转谷氨酰胺酶对乳蛋白质的改性作用

转谷氨酰胺酶是催化酰基转移反应的一种酶,可使蛋白质或多肽之间发生共价交联反应。本文介绍了转谷氨酰胺酶对牛乳蛋白质凝胶特性、乳化性、热稳定性、成膜性等特性的改性作用及其在乳品加工中的应用。      

转谷氨酰胺酶交联作用对乳蛋白功能特性的影响

转谷氨酰胺酶可用于蛋白交联,改性蛋白质的组织结构和功能特性,在食品工业中具有广阔的应用前景。本文介绍了转谷氨酰胺酶的作用机制、对乳蛋白功能特性的影响以及在酸奶生产中的应用等。     

变性对转谷氨酰胺酶在乳蛋白间交联影响初探

利用SDS-PAGE电泳结合凝胶成像分析技术，比较了在非变性、加入还原剂变性和加热后再加入还原剂变性三种条件下转谷氨酰胺酶对酪蛋白和乳清蛋白之间的交联情况。结果表明：在非变性条件下，酪蛋白质量分数下降96％，乳清蛋白下降15％，酪蛋白和乳清蛋白几乎不能交联。超分子量聚合物是酪蛋白单一聚合物，α-乳白蛋白形成部分低聚体；在加入还原剂时，酪蛋白质量分数下降86％，乳清蛋白下降30％，反应4h后有少量乳清蛋白和酪蛋白中某一组分交联；预热更有助于酪蛋白和乳清蛋白聚合，在第三种条件下，反应24h后乳清蛋白下降60％。     

转谷氨酰胺酶对大豆分离蛋白的改性研究

以微生物转谷氨酰胺酶(Microbial Transglutaminase，MTGase)对大豆分离蛋白(Soy Protein Isolate，SPI)进行改性。结果显示改性后SPI的凝胶性得到明显改善；乳化活性下降，乳化稳定性提高；溶解性下降，但在等电点附近溶解性则略有上升。MTGase促进SPI的交联形成了较大的聚合物，改变了蛋白质的结构，使内部的疏水性氨基酸暴露出来，增加了蛋白质的表面疏水性，同时也使蛋白质分子之间彼此连接形成空间网络结构。     

转谷氨酰胺酶改性可食用膜的研究进展

转谷氨酰胺酶可催化蛋白发生交联反应,从而改性可食用蛋白膜和复合膜的组织结构和特性,如抗拉强度、断裂伸长率、阻水性、阻油性、透氧系数等,在食品工业中具有广阔的应用前景.本文介绍转谷氨酰胺酶改性对大豆蛋白可食用膜、乳清蛋白可食用膜、明胶可食用膜和复合膜的特性影响以及应用前景.     

转谷氨酰胺酶对食品的粘合作用

<正> 在加工食品中添加酶以改变制成品的性质,是非常普遍的做法。一般加工食品所采用的酶,如淀粉酶和蛋白酶等,其作用在于把食品中较粗糙的成分分解成较微小的颗粒。但转谷氨酰胺酶的作用却相反——它利用蛋白质与蛋白质之间会互相形成共价键的特性,催化食品中蛋白质的聚合作用和交联反应(蛋白质交联模拟图见于图一),从而使小块状食品粘合成理想的形状,并改进其硬度和弹性,提高食品的感观质量。 转谷氨酰胺酶基本上存在于哺乳类动物的肝脏和血液之中,也存在于鱼类的肌肉内,甚至在微生物中。作为工业     

转谷氨酰胺酶改性对明胶耐酶解性的影响

以转谷氨酰胺酶改性明胶的耐酶解性为关注点,通过单因素试验和均匀设计试验研究转谷氨酰胺酶浓度、改性pH值、改性温度和改性时间等因素对改性明胶耐酶解性的影响。通过均匀试验得到的最优改性条件为:转谷氨酰胺酶质量浓度为0.20 g/L,改性pH 6.0,改性温度44℃,改性时间35 min。与未改性明胶相比较,改性明胶的耐酶解能力提高了14.44%。本研究结果表明转谷氨酰胺酶改性可以显著提高明胶的耐酶解能力。     

