高静压处理对花生蛋白的改性研究

研究高静压(300 MPa～600 MPa)处理对花生分离蛋白、花生球蛋白的溶解性、乳化性(EAI)、乳化稳定性(ESI)、表面疏水性、巯基含量等性质的影响,并对各功能性质的相互关联性进行了分析。结果表明:高静压处理可有效的改善花生分离蛋白和花生球蛋白的溶解性和乳化性,但是会降低其乳化稳定性。在400 MPa,花生分离蛋白具有最大的乳化性和表面疏水性,花生球蛋白具有最大的溶解性。在500 MPa,花生球蛋白具有最大的乳化性和表面疏水性,花生分离蛋白具有最大的溶解性;随着压力的升高,花生球蛋白和花生分离蛋白的游离巯基含量呈下降趋势。表面疏水性与乳化性存在一定的正相关。结果表明,高静压处理可以有效改善花生蛋白的功能性质。     

乙酰化改性对米渣蛋白功能性质的影响

采用乙酰化对米渣蛋白进行改性,研究了米渣蛋白在乙酰化改性过程中巯基和二硫键含量、表面疏水性、溶解性以及乳化性的变化。结果表明,随改性程度的增加,米渣蛋白中暴露巯基含量逐渐增加,总游离巯基含量逐渐下降,二硫键含量逐渐增加,表面疏水性先下降后升高。乙酰化改性后的米渣蛋白在p H5~10范围内的溶解性、乳化活性和乳化稳定性明显增加,但是p H2~4范围内的溶解性和乳化活性却有所降低。可见,乙酰化改性能改善米渣蛋白的部分功能性质。     

水力空化对不同热处理后大豆球蛋白理化和乳化性质的影响

利用水力空化处理不同热处理后的大豆球蛋白,通过比较处理前后大豆球蛋白内源荧光光谱、表面疏水性、暴露巯基含量、二硫键含量、溶解性和乳化性的变化,研究水力空化对大豆球蛋白理化性质和乳化特性的影响。结果表明:经水力空化处理后,所有样品的内源荧光光谱最大吸收峰蓝移,暴露巯基含量、二硫键含量和溶解性均减小,乳化稳定性增加,而对乳化活性和表面疏水性的影响与大豆球蛋白热处理温度有关,70℃热处理的蛋白表面疏水性和乳化活性增加,80℃和90℃热处理的蛋白则表现相反的变化趋势。由此可见,水力空化处理可以使大豆球蛋白的理化性质发生变化,在一定条件下可以改善大豆球蛋白的乳化稳定性,且改善程度与蛋白初始状态有关。     

限制性酶解燕麦蛋白功能特性和抗氧化活性

利用碱性蛋白酶限制性酶解燕麦蛋白,研究了不同水解度(DH)酶解物的溶解性、乳化性、乳化稳定性及对DPPH自由基清除率。试验结果表明,限制性酶解后燕麦蛋白的功能性质有了很大提高。水解初期,随着DH增加,溶解性增大,当DH为15%, pH 8时,溶解度达到79.78%,比原料蛋白在此pH下的溶解性提高了163.91%。乳化性随DH增加而降低,当DH为5%, pH 8时,乳化性达到0.852,比原料蛋白在此pH下的乳化性提高了56.04%。乳化稳定性的变化规律与乳化活性相反,当DH为20%, pH 8时,乳化稳定性达到73.14%,比原料蛋白在此pH下的乳化性提高了59.76%。酶解物对DPPH自由基清除率随着DH增加而变大, DH 5%、DH 10%、DH 15%和DH 20%酶解物对DPPH自由基清除率的IC_(50)分别为6.274, 6.145, 6.050和5.640 mg·mL~(-1),而且浓度与清除率呈现出明显的剂量效应。     

