as well as their molecular weight distribution and surface hydrophobicity were investigated and compared to commercial proteins. Two protein fractions were characterized: water soluble (WSLP) and WSLP combined with salt soluble liver proteins (W?+?SSLP). The effect of salt concentrations was also investigated (0, 1.8 and 3.4 % NaCl). Both WSLP and W?+?SSLP displayed good emulsifying properties and foam stability. However, their gelling properties were rather poor. An increase in salt concentration decreased the emulsifying properties of WSLP while the effect on W?+?SSLP was less pronounced. Addition of 1.8 % NaCl increased foaming ability of WSLP and W?+?SSLP while foam stability was not affected. Further increase of NaCl (3.4 %) decreased both foaming ability and foam stability and is probably attributed to refolding of the protein molecules because of the higher level of hydrophobic groups with 3.4 % NaCl. Gel forming ability of WSLP and W?+?SSLP containing 0 % was higher compared to high salt concentrations. However, higher salt concentrations shifted onset gelation temperature of WSLP and W?+?SSLP to lower temperatures probably due to partial unfolding of the proteins as indicated by an increase of the surface hydrophobicity.     

低温花生粕蛋白制备及其饮料稳定性分析

以低温花生粕为原料,利用碱溶酸沉法提取花生分离蛋白,继而制备花生蛋白饮料,考察自制花生蛋白饮料的稳定性,并研究其氮溶指数、乳化活性及乳化稳定性等功能特性。结果表明,最佳工艺条件为pH 9.5、碱提温度55℃、料液比1∶11(g/mL)、提取时间2.5 h,此条件下花生分离蛋白提取率可达90.25%。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析显示,其中包含花生蛋白所有特征条带。花生蛋白饮料的平均粒径(D[4,3])为4.31μm,稳定性分析仪测出粒子动态变化斜率(Slope)值为26.66%/h。低温花生粕制备的花生蛋白饮料具有良好的稳定性,这为花生粕高值化利用提供了新方向。     

不同方法提取苜蓿叶蛋白效果的比较及表征

分别采用酸热法、碱化法和发酵法3种方法制备苜蓿叶蛋白,通过优化制备工艺并比较叶蛋白得率、氮含量、溶解性、起泡性与泡沫稳定性、乳化性及乳化稳定性、持水性、吸油性等功能性质,并进行电镜观察表征。结果表明,发酵法制备苜蓿叶蛋白的得率和氮含量最高分别为14.9%和45.08%,明显高于酸化法和碱化法;比较其功能性质,碱化法制备的苜蓿叶蛋白在起泡性、持水性和吸油性上优于其他两种方法,分别为200.00%、5.40%和5.31%;发酵法制备的苜蓿叶蛋白溶解性、乳化性及乳化稳定性较好,分别为80.52%、78.60%和20.65%。扫描电镜观察3种方法所制备苜蓿叶蛋白的表面结构,碱化法制备的苜蓿叶蛋白结构疏松,且有一定程度的破坏,酸化法和发酵法的苜蓿叶蛋白表面结构紧密、连续完整,并发现发酵法还具有一定的降解效果。说明利用不同的方法制备苜蓿叶蛋白,其得率、氮含量、功能性质及表面结构有较大差异。     

Physicochemical Properties and Functionality of Rice Bran Protein Hydrolyzate Prepared from Heat-stabilized Defatted Rice Bran with the Aid of Enzymes

ABSTRACT: Molecular size, thermal properties, hydrophobicity, nitrogen solubility, and emulsifying and foaming properties were determined for protein products from heat‐stabilized defatted rice bran. The freeze‐dried and spray‐dried proteins had molecular sizes between 6.5 to 66.2 kDa; denaturation temperatures of 84.1 and 84.6 °C, enthalpies of 2.5 and 2.37 J/g, hydrophobicities of 20677 and 22611, maximum solubilities of 66.3% and 66.1% at pH 12.0, emulsifying capacities of 0.19 and 0.18, emulsion stabilities of 16.5 and 17.3 min, foam capacities of 4.0 mL and 4.2 mL, and negligible foam stabilities. These results demonstrated that the extracted rice bran protein has potential as a nutraceutical ingredient in food applications.     