转谷氨酰胺酶对大豆分离蛋白的改性研究

以微生物转谷氨酰胺酶(MicrobialTransglutaminase,MTGase)对大豆分离蛋白(SoyProteinIsolate,SPI)进行改性。结果显示改性后SPI的凝胶性得到明显改善;乳化活性下降,乳化稳定性提高;溶解性下降,但在等电点附近溶解性则略有上升。MTGase促进SPI的交联形成了较大的聚合物,改变了蛋白质的结构,使内部的疏水性氨基酸暴露出来,增加了蛋白质的表面疏水性,同时也使蛋白质分子之间彼此连接形成空间网络结构。     

转谷氨酰胺酶在肉制品中的应用

对转谷氨酰胺酶的性质、作用机理作了简要介绍，并概述了它在肉制品中的应用。     

转谷氨酰胺酶改性大豆分离蛋白条件研究

利用微生物转谷氨酰胺酶(MTGase)对大豆分离蛋白(SPI)进行改性,探讨pH、反应温度、反应时间、底物浓度、酶/蛋白质比对SPI改性影响,采用正交试验优化改性条件。结果显示,酶/蛋白质比和底物浓度对SPI改性影响较小;pH、温度和时间对该改性作用影响较大,该3种因素对SPI改性影响大小依次为pH、温度和时间;MTGase改性SPI的最佳条件为pH 5.5、温度55℃、时间30 min、底物浓度2.0%、酶/蛋白质比10 U/g。     

转谷氨酰胺酶对荞麦蛋白功能特性的影响

微生物转谷氨酰胺酶(MTGase)能够使荞麦蛋白(BWP)的大部分球蛋白亚基被聚合,而几乎不能使分子量低于36kDa的碱性亚基聚合。BWP聚合物(催化时间<60min)的溶解度(PS)较BWP显著增加,聚合物的PS随反应时间的延长而降低;MTGase催化BWP反应120min可明显降低其PS(P<0.05)。聚合反应能提高BWP的持水能力(WH)和持油能力(FA),且BWP聚合物的FA随反应时间的增加而增强。适当的交联会使BWP的起泡性能增加,但继续提高交联度(延长酶反应时间),BWP的起泡性能反而降低。BWP聚合物的乳化活性指数(EAI)降低,乳化液稳定性(ES)却增强。     

酪蛋白的转谷氨酰胺酶氨基葡萄糖修饰与功能性变化

在37℃、pH值为7.5和氨基葡萄糖存在下,利用转谷氨酰胺酶(EC 2.3.2.13)对酪蛋白进行交联修饰制备修饰酪蛋白;用十二烷基磺酸钠-聚丙烯酰胺凝胶电泳和高效液相色谱分析证实酪蛋白同时发生交联与糖基结合,且反应4 h时每摩酪蛋白可结合1.2摩葡萄糖.与酪蛋白相比,交联酪蛋白的溶解性质和起泡性质受损,而修饰酪蛋白产品的溶解性质得到改善,起泡性质尤其是泡沫稳定性质显著提高.在蛋白质质量浓度为1 g/L时,修饰酪蛋白的起泡能力和泡沫稳定性分别比酪蛋白提高8.6%和21%;质量浓度为100 g/L的修饰酪蛋白分散液表现出非牛顿流体特性,表观黏度显著高于交联酪蛋白或酪蛋白.     

