低乳糖牛乳粉品质分析及蛋白特性研究

Quality analysis and protein characteristics of low lactose milk powder

为获得品质优良的低乳糖牛乳粉,该试验以生牛乳为原料,分别使用3种不同乳糖酶水解牛乳,对水解后的牛乳进行喷雾干燥得到了低乳糖牛乳粉-乳糖酶A(low lactose milk powder-enzyme A,LLMP-EA)、低乳糖牛乳粉-乳糖酶B(low lactose milk powder-enzyme B,LLMP-EB)、低乳糖牛乳粉-乳糖酶C(low lactose milk powder-enzyme c,LLMP-EC),测定其理化指标和游离巯基等蛋白特性。结果表明,LLMP-EA、LLMP-EB和LLMP-EC的外观及组织状态相近、色泽偏白,LLMP-EA的水分活度比LLMP-EB、LLMP-EC分别低6.29%、4.07%(P<0.05);LLMP-EA的水分含量比LLMP-EB、LLMP-EC分别低6.13%、3.32%(P<0.05);LLMP-EA多分散性指数(polydispersity index,PDI)值为0.13,LLMP-EA、LLMP-EB和LLMP-EC的Zeta电位无显著性差异(P>0.05);通过扫描电镜(scanning electron microscope,SEM)观察发现,LLMP-EA乳粉颗粒较为饱满、表面光滑、有轻微凹陷、颗粒聚集程度较低;LLMP-EA的游离巯基含量比LLMP-EB、LLMP-EC分别低19.90%、12.15%(P<0.05),而LLMP-EA表面疏水性比LLMP-EB低12.29%(P<0.05);LLMP-EA的α-螺旋结构分别比LLMP-EB、LLMP-EC高1.35%、1.94%(P<0.05)。因此,LLMP-EA的水分含量和水分活度低、PDI值仅为0.13,品质最佳;游离巯基含量和溴酚蓝结合量低、α-螺旋含量高,蛋白特性较好。

To obtain low lactose milk powder with good quality,this experiment used raw milk as raw material,hydrolyzed milk with three different lactase,and dried the hydrolyzed milk with spray to obtain low lactose milk powder lactase enzyme a(LLMP-EA),low lactose milk powder lactase enzyme b(LLMP-EB),and low lactose milk lactase enzyme c(LLMP-EC),and determined its physicochemical indicators and protein characteristics such as free thiol groups.Results showed that the appearance and organizational state of LLMP-EA,LLMP-EB,and LLMP-EC were similar,with a slightly white color,the water activity of LLMP-EA were 6.29%and 4.07%lower than that of LLMP-EB and LLMP-EC,respectively(P<0.05).The water contents of LLMP-EA were 6.13%and 3.32%lower than that of LLMP-EB and LLMP-EC,respectively(P<0.05).The polydispersity index(PDI)value of LLMP-EA was 0.13,and there was no significant difference in the Zeta potential of LLMP-EA,LLMP-EB,and LLMP-EC(P>0.05).Through SEM observation,it was found that LLMP-EA milk powder particles were relatively plump,with a smooth surface,slight depressions,and a low degree of particle aggregation.The free sulfhydryl contents of LLMP-EA were 24.81%and 13.80%lower than that of LLMP-EB and LLMP-EC,respectively(P<0.05),while the surface hydrophobicity of LLMP-EA was 14.02%lower than that of LLMP-EB(P<0.05),LLMP-EA’sα-helix structure were 1.33%and 1.90%higher than LLMP-EB and LLMP-EC,respectively(P<0.05).Therefore,LLMP-EA had low water contents and activity,and a PDI value of only 0.13,indicating the best quality.LLMP-EA had low free sulfhydryl contents and bromophenol blue binding capacity and highα-helix contents,indicating good protein properties.