不同种类活性短肽的理化与功能特性比较

比较了大米肽、大豆肽、小麦肽、白蛋白肽、花生肽、山药肽、玉米肽、海洋胶原蛋白肽和乳清肽在不同p H值和钠离子强度条件下的乳化活性、乳化稳定性、溶解性、起泡性及泡沫稳定性。结果表明:碱性条件下各活性短肽的乳化活性、乳化稳定性、溶解性、起泡性均优于酸性条件下的,但其泡沫稳定性差异不明显;随着钠离子强度的增强,各活性短肽的起泡性增强,乳化活性、乳化稳定性及溶解性降低,但其泡沫稳定性变化不明显;在相同p H值条件下,乳清肽、玉米肽、大豆肽和花生肽的乳化活性、乳化稳定性、起泡性及泡沫稳定性优于大米肽、小麦肽、白蛋白肽、山药肽和海洋胶原蛋白肽;在相同的钠离子强度条件下,乳清肽、玉米肽、大豆肽、海洋胶原蛋白肽和花生肽的乳化稳定性优于大米肽、小麦肽、白蛋白肽和山药肽,乳清肽和大豆肽的乳化活性、起泡性和泡沫稳定性优于其他7种短肽。不同种类活性短肽上述理化特性差异与其氨基酸组成和分子质量大小密切相关,应根据其特性差异进行选择性应用。     

Functional and bioactive properties of Velvet bean (Mucuna pruriens) protein hydrolysates produced by enzymatic treatments

Velvet bean (Mucuna pruriens) protein hydrolysates were produced with gastrointestinal enzymes. Functional properties such as nitrogen solubility, emulsifying capacity and emulsion stability, foam capacity and stability of the hydrolysates were determined. Angiotensin I-converting enzyme inhibitory, antioxidant and antithrombotic capacities were evaluated to determine the biological activity of hydrolysates. For pepsin, degree of hydrolysis (DH) increased sharply between 5 min (22.33 %) and 60 min (28.07 %), respectively, with a maximum DH of 33.50 % (90 min). For pancreatin, DH increased sharply between 5 min (25.08 %) and 90 min (34.92 %), respectively, with a maximum DH of 37.23 % (120 min). For sequential system pepsin–pancreatin, DH increased sharply between 5 min (25.21 %) and 60 min (32.82 %), respectively, with a maximum DH of 34.14 % (120 min). Hydrolysates with the lowest DH and the highest DH were selected to assess the functional and biological potential. Mucuna pruriens limited hydrolysates can be considered a useful food additives to provide functional properties, while M. pruriens extensive hydrolysates can be used as nutraceutical ingredients.     

马铃薯蛋白组分的分离提取和功能性质研究

采用透析与等电点沉淀相结合的工艺方法提取分离马铃薯块茎蛋白组分;并对其理化性质和功能性质进行检测。结果显示：此提取工艺流程合理易行,马铃薯块茎酸性蛋白组分和碱性蛋白组分的得率分别为0 .535%、0.741%;纯度分别为92.5%、89.2%;酸性蛋白组分沉降系数5S,分子质量82kD;碱性性蛋白组分沉降系数8S,分子质量140kD。SDS-PAGE 电泳图谱表明5S 蛋白组分有1 条亚基带;8S 蛋白组分有4 条亚基带。5S 蛋白组分的表面疏水性、吸油能力、乳化性显著高于8S 蛋白组分;而8S 蛋白组分的总巯基含量以及起泡性高于5S 蛋白组分。马铃薯蛋白组分可以作为功能食品的蛋白添加原料。     

