超声辅助水酶法同时制备油茶籽油及水解蛋白的响应面优化

以油茶籽为原料,在水酶法的基础上结合超声波辅助技术提取油茶籽油和蛋白。在单因素的基础上,选出最优的超声处理条件:超声温度45℃,超声时间30 min,超声功率300W,料液比1:5。然后采用响应面分析试验确定的最佳工艺为:加酶量1.3%,酶解p H8,反应温度60℃,酶解时间3.5 h。在最佳工艺条件下,油茶籽油提取率为89.42%,油茶籽蛋白提取率为89.86%。     

超声辅助酶法提取燕麦蛋白的研究

采用超声波辅助酶法从燕麦粉中提取燕麦蛋白,研究了料水比、粉碎度、超声时间、超声功率、超声温度以及酶解pH值、酶解时间、酶解温度、加酶量对燕麦蛋白提取率的影响.通过单因素实验和正交实验得到最佳提取条件,即料水比1: 8、粉碎度40目、超声时间25 min、超声功率40 W、超声温度50℃、加酶量1.1%(中性蛋白酶)、酶解pH8、酶解时间1.5 h、酶解温度45℃,此条件下燕麦蛋白的提取率可达80.3%.     

水酶法提取榛子蛋白工艺优化

以榛子仁为原料,利用Alcalase碱性蛋白酶水解,进而提取榛子蛋白。以榛子仁总蛋白提取率为指标,对影响因素进行研究。在单因素试验的基础上采用响应面法优化工艺条件,得到最佳酶解条件：加酶量2.0%、温度55℃、酶解时间2.5h、料水比1:5(g/mL)、pH8.9。由F检验可得因素贡献率为x1＞x2＞x4＞x5＞x3,即加酶量＞酶解温度＞料液比＞酶解pH值＞酶解时间。     

响应面优化超声波辅助水酶法提取花生蛋白工艺

采用水酶法结合超声波预处理提取花生蛋白,在单因素实验基础上,选出最优的超声时间和超声温度,重点以酶用量、酶解pH、酶解温度、酶解时间和料液比为考察的影响因子,花生蛋白提取率为响应值。确定最优复合酶水解的水酶法提取花生蛋白工艺条件为：加酶量为1.59%,温度为56.5℃,酶解时间为3.9h,料水比为1∶4.4,pH为9.0,此时蛋白提取率为94.31%±0.37%。     

响应面法优化水酶法提取松子蛋白的研究

主要研究了水酶法提取松子蛋白的酶解工艺。选用Alcalase碱性蛋白酶作为水解酶,以总蛋白提取率为指标。通过单因素实验和响应面实验,得到影响实验的因素依次为加酶量>酶解温度>料液比>酶解pH>酶解时间。确定最佳的酶解参数为:加酶量1.9%,温度55℃,酶解时间2.2h,料液比1∶5,pH8.8,此时总蛋白提取率为87.92%。     

薏仁米糠蛋白酶法提取工艺的优化

为了研究酶法提取薏仁米糠蛋白的最佳工艺,在单因素试验的基础上,采用Box-Benhnken试验设计,利用响应面法优化薏仁米糠蛋白的提取条件。分析回归方程确定薏仁米糠蛋白提取率的影响因子,确定最佳提取工艺为料液比1∶29（g∶mL）,酶解温度50 ℃,酶解时间1.5 h,酶解pH 9.8。在此最佳提取工艺条件下,薏仁米糠蛋白平均提取率79.66%,产品纯度为73.42%。     

酶法提取红松种子蛋白工艺的研究

以红松种子为原料,利用中心组合试验设计对影响红松种子蛋白提取的因素水平进行了综合考察,优化了红松种子蛋白的提取工艺参数.采用单因素试验设计,考察了酶解pH、固液比、提取温度、提取时间、加酶量等因素对红松种子蛋白提取率的影响,通过对单因素试验结果的分析,筛选出影响蛋白质提取率的关键性因素.结合所筛选的关键因素应用响应面分析法研究了提取液pH、提取温度、提取时间、加酶量等关键因素对蛋白质提取率的影响,采用回归分析技术、拟合二次多项式试验模型,应用模糊数学处理优化,得到了最佳的综合因素水平,分别为:固液比1:25;pH 8.4;提取时间3.07 h;加酶量1.53%;提取温度54.16℃,在最佳条件下红松种子蛋白的提取率预测值为88.29%,实际测定值88.06%.结果表明采用响应面法来寻求酶法提取红松种子蛋白最佳条件是可行的.     

