藤黄微球菌(Micrococcus luteus)KDF1胞外蛋白酶酶学性质与水解大豆蛋白产物研究

对1株分离于克东腐乳的优势菌株藤黄微球菌(Micrococcus luteus)KDF1胞外蛋白酶的酶学性质及其水解大豆分离蛋白(soybean protein isolates,SPI)产生的氨基酸图谱进行研究。以酪蛋白为底物,利用酶学技术研究了温度、pH、NaCl、乙醇和金属离子对藤黄微球菌(Micrococcus luteus)KDF1胞外蛋白酶的活性和稳定性的影响。研究表明藤黄微球菌(Micrococcus luteus)KDF1胞外蛋白酶的最适反应温度为40℃,在20⁴0℃范围内具有良好的稳定性;最适反应pH为9.0,在pH 7.040℃范围内具有良好的稳定性;最适反应pH为9.0,在pH 7.0⁹.0范围内具有良好的稳定性;在9%(w/v)NaCl和8%(w/v)乙醇中分别表现出良好的催化活性和稳定性;Ca2+和Mg2+可显著增强藤黄微球菌(Micrococcus luteus)KDF1胞外蛋白酶的催化活性。利用氨基酸分析技术检测藤黄微球菌(Micrococcus luteus)KDF1胞外蛋白酶水解SPI产生的氨基酸图谱,结果表明总游离氨基酸、必需氨基酸和风味氨基酸含量明显增加。上述结果表明藤黄微球菌(Micrococcus luteus)KDF1胞外蛋白酶在酶法促熟和酶法发酵腐乳领域有潜在的应用价值。     

Rheological properties of soy protein hydrolysates obtained from limited enzymatic hydrolysis

Soy protein products hexane-defatted soy flour, extruded-expelled soy flour, soy protein concentrate and soy protein isolate, were modified by using the enzyme bromelain to 2% and 4% degrees of hydrolysis (DH). Peptide profiles, water solubility, and rheological properties including dynamic shear, large deformation, and apparent viscosities of resulting hydrolysates were determined. Protein subunits profiles for the hydrolysed isolates and concentrates were extensively altered by the treatment while only minor changes were observed for the hydrolysed flours. Water solubility profiles of all hydrolysates in the pH range of 3.0-7.0 were enhanced by hydrolysis. For the unhydrolysed controls, the isolate had the highest storage modulus (G′), followed by the concentrate, the extruded-expelled flour and the hexane-defatted flour. The hydrolysates retained some of their gelling ability even though the losses in storage modulus (G′) were substantial. After heating step to 95 °C, the G′ values of all substrates at 25 °C decreased with increase in DH. Texture profile analyses of the soy protein gels were also lower in hardness after hydrolysis. The Power Law model provided excellent fit to hydrolysate dispersions flow (R²>0.99). Hydrolysis decreased the consistency coefficients of dispersion and increased flow behavior index resulting in thinner dispersions. These results suggest that limited protease hydrolysis of various soy protein meals with bromelain produce soy protein ingredients with modified rheological properties.     

糯米蛋白提取工艺优化及其水解物性质的测定

以糯米为原料,采用碱性蛋白酶水解法提取了糯米蛋白。就影响糯米蛋白提取率的5个因素:料液比(g/mL)、加酶量(E/S)、pH、温度和提取时间进行单因素实验和正交实验。研究确立了提取糯米蛋白的最佳工艺条件为料液比1:12,加酶量2%,pH9,温度45℃,提取时间3h。在此条件下,糯米蛋白的提取率可达8.529%。实验表明,糯米蛋白水解物是一类天然的抗氧化氨基酸及其聚合物。     