限制性酶解米糠蛋白功能性质研究

为提高米糠蛋白的功能性质,同时避免米糠蛋白的结构破坏和苦味肽的大量产生,对米糠蛋白进行限制性酶解改性,对碱性蛋白酶限制作用下的米糠蛋白酶解物的功能性质进行研究。以米糠蛋白的溶解性,起泡性及起泡稳定性,乳化性及乳化稳定性为考察指标,分析不同水解度下米糠蛋白的功能性质。结果表明:米糠蛋白进行限制性酶解后功能性质有了很大提高,限制酶解下米糠蛋白的溶解性在DH 14,p H 10下达到98.48%,比原料蛋白在此p H下的溶解性提高了24.86%;起泡性在DH 8,p H 12下达到最大值175 m L,比原料蛋白在此p H下的起泡性提高了121.52%;起泡稳定性在DH 4,p H 2下达到最大值82.76%,比原料蛋白在此p H下的起泡稳定性提高了7.14%;乳化活性在DH 4,p H 12下达到最大值0.739,比原料蛋白在此p H下的乳化活性提高了9.32%;乳化稳定性DH 8,p H 8下达到最大值57.5%,比原料蛋白在此p H下的乳化稳定性提高了20.15%;米糠蛋白经过限制性酶解后功能性质较原料蛋白均有很大提高。     

红衣组分对花生分离蛋白及其酶解产物理化和抗氧化性质的影响

以花生为原料,研究了花生红衣组分对花生分离蛋白及其酶解产物理化和抗氧化性质的影响。研究结果表明:含红衣的分离蛋白酶解速度低于不含红衣的;相同水解度条件下,含红衣的表面疏水性小于脱红衣的;GPC分布中,含红衣的峰值大于脱红衣的;红衣组分能够提高花生分离蛋白及其酶解产物的溶解性、乳化稳定性、乳化活性;在相同水解度条件下,含红衣的水解产物多酚含量显著高于脱红衣的,多酚含量的差异与花生分离蛋白及其水解产物的抗氧化性具有正相关性。     

限制性酶解对亚麻籽蛋白功能特性、结构的影响及其在冰淇淋中的应用

本文研究了限制性酶解对亚麻籽蛋白功能特性及结构的影响,进一步研究了其在冰淇淋中的应用。结果表明,限制性酶解能显著提高亚麻籽蛋白的溶解性,酶解时间越长溶解性越好;但对亚麻籽蛋白的乳化性及乳化稳定性、起泡性及泡沫稳定性、持油性来说需要适度的水解,限制性酶解时间为5min时乳化稳定性、泡沫稳定性、持油性达到最高,限制性酶解时间为10min时乳化性和起泡性达到最高;但限制性酶解会削弱亚麻籽蛋白的持水能力。同时发现亚麻籽蛋白经限制性酶解后粒径较小的分子增多,平均粒径降低;表面巯基含量及表面疏水值均呈先增加后降低趋势,表明适度的限制性水解使其结构展开暴露出先前埋在蛋白质内部的巯基及疏水基团;圆二色谱分析结果显示,经限制性酶解其α-螺旋和无规则卷曲的含量增加,β-折叠和β-转角的含量下降,表明其二级结构发生改变更具柔韧性;扫描电镜分析结果发现经限制性酶解由较大平滑片状变成了较小松散碎片状。添加限制性酶解亚麻籽蛋白制作冰淇淋,随着其添加量的增加感官品质先上升后下降,添加量为4%时感官评分值达最高为85.0分,同时还发现随着添加量的增加其膨胀率显著上升、融化率显著下降、融化后其大气泡数量呈增加趋势,表明添加4%的限制性酶解亚麻籽蛋白可获得品质较好的冰淇淋。以上结果表明限制性酶解改变了亚麻籽蛋白结构,使其具有较好的功能特性,可添加在冰淇淋中。     

鳙鱼鱼肉蛋白的酶解及其对功能性质的影响

为了改善鳙鱼鱼肉蛋白(BCMP)的功能性质以扩大其在食品工业中的应用,以鳙鱼为原料制备了鳙鱼鱼肉蛋白,并利用碱性蛋白酶Alcalase2.4L对其进行水解,得到了3种不同水解度(DH4.5%、DH9.0%、DH13.5%)的酶解物。研究了BCMP及其酶解物的功能性质,包括溶解性、持水性、持油性、乳化性、起泡性。结果表明,与原鳙鱼鱼肉蛋白相比,酶解物的功能性质除持油性以外均有不同程度的提高。此外,DH4.5%的酶解物乳化性和起泡性最高,过度水解(DH9.0%、DH13.5%)反而造成乳化性和起泡性下降。     