榛子蛋白提取及纯化的工艺优化

摘要：以榛子粕为原料,采用碱性蛋白酶酶解辅助碱溶酸沉法提取榛子蛋白,然后加入碱液复溶、碱性蛋白酶酶解、酸沉纯化。在单因素试验的基础上采用响应面法对提取过程中酶解工艺条件进行优化,采用正交试验优化榛子蛋白纯化工艺。结果表明：最优酶解工艺条件为酶解温度46 ℃、pH 8、酶解时间3.7 h,在此条件下榛子蛋白提取率达到53.16%;最佳纯化条件为反应温度50 ℃、液料比5∶ 1、复溶pH 11,在此条件下榛子蛋白纯度为95.23%。     

水酶法提取青稞蛋白工艺研究

以纤维素酶作为水解酶,采用水酶法从青稞米籽粒中提取蛋白质。通过单因素实验和正交实验,得到提取青稞蛋白的最佳条件,即料/水比1:5、加酶量0·2%、酶解时间14h、酶解温度45℃、酶解pH6·5。在最佳条件下青稞蛋白的提取率为69·3%。     

水酶法从冷榨油茶籽饼中提取油和蛋白的工艺研究

利用响应面法对水酶法从冷榨油茶籽饼中提取油和蛋白的工艺进行优化。在单因素实验基础上,以酶添加量、温度、pH值、时间为影响因素,油和蛋白提取率为响应值,应用Box-Behnken实验设计建立数学模型,进行响应面分析。结果显示,拟合得到的方程显著,可以用以预测不同条件下油与蛋白质的提取率。水酶法提取冷榨油茶籽饼中的油及蛋白质的最优工艺条件为:料液比1:5、酶添加量1.6%、pH 8、温度60℃、时间4.5 h,在此条件下,油脂及蛋白质提取率分别为81.42%、79.36%。     

Improvement of the nutritive value of cereals by leaf protein supplementation

The gross composition and amino acid content of the proteins of barley, corn, rye and wheat grains were determined. Leaf protein concentrates (LPC) were produced from the green matter of clover, lucerne, barley and ryegrass using standard methods and analysed as for the cereal grains. Each cereal was mixed with each concentrate at a protein ratio of 2:1, respectively. The chemical score (CS) and essential amino acid index (EAAI) of the cereals, the protein concentrates and their mixtures were calculated. The biological value (BV) and true digestibility (TD) of all proteins were determined on rats using the Thomas-Mitchell balance method. LPC proteins contained more lysine (4.6–6.0%) but less cystine than cereal proteins (2.8–3.8 and 2.3–2.7 g per 16 g N, respectively). The CS and BV of LPC proteins were low (30–40 and 44–58, respectively) because of the low cystine content. Mixing cereals with LPC improved the CS, EAAI and BV of their proteins. The BV of the protein mixtures was in almost every case higher than that of either protein alone, but the digestibility of the cereal proteins was reduced as a result of admixture with LPC, especially with clover LPC.     

过氧自由基氧化对大米蛋白结构的影响

采用不同浓度2,2’-盐酸脒基丙烷(AAPH)在有氧条件下热分解产生的过氧自由基代表脂质氧化过程中的脂质自由基,研究过氧自由基氧化对大米蛋白结构的影响。结果表明,当AAPH浓度从0增加至25 mmol/L,大米蛋白羰基和二硫键含量分别由3.77和13.88 nmol/mg增加至7.26和15.73 nmol/mg,游离巯基由7.32 nmol/mg下降至1.97 nmol/mg,表明过氧自由基诱使大米蛋白发生了氧化;傅里叶红外分析表明蛋白质氧化导致大米蛋白α-螺旋和β-折叠含量下降,β-转角和无规卷曲含量上升。随着大米蛋白氧化程度的增加,大米蛋白粒径从126 nm增加到216 nm,表面疏水性从1053下降到568,内源荧光最大荧光峰位蓝移,内源荧光强度下降,并且在分子量分布图中高分子量聚集体含量逐渐增加。表明过氧自由基氧化修饰导致大米蛋白结构改变和形成氧化聚集体。     

Structural modification of soy protein by the lipid peroxidation product malondialdehyde