Interfacial and foaming properties of soy protein and their hydrolysates

The objective of the work was to study the impact of soy protein hydrolysis on foaming and interfacial properties and to analyze the relationship between them. As starting material a sample of commercial soy protein isolate was used (SP) and hydrolysates were produced by an enzymatic reaction, giving hydrolysates from 0.4% to 5.35% degree of hydrolysis (DH).In this contribution we have determined foam overrun (FO), stability against liquid drainage and foam collapse, and the apparent viscosity of foams produced by a whipping method. The surface properties determined were the adsorption isotherm and surface dilatational properties of two hydrolysates (2 and 5.35% DH, H1 and H2 respectively).The hydrolysis of soy proteins increased the surface activity at bulk concentrations where SP adopts a condensed conformation at the monolayer. At concentrations where it adopts a more expanded conformation a very low degree of hydrolysis (H1) also promoted the enhancement of surface activity. However, at 5.35% degree of hydrolysis (H2) the surface activity decreased. Moreover, H2 presented lower surface activity than H1 at every bulk concentration.The hydrolysis increased the elastic component of the dilatational modulus and decreased phase angle of films at bulk concentrations below that corresponding to the collapse of SP monolayer (2% bulk protein).SP hydrolysis increased foam overrun and the stability against drainage that could be related to increased surface activity of protein hydrolysates. However, the collapse of foams was promoted by hydrolysis and could be ascribed to a decrease of the relative viscoelasticity (higher phase angle) of surface films.The results point out that a low degree of hydrolysis (2–5%) would be enough to improve the surface activity of SP, decrease foam drainage and maintaining a considerable viscoelasticity of the surface films to retard foam collapse.     

大豆分离蛋白酶解液体外抗氧化性的研究

以大豆分离蛋白为底物，以抗氧化性为指标，从6种蛋白酶中筛选出碱性内切蛋白酶为最佳水解酶，优化了其最佳水解条件，并测定了碱性内切蛋白酶水解大豆分离蛋白所得酶解液的亚油酸过氧化抑制率和清除氧自由基活力。结果表明，碱性内切蛋白酶最佳水解条件为T=55℃，pH=7．5，E／[S]=5％，[S]=4．5％，水解时间t=3h，其水解大豆分离蛋白所得酶解液的亚油酸过氧化抑制率为28．4％，清除氧自由基活力为45．6％。     

Antioxidant activities and functional properties of soy protein isolate hydrolysates obtained using microbial proteases

Soy protein isolate (SPI) hydrolysates were prepared using microbial proteases to produce peptides with antioxidant activity. The process parameters (substrate and enzyme concentrations), hydrolysis time, functional properties and the effects of ultrafiltration were further investigated. The results showed that the soy protein isolate exhibited a 7.0‐fold increase in antioxidant activity after hydrolysis. The hydrolysis parameters, defined by the experimental design, were a substrate concentration of 90 mg mL^?1 and the addition of 70.0 U of protease per mL of reaction. The maximum antioxidant activities were observed between 120 and 180 min of hydrolysis, where the degree of hydrolysis was approximately 20.0%. The hydrolysis increased solubility of the soy protein isolate; however, the hydrolysates exhibited a tendency to decrease in the interfacial activities and the heat stability. The SPI hydrolysates fractions obtained by ultrafiltration showed that the enzymatic hydrolysis resulted in samples with homogenous size and strong antioxidant activity.     

枯草芽孢杆菌HS18碱性蛋白酶分离纯化及其性质研究

从合浦珠母贝肠道中分离鉴定到酶菌株枯草芽孢杆菌（Bacillus subtilis）HS18,将枯草芽孢杆菌HS18的发酵液,经过硫酸铵盐析、DEAE-Sephadex A-50柱层析、Sephadex G-100柱层析3步纯化后得到了单一的酶蛋白,回收率为11.4%;经SDS-聚丙烯酰胺凝胶电泳测得酶蛋白分子量约为31ku;该蛋白酶最适反应温度为50℃,最适pH10.0;K+及Na+对酶有明显激活作用;丝氨酸蛋白酶特异性抑制剂（PMSF）能强烈抑制酶活性。表明所纯化到的蛋白酶为丝氨酸碱性蛋白酶。      

大豆球蛋白酶解物的抗氧化性及汞离子结合特性的研究

以未还原大豆球蛋白水解物为对照,研究了还原大豆球蛋白胃酶酶解物的抗氧化性及汞离子结合特性。结果表明:还原蛋白酶解物巯基含量为117.5μmol/g,是未还原蛋白酶解物的76.8倍。还原蛋白酶解物分子质量更小,疏水性与未还原蛋白酶解物相差不大。还原蛋白酶解物对超氧阴离子自由基、羟基自由基、DPPH自由基清除的IC50分别为18、20和0.7 mg/m L,当质量浓度为2 mg/m L时,Fe3+还原能力为0.557,汞离子结合量为8.02 mg/g,还原蛋白酶解物的抗氧化性和汞离子结合能力显著优于未还原酶解物。说明还原大豆球蛋白酶解物具有一定的汞离子解毒潜能。     

鱿鱼水解物的抗氧化性及乳化性的研究

以鱿鱼为原料,经酶解后得到不同水解时间的水解物,研究不同鱿鱼水解物的抗氧化性、乳化性及起泡性变化.实验表明,随水解过程的进行,鱿鱼水解物DH逐渐增大,之后增加缓慢:对羟自由基清除活性和还原能力与DH呈正相关;对超氧阴离子和DPPH自由基清除活性呈先增加后基本不变的趋势;氮溶解指数逐渐增加.同时,经酶解的鱿鱼水解物较酶解前鱿鱼浆的乳化性、乳化稳定性及起泡性都发生了改变.     