鸡蛋清蛋白水解物的物化及功能性质的研究

蛋清蛋白质溶解性欠佳且容易起泡,使其应用受限。本文利用Alcalase酶解鸡蛋蛋清蛋白制取水解度为5~15%的酶解物并对酶解物的理化性质和功能性质进行了表征。测定性质包括乳化性、起泡性及稳定性以及溶解性、表面疏水性。所有酶解产物具有较低的表面疏水性,水解大大提高了溶解度,当水解度15%时最大值为89%,但乳化性有所降低,起泡性及稳定性也大约下降了40%。     

采用微射流处理改变番茄籽分离蛋白的理化性质及结构

碱溶酸沉法所制备的番茄籽分离蛋白,其溶解性等功能性质较差。以番茄籽分离蛋白为原料,研究微射流均质对其功能性质及结构的影响。结果表明：微射流均质过程中番茄籽分离蛋白的结构变化与其功能性质的改变存在关联。微射流均质提高了番茄籽分离蛋白的溶解性、乳化性及乳化稳定性;均质后的番茄籽蛋白粒径更小,分布更均匀;暴露巯基和总巯基含量减少;分子内部疏水基团暴露,表面疏水性提高;蛋白晶体结构变化不大;蛋白质的二级结构发生了变化,α-螺旋、无规卷曲、β-转角均减少,而β-折叠增加。这些变化说明,微射流均质处理使蛋白分子发生了伸展或折叠,从而改变其功能性质。     

Modifications of soy protein isolates using combined extrusion pre-treatment and controlled enzymatic hydrolysis for improved emulsifying properties

Effects of combined extrusion pre-treatment and controlled enzymatic hydrolysis on the physico-chemical properties and emulsifying properties of soy protein isolates (SPI) have been investigated. Results showed that extrusion pre-treatment caused a marked improvement in the accessibility of SPI to enzymatic hydrolysis, resulting in changes in degree of hydrolysis (DH), protein solubility (PS), surface hydrophobicity (H₀) and molecular weight distributions (MWD) for ESPIH (extrusion pre-treated SPI hydrolysates). It was observed that emulsion systems formed by control SPI or SPIH (SPI hydrolysates) (20% v/v oil, 1.6% w/v emulsifier, and pH 7.0) were unstable over a quiescent storage period of 21 days, due to bridging flocculation and creaming. However, ESPIH (9.1% DH) was capable of producing a very fine emulsion (d₃₂ = 0.42 μm, d₄₃ = 2.01 μm) which remained stable over a long term quiescent storage. Various surface properties of ESPIH products have also been studied in relation to DH and emulsifying functionalities. It was suggested that significantly increased protein solubility and decreased molecular weight could be the main reasons for the greatly improved emulsifying capability of ESPIH. This study demonstrated that modified soy protein could be an excellent emulsifying agent for food and other applications. It also demonstrated that combined extrusion pre-treatment and enzymatic hydrolysis could be a highly effective method for functionality modification of globular proteins.     

