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蜡质玉米淀粉凝胶的冻融稳定性
引用本文:宁吉英,顾丰颖,高萍萍,曹晶晶,罗其琪,王锋.蜡质玉米淀粉凝胶的冻融稳定性[J].中国农业科学,2017,50(8):1514-1524.
作者姓名:宁吉英  顾丰颖  高萍萍  曹晶晶  罗其琪  王锋
基金项目:国家农业科技创新工程项目、中央级公益性科研院所基本科研业务费专项(2015ZL050)
摘    要:【目的】采用多次冻融循环(FTC)处理手段,研究蜡质玉米淀粉凝胶与冻融稳定性相关的物性变化,为蜡质玉米淀粉在冷冻食品中的推广应用提供科学支撑。【方法】以一个普通玉米淀粉样品(YM)为对照、两个蜡质玉米淀粉样品(WCS1、WCS2)为研究对象,采用离心过滤方法测定淀粉凝胶的析水率;差示扫描量热仪(DSC)测定淀粉凝胶的糊化焓、回生焓、冰晶熔化焓;Brabende黏度仪测定淀粉凝胶的糊化特性;物性测试仪测定蜡质玉米淀粉凝胶的质构特性;流变仪测定淀粉凝胶的凝胶动态黏弹性;扫描电子显微镜(SEM)观察淀粉凝胶截面的微观结构。【结果】析水率测定结果显示首次FTC后,WCS表现超强持水能力,其中WCS2持水能力最强,析水率为5.75%,而YM持水能力最弱,析水率超过50%。随着冻融循环次数的增加,淀粉凝胶的回生率和冰晶熔化焓均逐渐增大,且1、3、5次FTCs之间差异显著,说明多次冻融使淀粉的回生程度和可冻结水含量增加。WCS的回生率在首次FTC时达到17%—18%,而YM的在40%—50%。WCS的冰晶熔化焓在首次FTC时达到540 J·g~(-1)左右,而YM的在555 J·g~(-1)左右。5次FTCs后淀粉凝胶硬度均发生明显的增大,其中WCS凝胶硬度较小(45—100 g),远低于YM淀粉凝胶硬度(440 g左右)。凝胶动态黏弹性结果显示随着冻融次数的增加,淀粉凝胶的tanδ均逐渐降低,但WCS的tanδ值始终大于YM的,表明WSC凝胶较黏软。WCS的糊化特性也表明其在冷却过程中不易老化。5次FTCs后的淀粉凝胶结构均发生明显变化,WCS凝胶形成的网络结构较不规则,淀粉壁出现的孔道不明显且相互黏连缠绕;YM凝胶形成比较致密的网络状结构,结构较规则,淀粉壁出现的孔道完整,淀粉壁光滑。【结论】蜡质玉米淀粉凝胶经冻融处理后,其抵抗由温度波动造成的不良物理变化的能力强,比普通玉米淀粉凝胶的冻融稳定性好,本研究结果对蜡质玉米淀粉在冷冻食品中的应用具有重要参考价值。

关 键 词:蜡质玉米淀粉  冻融稳定性  析水率  凝胶动态黏弹性  微观结构  />
收稿时间:2016-08-04

Freeze-Thaw Stability of Waxy Corn Starch Gel
NING JiYing,GU FengYing,GAO PingPing,CAO JingJing,LUO QiQi,WANG Feng.Freeze-Thaw Stability of Waxy Corn Starch Gel[J].Scientia Agricultura Sinica,2017,50(8):1514-1524.
Authors:NING JiYing  GU FengYing  GAO PingPing  CAO JingJing  LUO QiQi  WANG Feng
Affiliation:Institute of Agro-products Processing Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-Products Processing, Ministry of Agriculture, Beijing 100193
Abstract:【Objective】The objective of this study was to research on the changes of the physical properties of waxy corn starch gel by multiple freeze-thaw cycles (FTC), which has relation with freeze-thaw stability. Results of his research will provide scientific supports for popularization and application of waxy corn starch in frozen foods. 【Method】 An ordinary corn starch samples (YM) and two waxy corn starch samples (WCS) were taken as the control and research materials, respectively. The syneresis of starch gels was determined by centrifugation-filtration. The gelatinization enthalpy, retrogradation enthalpy, and ice melting enthalpy of starch gels were determined by DSC. The pasting properties of starches were determined by Brabender Viscograph. The texture of starch gels were determined by Texture Analyser. The dynamic rheological properties of starch gels were determined by dynamic rheometer. The microstructure of starch gels were observed by SEM.【Result】The result of syneresis rate showed that after the first FTC, WCS displayed ultra-strong ability of holding water. WCS2 had the strongest ability to hold water, and the syneresis rate was 5.75%. However, YM had the weakest ability to hold water, and the syneresis rate was more than 50%. The results of the retrogradation rate and ice melting enthalpy showed that they gradually increased with the increase of freeze-thaw cycles. And there was a significant difference in the retrogradation rate and ice melting enthalpy among 1, 3, and 5 FTCs, which showed the retrogradation degree and freezable water increased because of multiply freeze-thaw cycles. After the first FTC, the retrogradation rate of WCS and YM were 17%-18% and 40%-50%, respectively. And after the first FTC, ice melting enthalpy of WCS and YM was about 540 J·g-1 and 555 J·g-1, respectively. The result of hardness showed that the hardness of starch gels increased obviously after five FTCs, and the hardness of WCS and YM was 45-100 g and 440 g, respectively. The result of dynamic rheological properties showed that tanδ of starch gels gradually decreased with the increase of freeze-thaw cycles. However, tanδ of WCS was always higher than tanδ of YM, which showed WCS gels were softer and more sticky. The result of pasting properties showed that WCS was not easy to aging in the process of cooling. The result of microstructure showed that the structure of starch gels changed obviously after five FTCs. The matrix surrounding pores of WCS gels were thin and atypical. However, the matrix surrounding pores of YM gel were thick and typical.【Conclusion】The ability of WCS gels resisting undesirable physical changes caused by temperature fluctuations is strong when WCS gels undergone FTC treatment. And its freeze-thaw stability is better than YM gel. This research has important reference values for application of waxy corn starch in frozen foods.
Keywords:waxy corn starch  freeze-thaw stability  syneresis rate  dynamic rheological properties  microstructure
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