Modification in physical properties of rice gel by microbial transglutaminase

BACKGROUND: Microbial transglutaminase (MTGase) may catalyse the cross‐linking between a peptide‐bound glutaminyl residue and an ε‐amino group of lysine residue in protein. MTGase has been used to modify many food proteins for improving the physical properties of products. However, its effect on the physical properties of rice products has not been investigated before. The present study aimed to investigate the effect of MTGase, as an additive in rice flour, on the rheological, textural and thermal properties of rice gel. RESULTS: Both the elastic and the viscous moduli of rice gel were increased as a result of the addition of MTGase to rice flour. The addition of MTGase at 0.01–0.3 U mg^?1 increased textural parameters (hardness and gumminess) and rheological properties. Differential scanning calorimetry also showed that MTGase treatment decreased the enthalpy change in gelation. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) confirmed that rice proteins were polymerised through the MTGase reaction. CONCLUSION: The present study proved that the cross‐linking of protein molecules in rice flour by the action of MTGase may improve the physical properties of rice gel. The addition of MTGase in rice flour in an adequate amount is essential for achieving appropriate physical properties of the product. Copyright © 2008 Society of Chemical Industry     

谷氨酰胺转氨酶交联对牦牛乳曲拉酪蛋白功能性质的影响

以曲拉和荷斯坦牛乳酪蛋白为原料,利用安全、高效的谷氨酰胺转氨酶对其进行交联修饰,研究谷氨酰胺转氨酶对酪蛋白功能性质的影响,测定交联前后样品的持水性、持油性、热稳定性、黏度、起泡性。结果表明,牦牛乳曲拉酪蛋白和荷斯坦牛乳酪蛋白经过谷氨酰胺转氨酶交联后,两种酪蛋白的交联度分别可达到20.04%(p<0.05)和25.15%(p<0.05),曲拉酪蛋白的持水性、热稳定性、黏度和泡沫稳定性显著增加(p<0.05),荷斯坦酪蛋白的黏度和热稳定性显著增加(p<0.05),其余性质均无显著差异。研究结果能为酶法改性酪蛋白的工业化生产提供理论依据。      

转谷氨酰胺酶交联时间对玉米胚芽蛋白功能性质的影响

为解决玉米胚芽蛋白溶解性低的问题,提高其在食品工业领域的实际应用,以玉米胚芽蛋白为原料,通过酶解、转谷氨酰胺酶(TGase)交联,制备了不同交联时间的玉米胚芽蛋白,利用红外光谱仪和粒度分析仪分析玉米胚芽蛋白结构和表面性质的变化,并检测其溶解性、乳化性、起泡性等功能性质。结果表明：随着交联时间的延长,玉米胚芽蛋白的溶解性、起泡能力、持水性、乳化活性逐渐增强,乳化稳定性变化趋势与之相反,泡沫稳定性先升后降,持油性先降后升;与原样相比,交联3 h的玉米胚芽蛋白的乳化活性提高了16.7倍,持水性和持油性分别增加了9.16%和8.71%;TGase交联反应改变了玉米胚芽蛋白的二级结构,酰胺Ⅰ带的伸缩振动增强, β-转角增多,蛋白质粒径和Zeta电位发生改变,蛋白质结构和表面性质的改变造成其功能性质的变化。综合来看,交联3 h的玉米胚芽蛋白的功能性质表现最佳。     

Modification of the properties of milk protein films by gamma radiation and polysaccharide addition

This study has demonstrated that gamma radiation induced an improvement of barrier properties and tensile strength of films containing calcium caseinate, whey protein isolate and glycerol (1:1:1) through creation of a crosslinked β‐structure. Up to 32 kGy the effect was accompanied by an increase in rigidity and was larger with increasing radiation dose. The irradiation of protein solutions also caused improvement of puncture strength of films prepared with potato starch, soluble potato starch or sodium alginate addition (at a level of 50 g kg^?1 of total proteins). Addition of potato starch did not influence mechanical properties of films but significantly improved barrier properties. Addition of sodium alginate resulted in improvement of both puncture strength and barrier properties. Addition of sodium alginate to irradiated protein solution resulted in films revealing the greatest improvement in properties. Gels prepared using irradiated protein solutions mixed with calcium salt were stronger than gels prepared using non‐irradiated solutions owing to the preferred binding of calcium ions to the crosslinked protein network. Presence of sodium alginate and potato starch weakened the interaction of proteins with calcium ions owing to entrapment of proteins in the polysaccharide network, while addition of soluble potato starch promoted these interactions. Copyright © 2006 Society of Chemical Industry     