不同水解度猪骨蛋白水解物对水包油型乳状液乳化特性的影响

摘 要：研究不同水解度的猪骨蛋白水解物（porcine bone protein hydrolysates,PBPH）对水包油乳状液的乳化特性的影响。采用碱性蛋白酶对猪骨蛋白进行水解0、1、2、3、4、5?h得到水解度分别为0%、5.6%、7.8%、11.1%、14.3%、17.2%的样品,分别测定PBPH的乳化活性、乳化稳定性、Zeta电位、乳状液微观结构的变化以及活性肽的分子质量分布。PBPH乳化性研究表明,随着水解度的增加,乳状液的乳化活性和乳化稳定性呈现先增加后降低的趋势（P＜0.05）,水解度为11.1%时的PBPH所形成的乳状液稳定性最高,这可能与其具有最高的表面疏水性、最高的Zeta电位、最小的体积平均粒径和最均匀的液滴分布有关。分子排阻色谱测定结果表明,随着水解度的增加,酶解产物的分子质量分布表现出大分子肽含量逐渐减少,小分子肽含量逐渐增多,水解过程中伴有多肽链的断裂和蛋白质的聚集,结构变化影响不同水解度的PBPH功能性质的变化,这进一步解释了乳化性变化的原因。由此可以得出,PBPH在水解时间为3?h?（水解度为11.1%）的适度水解的条件下,其乳化性最好,可以用于制备高物理稳定性的乳状液。     

限制性酶解对豆粉相关性质的影响

为降低豆粉的致敏性,扩大其应用,采用限制性酶解制备豆粉。以木瓜蛋白酶、风味蛋白酶和碱性蛋白酶为限制性酶解用酶,研究不同的酶制剂及酶解时间对豆粉的致敏性、溶解性、表面疏水性及乳化性的影响,并对豆粉进行感官评价。结果表明:随着酶解时间的延长,豆粉的致敏性降低,溶解性、表面疏水性、乳化活性和乳化稳定性增加;其中利用木瓜蛋白酶酶解30 min制备的豆粉致敏原含量最低,为1. 95%,溶解性最高,为88. 55%,乳化活性及乳化稳定性最大,分别为182. 4 m2/g和120. 8 min;利用SDS-PAGE电泳发现,酶解作用使豆粉蛋白质中的7S和11S降解,生成小分子的肽类,从而降低豆粉的致敏性;利用木瓜蛋白酶酶解20 min制备的豆粉口感与传统市售豆粉相似。     

Influence of degree of hydrolysis on functional properties,antioxidant activity and ACE inhibitory activity of peanut protein hydrolysate

Functional properties, antioxidant and Angiotensin-converting enzyme (ACE) inhibitory activities of peanut protein isolate (PPI) and peanut protein hydrolysate (PPH) prepared using Alcalase, at different (10%, 20%, 30% and 40%) degrees of hydrolysis, (DH) were investigated. Hydrolysis (at DH > 10%) significantly (p < 0.05) improved the solubility (>80%) of PPI, especially in the pH range of 4–6. However, PPI showed better emulsifying and foaming properties than PPH (p < 0.05). As DH increased, ferrous ion chelating activity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity and ACE inhibitory activity of PPH increased, while reducing power decreased (p < 0.05). Bleaching of beta-carotene by linoleic acid was suppressed better by PPI and PPH at 10% DH than of PPH at higher DH. Thus, the results reveal that DH affects functional properties, antioxidant and ACE inhibitory activities of peanut protein.     

Enzymatic hydrolysis and their effects on conformational and functional properties of peanut protein isolate

The effects of limited enzymatic hydrolysis by Alcalase on the conformational and functional properties of peanut (Arachis hypogaea L.) protein isolate (PPI) were investigated. Acid subunits of arachin were most susceptible to Alcalase hydrolysis, followed by conarachin and the basic subunits of arachin. Enzymatic hydrolysis increased the thermal stability of arachin and led to a sharp increase in the number of disulphide bonds with a decrease of the sulphydryl group in PPI hydrolysates in comparison with PPI. The analysis of intrinsic fluorescence spectra indicated a more moveable tertiary conformation of PPI hydrolysates than PPI. The limited emzymatic hydrolysis improved the functional properties of PPI, such as protein solubility and gel-forming ability, but impaired the emulsifying activity index.     