Fractionation and identification of a novel hypocholesterolemic peptide derived from soy protein Alcalase hydrolysates

A novel hypocholesterolemic peptide was fractionated by gradient ethanol elution from a macroporous adsorption resin (MAR DA201-C), and then separated on Sephadex G-15 and RP-HPLC from a soy protein hydrolysate (SAPH DH 18%). Identification of the hypocholesterolemic peptide structure was accomplished with HPLC–MS. The peptide with the highest hypocholesterolemic activity was found in 75% ethanol fraction among the four fractions from gradient ethanol elution with MAR DA201-C. The calculated average hydrophobicity by amino acid composition of each ethanol eluted fraction suggested that the peptides could be separated in terms of hydrophobicity with MAR DA201-C. Four peaks were obtained with further fractionation on Sephadex G-15, the highest cholesterol micellar solubility inhibition rate, 81.3%, was obtained in Peak 2, corresponding to the molecular weight fraction of 300–800 Da. Fifteen main peaks were obtained with RP-HPLC fractionation, the highest cholesterol micellar solubility inhibition rate (94.3%) was in Peak 7. The amino acid sequence of this peptide was identified as WGAPSL with LC–MS and amino acid composition analysis.     

Chia protein hydrolysates: characterisation and emulsifying properties

The evaluation of functional properties of different chia protein hydrolysates (CPH) and their application in O/W emulsions were studied. Enzymatic treatments with pepsin, pancreatin or the sequential action of pepsin–pancreatin were applied to hydrolyse a chia protein concentrate (CPC). Oil-in-water emulsions stabilised with CPC or these CPHs, with or without chia mucilage, were prepared at pH 7 or 10. Particle size, global stability, ζ-potential and rheological measurement of emulsions were determined. CPH presented higher (P ≤ 0.05) solubility and surface hydrophobicity levels, exhibiting better emulsifying properties than CPC. Emulsions with CPH presented smaller (P ≤ 0.05) droplet sizes than those with CPC. Regarding to physicochemical stability, emulsions at pH 7 were less stable than those at pH 10, showing destabilisation by creaming and coalescence. The addition of chia mucilage increased the apparent viscosity of emulsions and led to modifications in their fluid behaviour, exhibiting an interesting role as a thickening agent.     

Antioxidant effects and reaction volatiles from heated mixture of soy protein hydrolysates and coconut oil

Food Science and Biotechnology - Soy protein hydrolysates (SPHs) are prepared from soybean meal using commercially available protease enzymes and acid/alkali treatment. The antioxidant properties...     

地衣芽孢杆菌2709蛋白酶分离纯化与性质

采用盐析、DEAE阴离子交换层析、凝胶层析等步骤,从地衣芽孢杆菌(B·licheniformis)2709的发酵液中获得了电泳纯的碱性蛋白酶。结果发现:提纯酶的活力达61069U/mg,纯化倍数:38.7,活性回收率:19.3%,去酰氨度:20.9%.并研究了该酶的基本酶学特性,碱性蛋白酶最适反应温度为50℃,最适作用pH为10.0。40℃保温2h后该酶保持80%以上的活力,在pH8～11之间有较高的pH稳定性。     

Applications of soy protein hydrolysates in the emerging functional foods: a review

Several applications of protein hydrolysates have been documented including gelation, solubility and emulsifying properties. However, very rare reviews have solely explored the potentials of soy protein hydrolysates (SPHs). Varying and abundant pieces of information on the physicochemical properties of soy proteins, such as foaming, solubility, emulsifying, gelling, fat- and water-holding capacities, suggest their hydrolysates to be equally or more important. In this regard, this review highlights the different methods that have been used to prepare SPHs, coupled with the most promising applications and potentials of SPHs. Nonetheless, further investigations are necessary to validate the potentialities of SPHs as food agents for the emerging functional foods.     