Comparison of the effect of hydrodynamic and acoustic cavitations on functional,rheological and structural properties of egg white proteins

The impacts of hydrodynamic cavitation (HC) (orifice plate-2 mm) and acoustic cavitation/ultrasound (US) (probe sonicator- 50% amplitude; 20 kHz frequency) on the functional (foaming, gelling, emulsifying), physicochemical (solubility), rheological and structural properties of egg white proteins (EWP) were evaluated. The egg white solutions were treated for 5, 10 and 15 min for both HC and US. The results suggested that HC-treated samples had higher impact on physiochemical and functional properties when compared to US-treated samples. The best foaming, emulsifying and gelling property was obtained for HC-treated samples (15 min treatment time). Both cavitation treatments exhibited shear thinning behavior, among which US-treated samples had the lowest viscosity. HC-treatment applied for 15 min provided the highest in vitro digestibility (75.51 ± 0.126%) among all the samples. The FTIR spectra of EWP exhibited similar backbone structure for all the samples, while the secondary structure obtained from deconvolution of Amide-I peak differed significantly. Moreover, for product development with EWP, HC -treated samples were more appropriate in gelling and emulsifying applications, which can ensure quality products with higher in vitro digestibility. Overall, this study indicated that HC treatment (for 15 min) improved the functional, rheological, and structural properties of EWP.     

Preparation and Functional Properties of Linseed Protein Products Containing Differing Levels of Mucilage

The functionality of two high-mucilage protein concentrates (HMPC) prepared from linseed and linseed expeller cake by extracting and coprecipitating the mucilage with protein was compared with those of a low-mucilage flour (LMF), a protein concentrate (LMPC), and a protein isolate (LMPI) in simple systems. The HMPC samples had better water absorption and emulsifying properties, higher foaming capacity, but lower nitrogen solubility, oil absorption, and foam stability than LMF and LMPC. They also registered higher values of viscosity and emulsification characteristics than LMPI.     

花生湿热处理对其分离蛋白的结构和功能特性的影响

本文通过还原/非还原电泳、热差示扫描、表面疏水性及等电点测定等手段,表征了花生湿热处理对其分离蛋白结构和功能特性的影响.结果表明:在105℃随着湿热处理时间延长其分离蛋白中伴球蛋白所占比例逐渐减少,球蛋白在加热75min后产生热聚集,此外通过美拉德反应生成的糖蛋白含量逐渐增加,分离蛋白等电点向酸性偏移,表面疏水性先逐渐...     

Functional Characteristics of Protein Flaxseed Concentrate Obtained Applying a Response Surface Methodology

ABSTRACT:  Food preferences by human beings are based on sensory attributes such as texture, flavor, color, and appearance that depend mainly on the interactions between minor and major components of the food. Some functional properties depend directly on the proteins, such as oil and water absorptions, foam and emulsion activities, and viscosity. The objective of this work was to obtain and evaluate the functional properties of flaxseed protein concentrate. Flaxseed was ground, defatted, and sieved to eliminate hull fiber. Surface response methodology with 5 central points and 4 axial points was used to determine how to obtain the highest protein concentrate. The independent variables used were solubilization pH (which varied from 9 to 11) and precipitation pH (which varied from 4.2 to 4.8). Treatment with a solubilization pH of 11 and a pH extraction of 4.8 gave 66.03% protein content. The flaxseed protein concentrate contained 2.56% fat, 6.62% ash, 2.44% insoluble fiber, 15.79% soluble fiber, and 6.59% sugars. The product had oil and water absorption capacities of 150.25% and 253.5%, respectively. Better foam stability (83.33%), emulsifying capacity (84.76 mL/g), and emulsifying activity (88.37%) of the flaxseed protein concentrate were observed at a pH 6. In light of its functional properties as indicated by this study, flaxseed protein concentrate may be recommended for use as an ingredient in products such as meat batters, hamburgers, and ice cream.