改性对玉米蛋白质功能性质和结构的影响(I)酶解

蛋白质的食品功能性质主要由其结构决定 ,改性是改善或加强某些食物蛋白的功能性质的有效方法。通过Asl.398枯草杆菌中性蛋白酶对玉米蛋白质的水解改性发现 ,Asl.398蛋白酶对玉米蛋白质的最大水解度为 2 9.47% ;随水解度的增大 ,水解物的表面疏水性先增大后减少 ,分子柔性不断增大 ,溶液粘度不断降低 ,这表明水解使玉米蛋白结构发生了明显变化。而随着水解度的增大 ,玉米蛋白质的水溶性大幅度提升 ,水解度为 3.0 %的水解物的乳化活性最大 ,而水解度为 9.0 %的水解物的乳化稳定性最高     

Functional Properties and Bioactivities of Pine Nut (Pinus gerardiana) Protein Isolates and Its Enzymatic Hydrolysates

The functional properties and bioactivities of the pine nut protein isolates (PPI) and its enzymatic hydrolysates (PPH) prepared with Alcalase at 5 %, 10 %, 15 % and 25 % degree of hydrolysis (DH) were studied. The solubility of PPH significantly increased (p?<?0.05) with the increase of the DH, while the foaming capacity of PPH was only improved at a low DH. However, enzymatic hydrolysis reduced the emulsifying capacity of PPH. The DPPH radical scavenging and inhibition of linoleic acid oxidation activities of PPH were significantly improved by a low DH (5 %) compared with those of PPH with a higher DH and the original PPI (p?<?0.05). The reducing power of PPH at all DH decreased in comparison to that of the original PPI. Potent angiotensin-converting enzyme (ACE) inhibitory peptides could be generated by hydrolysis with Alcalase, and the ACE inhibitory activity of PPH increased (p?<?0.05) with the DH. These results revealed that a low degree of enzymatic hydrolysis was appropriate to obtain PPH with improved functional properties and good antioxidant activities, while a high degree of hydrolysis was essential to obtain highly potent ACE inhibitory peptides from PPI. These results suggest that the control of the DH may be an effective strategy to modify specific functional and bioactive properties of PPH, and PPH has potential as a functional food ingredient for related functional and health benefits.     

Functional properties of limited hydrolysed cross‐linked casein–gelatin composites

A casein–gelatin composite was prepared by cross‐linking of caseinate and bovine gelatin with a microbial transglutaminase, and the impact of limited proteolysis by trypsin on some functional properties of the composite was investigated in the present work. Two hydrolysed composites were prepared with degree of hydrolysis (DH) of 1 and 2% and analysed by SDS‐PAGE to reflect polypeptide profiles. Some functional properties of the two hydrolysed composites were evaluated, among which solubility, digestibility in vitro, surface hydrophobicity and emulsifying properties showed dependence on the DH. Limited proteolysis of the composite improved its solubility in pH 3–10, especially when the DH was 2%. Compared to the composite, the hydrolysed composites showed an increased emulsifying activity index (about 357–408%), emulsion stability index (about 23–28%) and digestibility in vitro (about 65–80% for pepsin, whereas 2–3% for pepsin–trypsin hydrolysis), together with a decreased surface hydrophobicity (about 55–62%) and oil absorption capacity (about 20–23%). The applied proteolysis also led to the aqueous dispersions of the two hydrolysed composites much lower apparent viscosity, storage and loss modulus.     

酶法制备不同水解度高温豆粕水解产物的理化特性研究

采用Alcalase酶和木瓜蛋白酶分别对高温大豆粕进行酶解,通过控制酶解反应得到水解度为5%、10%和15%的6种水解产物,研究两种酶对不同水解度的水解产物理化特性的影响。结果表明,Alcalase酶和木瓜蛋白酶均可产生6种不同分子量范围的水解产物,但各部分比例具有显著差异(P0.5),其平均分子量随水解度的增加逐渐减少,Alcalase酶的水解产物中小于2562 Da小分子量肽所占比例更高。豆粕蛋白的疏水基团在酶解反应中发生暴露与断裂的数量差,导致其表面疏水性随水解度增加呈现先下降再上升的变化,即水解度为10%的表面疏水性最低。zeta电势的绝对值随水解度不断上升,分子间的斥力增大,相同水解度下两种酶对zeta电势的影响并不显著。此外,在pH值为3、5、7和9时,水解产物的溶解性随着水解度的增加而逐渐增高,乳化活性和乳化稳定性则逐渐降低。