BACKGROUND: Protein oxidation results in covalent modification of structure and deterioration of functional properties of target protein. Oxidation extent of soy protein was affected by the content and type of lipid peroxidation (LPO) products in defatted soybean flours during storage and processing. Malondialdehyde (MDA) was selected as a secondary byproduct of LPO to investigate the effects of oxidative modification of LPO‐derived reactive aldehyde on soy protein structure. RESULTS: MDA reacted with ε‐amino and sulfhydryl groups of soy protein, and resulted in an increase in protein carbonyl groups but a decrease in sulfhydryl/disulfide, free amines and lysine. The decrease in solubility, surface hydrophobicity and intrinsic fluorescence indirectly indicated that MDA induced soy protein aggregation, and results of high‐performance size‐exclusion chromatography directly showed that gradual aggregation of soy protein was induced by increasing concentration of MDA. Results of electrophoresis indicated that MDA caused soy protein aggregation, and non‐disulfide covalent bonds were involved in aggregate formation. CONCLUSION: The results showed that sensitivity of soy protein was related to MDA concentration. Soy protein gradually aggregated with increase of MDA concentration; β‐conglycinin was more sensitive to MDA modification than glycinin. Copyright © 2009 Society of Chemical Industry     

Improvement of the solubility and emulsification of rice protein isolate by the pH shift treatment

In the current research, we have adopted a pH shift treatment method that can significantly improve the solubility and emulsification of rice protein isolate (RPI) under neutral conditions. Our results showed that the RPI reached a quasi-equilibrium state at 1 h after alkali shift treatment, and the solubility and emulsifying properties of RPI were significantly improved compared with the control. In addition, the particle size of RPI decreased considerably under the alkali shift treatment. The results of electron microscopy showed that the RPI aggregates were depolymerised and the particle size distribution was more uniform. The pH shift treatment induced the rearrangement of protein secondary structure, and the exposure of hydrophobic groups increase the surface hydrophobicity of RPI. The change in endogenous fluorescence spectrum, UV and the disulfide bond content all showed that the conformation of RPI changed significantly through pH shift treatment. In addition, it was found that the RPI treated under pH 10–11 shift possessed the best property to stabilise the emulsion. This study showed that under the condition of pH10 and pH11 shift treatment, the structural and functional properties of RPI were vastly improved, and the application of RPI in food was greatly ameliorated.     

高蛋白质面粉提取技术的研究

首先对高蛋白质面粉提取设备-面粉气流分级机的结构和工作原理做了简要的介绍。使用中试实验设备,分析了不同转速和风量下面粉分级提取的效果,并在生产中进行了现场生产技术指标的测定。结果表明,气流分级技术能够有效地解决面粉生产中高蛋白质面粉的提取问题,为高筋粉的生产提供了一条有效的途经。     

Flavourzyme酶水解蛋清蛋白的工艺研究

以水解度和蛋白质残留量为指标,研究温度、pH、酶用量及蛋清浓度对Flavourzyme酶解蛋清蛋白的影响,并通过正交试验来确定其最佳工艺。结果是温度55℃、pH6.5、加酶量为质量分数6%、蛋清料液质量体积比1 g:5 m L为最佳工艺参数。在该条件下,6 h酶解物的蛋白质残留率为27.68%,水解度为38.75%,水解物的相对分子质量大部分集中在300以下,即主要以游离氨基酸及二肽形式存在。     

Model salad dressing emulsion stability as affected by the type of the lupin seed protein isolate

Model salad dressing emulsions of an oil volume fraction of 0.50 were prepared using two types of lupin seed protein isolate (LSPI) differing in the method applied for their isolation and their protein composition. The dressing stability against creaming and droplet coalescence were studied and correlated with data on oil droplet size, rheological characteristics and the amount of protein adsorption at the droplet surfaces. Model salad dressing emulsions containing the isolate, mainly composed of lupin globulins, exhibited higher stability and more pronounced rheological characteristics compared to those prepared with the isolate enriched in albumins or with the mixture of the two isolates. The lupin albumins appeared to displace the globulins from the droplet surfaces, following competitive adsorption from mixtures of the two types of the lupin isolates. The results are discussed in terms of droplet interaction and rearrangement as they are influenced by the presence of the adsorbed protein molecules and aggregates which appear to determine long‐term stability of the emulsion systems. Copyright © 2006 Society of Chemical Industry     

Comparison of the Precipitation of Alfalfa Leaf Protein and Bovine Serum Albumin by Tannins in the Radial Diffusion Method