谷氨酰胺转胺酶改性对花生分离蛋白某些功能性质的影响

利用微生物产谷氨酰胺转胺酶(MTG)对花生分离蛋白(PPI)进行改性,结果表明:加酶量、pH、反应温度、反应时间和底物蛋白浓度对PPI改性具有显著影响.通过单因素和正交实验得出凝胶性的最佳改性条件为:加酶量10U/g;最适pH7;反应温度50%;反应时间3h;反应底物浓度15%.改性后花生分离蛋白的凝胶性比对照提高了279%,溶解性和乳化性分别降低了44%和31%,乳化稳定性提高了8.5%.     

Modification of the nitrogen solubility properties of soy protein isolate following proteolysis and transglutaminase cross-linking

The effect of (a) limited hydrolysis [0.5–2.0% degree of hydrolysis (DH)] with Alcalase™, (b) cross-linking with transglutaminase (TGase) and (c) combinations of these modifications on the nitrogen solubility (pH 3–8) of soy protein isolate (SPI) was investigated. Between pH 3.0 and 5.0, SPI hydrolysates, hydrolysates of cross-linked SPI and the cross-linked products of SPI hydrolysates displayed significant (P<0.05) increases in solubility compared to unmodified SPI. Cross-linking pre- or post hydrolysis did not alter the overall trend of increased (P<0.05) solubility relative to the unmodified control at low pH. At 2% DH, cross-linking pre- or post-hydrolysis resulted in greater solubility (P<0.05) than that observed in hydrolysates per se at low pH. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS–PAGE) indicated that the 22 kDa 11S basic polypeptide was relatively resistant to Alcalase hydrolysis and that the 18 and 22 kDa 11S basic polypeptides were not susceptible to TGase cross-linking. The results demonstrate that a combination of enzymatic treatments and the order in which they are applied may have potential for creating novel food ingredients with improved functional properties, especially those properties that are dependant on high solubility at low pH.     

Preparation and functional properties of protein coprecipitate from sheep milk

The optimum conditions for the production of coprecipitate from sheep milk were studied. The best percentage of calcium chloride added to milk was 0.2%, which resulted in a recovery of 97.5% of milk proteins. At low pH (4.5–5), the recovery of protein was low, but it increased at higher pH values (5.5–6.5); recovery was greatest at pH 6.5. The optimum heating temperature to obtain coprecipitate from sheep milk was 85–95°C. The functional properties of the sheep milk coprecipitate were studied. At pH values higher than 6, there were no differences between the solubility of sheep milk coprecipitate and sheep milk sodium caseinate, but the solubility of coprecipitate at pH values lower than 5 was relatively higher than those of the caseinate. At pH ≥6, the emulsion activity index (EAI) for emulsions of sheep milk coprecipitate and caseinate increased as pH increased; at all pH values, the EAI of the coprecipitate was higher than that of the caseinate. Sheep milk coprecipitate showed higher foaming ability and stability than sheep milk sodium caseinate.     

转谷氨酰胺酶聚合改性大豆分离蛋白的功能特性研究

研究了转谷氨酰胺酶(MTGase)聚合改性大豆分离蛋白的持水性、吸油性、溶解性、乳化性、发泡性及凝胶强度等功能特性。结果显示,与大豆分离蛋白相比,MTGase改性的大豆分离蛋白(MSPI)具有更高的凝胶性和乳化稳定性,但其溶解性、持水性、吸油性、起泡性与泡沫稳定性和乳化性明显减弱。