动态高压微射流协同糖基化处理对β-乳球蛋白热稳定性和结构的影响

Effects of dynamic high pressure microfluidization pretreatment combined with glycation on thermal stability and structure of β-lactoglobulin

采用动态高压微射流(dynamic high pressure microfluidization,DHPM)协同葡聚糖糖基化处理对β-乳球蛋白(β-lactoglobulin,β-Lg)进行改性,研究其热稳定性和结构的变化。结果表明,β-Lg的峰顶温度为73. 48℃,经DHPM不同压力(40、80、120 MPa)处理后,其热稳定性先下降后上升,但经DHPM协同糖基化处理后,其热稳定性均呈上升趋势。理化分析结果显示,80 MPa DHPM协同糖基化处理的β-Lg具有最低的游离氨基酸含量(2. 20 mg/m L)和最高的褐变程度(A294=1. 092,A420=0. 062),说明DHPM预处理可以促进β-Lg-葡聚糖的糖基化反应,且80 MPa为最佳处理压力。结构分析表明,DHPM处理可明显提高β-Lg的表面疏水性和自由巯基含量,降低其内源荧光强度,使其发生二级结构变化。经DHPM协同糖基化处理后,β-Lg的表面疏水性有所降低,但仍高于天然β-Lg的表面疏水;自由巯基含量呈现先降低后升高趋势,在80 MPa时明显高于天然β-Lg,内源荧光强度随着压力的增加呈先降低后上升的趋势,但均明显低于天然β-Lg的内源荧光强度。因此,DHPM 80 MPa预处理样品具有最高的热稳定性和糖基化程度,且β-Lg的糖基化程度越高,其热稳定性越好。

Effects of dynamic high pressure microfluidization(DHPM)pretreatment(0,40,80 and 120 MPa)combined with dextran glycation on thermal stability and structure ofβ-lactoglobulin(β-Lg)were investigated.The results showed that the peak temperature ofβ-Lg is 73.48℃,which decreased first and then increased after pretreated by DHPM at 40,80 and 120 MPa.However,the thermal stability was improved after DHPM pre-treatment combined with glycation.Physiochemical analysis revealed that glycatedβ-Lg pretreated with DHPM at 80 MPa gave the lowest free amino(2.20 mg/mL)and the highest browning degree(A 294=1.092,A 420=0.620),suggesting that DHPM pre-treatment can promote glycation ofβ-Lg and dextran,and 80 MPa is the best pressure.Structural analysis indicated that DHPM pre-treatment can obviously improve the surface hydrophobicity and free sulfhydryl groups content,reduce the intrinsic fluorescence intensity,and change the secondary structure ofβ-Lg.After DHPM pre-treatment and glycation,the surface hydrophobicity ofβ-Lg was significantly reduced,but still higher than that of naturalβ-Lg,the content of free sulfhydryl groups increased first and then decreased with pre-treatment pressure,β-Lg content in 80 MPa pre-treated group was much higher than that of naturalβ-Lg.The intrinsic fluorescence intensity showed an adverse change trend with free sulfhydryl groups,but it still much lower than that of naturalβ-Lg.Therefore,β-Lg pre-treated with 80 MPa has the highest thermal stability and glycation degree,and the higher the glycation degree ofβ-Lg resulted,the better thermal stability it will be.