制备工艺对油莎豆油理化性质、营养成分和氧化稳定性的影响

为了解析大豆水解肽（Soy hydrolyzed peptide,SHP）-茶皂素（Tea Saponin,TS）复合体系中TS对SHP结构及功能性质的影响,比较分析SHP与TS在1:0、1:0.5、1:1、1:2（w/w）比值下的作用机制。采用傅里叶变换红外光谱、荧光光谱、紫外-可见吸收光谱表征了SHP-TS复合物中蛋白的空间结构变化;并以乳化性、抗氧化性、平均粒径、ζ-电位为指标阐明了复合物中SHP构象改变与功能特性之间的关系。结果表明,添加TS可以使SHP的二级结构发生改变,氢键参与了SHP-TS复合物的形成;随着TS添加量的增加,荧光猝灭强度增强;SHP与TS发生强相互作用,空间构象发生改变。另外,随着TS占比的增加,复合物的乳化性、抗氧化性增强,平均粒径呈现出先下降后上升的趋势,ζ-电位绝对值呈先上升后下降的趋势。当SHP:TS为1:1（w/w）时得到综合性比较优异的SHP-TS复合物,与SHP单一体系相比,此时复合物的乳化稳定系数最大;乳液平均粒径最小、ζ-电位的绝对值最高。该研究有望为食品工业中的新型乳化剂的开发提供一定的理论基础。

     

大豆蛋白酶解产物抗氧化活性与水解度相关性研究

利用碱性蛋白酶Alcalase 2.4L水解大豆分离蛋白,研究了底物浓度、加酶量、p H、温度因素对酶解液水解度和还原力的影响,并在此基础上用响应面分析法优化酶水解条件。以还原力为主要指标考察酶解产物的抗氧化活性,通过水解度与还原力的比较,得到Alcalase 2.4L碱性蛋白酶酶解大豆分离蛋白产物的抗氧化活性与水解度之间没有直接线性关系。在实验得到的最佳条件下制备的大豆肽抗氧化活性良好,具有良好的应用前景。     

Functional properties of protein hydrolysates from Riceberry rice bran

Protein hydrolysate from pigmented Riceberry rice bran has great potential to be used in food products due to its protein content and antioxidative activities. In this study, characteristics, solubility, heat stability and emulsification properties of protein hydrolysates from the bran fraction of two rice cultivars, commercial rice bran (CBH) and Riceberry bran (RBH), were investigated. Both CBH and RBH showed the lowest solubility near their isoelectric point between pH 2 and 3. Solubility of RBH increased with increasing pH as the hydrolysates became more negatively charged; however, solubility of CBH was less dependent on pH. Heating did not significantly affect solubility of both hydrolysates which could be due to reduced aggregation of low‐molecular weight peptides and/or the exposure of charged and polar groups after hydrolysis. Oil‐in‐water emulsions stabilised by RBH were more stable compared to those stabilised by CBH. Maximum stability was achieved with RBH at pH 6 where no creaming was observed after 14 day storage. Higher stability could be due to increased surface protein coverage, more negative charge and higher viscosity of RBH‐stabilised emulsions. In addition, higher carbohydrate content and the presence of flavonoid could also contribute to an increase in stability. These results can be applied in food products using rice bran protein hydrolysate as nutritional ingredients.     

Purification and characterization of antioxidative peptides derived from rice bran protein hydrolysates

Rice bran protein fraction (RBPF)—albumin, globulin, glutelin and prolamin were hydrolyzed with proteases M, N, P, S and pepsin under their optimal conditions for 24 h. Hydrolysates of various hydrolysis periods were collected and subjected to peptide mapping and the antioxidative activity measured by the 2,2-Azino-bis-3-ethylbenzothiazoline-6-sulfonic Acid (ABTS) method. Protease M hydrolysates showed high degree of hydrolysis (DH), but low antioxidative activity. On the contrary, pepsin hydrolysates showed low DH with high activity. Albumin and globulin hydrolysates had higher DH values, but lower values for glutelin and prolamin. The globulin hydrolysate (Opep2) from 2 h-pepsin hydrolysis was separated by using three consecutive purification steps with RP-HPLC. Nineteen antioxidative peptides were isolated and their amino acid sequences were determined by a gas-phase protein sequencer and MALDI-TOF mass spectrometry. These peptides were composed of 6–30 amino acid residues with molecular masses ranging from 670–3,611 Da. Tyr-Leu-Ala-Gly-Met-Asn had the highest antioxidative activity among them.