The precipitation of protein by condensed and hydrolysable tannins was evaluated with the radial diffusion method of Hagerman (1987) using bovine serum albumin (BSA) and isolated leaf protein from fresh alfalfa (Medicago sativa). Alfalfa leaf protein (AALP) was included at two concentrations, 25 and 156 mg N litre^-1, at pH 6·8 and 39°C to simulate rumen conditions. The condensed tannins were purified from lyophilised samples of Arachis pintoi, Desmodium ovalifolium, Gliricidia sepium, Manihot esculenta and quebracho (Schinopsis balansae). Hydrolysable tannins from tannic acid (TA) were used as well. There was a significant interaction (P<0·001) between tannin and protein source, and protein level on protein precipitation. Most purified condensed tannins (CTs) precipitated more AALP than BSA when protein was included at the same level. Purified CT from quebracho and hydrolysable tannin from TA failed to precipitate AALP at both protein levels. In a second experiment, tannins from crude plant extracts were studied in the radial diffusion method using BSA and two levels of AALP. The crude plant extracts were obtained from lyophilised plant samples of A pintoi, Centrosema macrocarpum, Clitoria ternatea, D ovalifolium, Erythrina berteroana, E poepigiana, G sepium, M esculenta, Pueraria montana and P phaseoloides. The protein precipitated by soluble tannins in the plant samples was correlated to the total phenolic content and to the soluble CT estimated by the acid butanol assay or by the radial diffusion method. Tannins from different plant species precipitated different amounts of BSA and AALP. Therefore, the measures of the biological activity of tannins based on BSA precipitation may not reflect the ability of tannins to precipitate proteins of plant origin such as those commonly found in the diets of herbivores. The present study offers the possibility of using the radial diffusion method with plant proteins at precipitation conditions similar to those in the rumen. © 1997 SCI.     

丙二醛氧化对米糠蛋白结构及功能性质的影响

选取丙二醛（malondialdehyde,MDA）代表脂质过氧化反应中的活性次生氧化产物,借助蛋白质化学理论和谱学分析技术等手段,研究脂质过氧化产物对米糠蛋白结构和功能性质以及构效关系的影响。结果表明,米糠蛋白羰基含量随MDA氧化诱导浓度的增加而增大,而游离氨基含量逐渐减少。米糠蛋白α-螺旋和β-折叠含量随MDA氧化诱导浓度增加逐渐增大,β-转角结构和无规卷曲结构随之呈现逐渐降低的变化趋势。MDA氧化诱导的米糠蛋白色氨酸荧光λmax逐渐蓝移。低氧化诱导浓度下MDA对米糠蛋白亚基组成无显著影响,随着MDA氧化诱导浓度增加,分子质量为53、49、36、21、14 kDa的亚基归属条带均有所变浅,条带逐渐变窄,并且分子质量为36、21、14 kDa的亚基逐渐消失。随着MDA氧化诱导浓度的增大,米糠蛋白粒径、多分散指数、浊度及泡沫稳定性均随之逐渐增大,而氧化米糠蛋白溶解度、表面疏水性、乳化性、乳化稳定性和起泡性逐渐降低。     

Influence of Xanthan Gum on the Structural Characteristics of Myofibrillar Proteins Treated by High Pressure

The effects of xanthan gum on the structural modifications of myofibrillar proteins (0.3 M NaCl, pH 6) induced by high pressure (200, 400, and 600 MPa, 6 min) were investigated. The changes in the secondary and tertiary structures of myofibrillar proteins were analyzed by circular dichroism. The protein denaturation was also evaluated by differential scanning calorimetry. Likewise, the protein surface hydrophobicity and the solubility of myofibrillar proteins were measured. High pressure (600 MPa) induced the loss of α‐helix structures and an increase of β‐sheet structures. However, the presence of xanthan gum hindered the former mechanism of protein denaturation by high pressure. In fact, changes in the secondary (600 MPa) and the tertiary structure fingerprint of high‐pressure‐treated myofibrillar proteins (400 to 600 MPa) were observed in the presence of xanthan gum. These modifications were confirmed by the thermal analysis, the thermal transitions of high‐pressure (400 to 600 MPa)‐treated myofibrillar proteins were modified in systems containing xanthan gum. As consequence, the high‐pressure‐treated myofibrillar proteins with xanthan gum showed increased solubility from 400 MPa, in contrast to high‐pressure treatment (600 MPa) without xanthan gum. Moreover, the surface hydrophobicity of high‐pressure‐treated myofibrillar proteins was enhanced in the presence of xanthan gum. These effects could be due to the unfolding of myofibrillar proteins at high‐pressure levels, which exposed sites that most likely interacted with the anionic polysaccharide. This study suggests that the role of food additives could be considered for the development of meat products produced by high‐pressure processing.