冻融循环次数对超声改性玉米淀粉凝胶特性和结构的影响

Effect of Number of Freeze-Thaw Cycles on the Properties and Structure of Ultrasonically Modified Corn Starch Gel

探讨经超声处理的玉米淀粉在冻融循环过程中其凝胶特性和结构的变化,以期为提升速冻淀粉基食品品质提供理论指导。利用流变仪、物性分析仪、低场强核磁共振仪、傅里叶变换红外光谱仪及X射线衍射仪,分析冻融循环次数对超声改性玉米淀粉凝胶动态流变学和质构特性的影响,并对其结构进行表征。结果表明:不同冻融循环次数下,以天然玉米淀粉作对照,超声改性玉米淀粉凝胶的析水率在第4次冻融时显著下降了5.19%(P<0.05),提高了冻融稳定性;超声改性玉米淀粉凝胶的储能模量和损耗模量降低,凝胶强度变弱;硬度在第4次冻融时显著降低了10.83%(P<0.05),直链淀粉含量下降了0.15%;超声改性玉米淀粉凝胶的碘结合力减弱,横向弛豫时间分布曲线整体左移,短程有序结构减弱,相对结晶度降低。综合凝胶特性和结构表征结果,表明超声处理能够抑制冻融循环过程中玉米淀粉凝胶体系中的水分迁移和双螺旋结构的形成,改善其冻融稳定性。

We investigated the changes of gel characteristics and structure of ultrasonically treated corn starch during freeze-thaw cycles,with a view to providing theoretical guidance for improving the quality of quick-frozen starch-based foods.The effects of the number of freeze-thaw cycles on the dynamic rheological and textural properties of ultrasonically modified corn starch gels were analyzed and their structures were characterized by using a rheometer,a texture analyzer,a low-field nuclear magnetic resonance(NMR)spectrometer,a Fourier transform infrared(FTIR)spectrometer and an X-ray diffractometer(XRD).The results showed that compared with native corn starch,the water separation rate of ultrasonically modified corn starch gels significantly decreased by 5.19%(P<0.05)at the 4th freeze-thaw cycle,indicating improved freeze-thaw stability;the storage modulus and loss modulus of ultrasonically modified corn starch gels decreased,and the gel strength was weaker;the hardness significantly decreased by 10.83%(P<0.05),and the amylose content decreased 0.15%.Moreover,the iodine binding force was weakened,the transverse relaxation time distribution curve was shifted to the left,the short-range ordered structure was weakened,and the relative crystallinity was reduced.The gel properties and the structural characterization results indicate that ultrasonic treatment can inhibit water migration and double helix structure formation in the corn starch gel system during freeze-thaw cycles and consequently improve its freeze-thaw stability.