采用碱溶酸沉的方法提取南极磷虾分离蛋白(krill protein isolate,KPI),通过喷雾干燥和冷冻干燥的方式制备南极磷虾分离蛋白粉,并对这两种分离蛋白粉的结构及功能特性进行比较分析.结果表明:与冷冻干燥南极磷虾分离蛋白(freeze-dried krill protein isolate,FKPI)相比,喷雾干燥南极磷虾分离蛋白(spray-dried krill protein isolate,SKPI)明度大,色泽较好;扫描电子显微镜结果显示,SKPI呈现出向内凹陷的不规则球状结构,而FKPI为薄层片状结构,SKPI的堆积密度高于FKPI;圆二色谱进一步表明,与KPI相比,SKPI和FKPI均呈现α-螺旋含量下降、β-转角含量增加的趋势,其中,SKPI的α-螺旋含量下降27.9%,β-转角含量增加12.2%,表明喷雾干燥后蛋白质的二级结构均从有规则的结构向无规则的结构转化;SKPI持水力、持油力、乳化稳定性和起泡性等均高于FKPI,而SKPI的溶解性、乳化性却比FKPI的差.可见,不同的干燥方式会改变南极磷虾分离蛋白的结构特性,并进一步影响其功能特性.
Effects of Different Drying Methods on the Structure and Functional Characteristics of Isolated Proteins from Euphausia superba
The krill protein isolate(KPI)was extracted by alkali solution and acid precipitation,and the KPI powder was prepared by spray drying and freeze drying.Compared with the freeze-dried krill protein iso-late(FKPI),the spray-dried krill protein isolate(SKPI)had higher brightness and better color.The results of scanning electron microscopy showed that SKPI exhibited an irregular spherical structure with inward concavi-ty,while FKPI exhibited a thin layer sheet-like structure,and the former having a higher packing density than the latter.Circular dichroism further showed that both SKPI and FKPI showed a decreased α-helix content and increased β-turn content compared with KPI.The α-helix content of SKPI decreased by 27.9%,β-turn content increased by 12.2%,indicating that the secondary structure of the protein was transformed from regular struc-ture to irregular structure after spray drying.SKPI had higher water and oil holding capacity,emulsifying stabil-ity,and foaming ability than FKPI,while the former had poorer solubility and emulsifying ability than the lat-ter.Therefore,different drying methods will change the structural characteristics of KPI and further affect its functional characteristics.
krill protein isolatealkali solution and acid precipitationspray dryingfreeze dryingphysical and chemical propertiesfunctional characteristics
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