支链淀粉聚合度对菠萝蜜种子淀粉老化性质的影响机理

Starch retrogradation is of great interest since the foods made of starch inevitably happen to retrograde after pasting and storage when the amorphous starches recrystallize, which results in the undesirable taste and texture qualities. In our previous work, it was found that correlation existed between retrogradation properties and particle size of jackfruit seed starch (JFSS). However, the effect of amylopectin polymerization on the retrogradation properties has not yet been reported. The relationship between retrogradation properties and structure need to be further investigated. Therefore, the different jackfruit cultivars were chosen as material, the amylopectin with different degree of polymerization will be extracted and its effect on retrogradation properties and molecule or fine structure of JFSS will be investigated when amylose was used as nuclei of recrystallization, including detecting and comparing the differentiation of retrogradation properties (nucleation ways, degree of retrogradation, rate of retrogradation, crystallization properties, microstructure, texture properties, freezing-thawing stability); the molecule and fine structure of JFSS will be investigated including expressing and analyzing molecule structure (cubic and polarized structure, size distribution, crystal type, crystallinity, crystallized and amorphous short-range molecular order, double helix structure, radius of gyration and hydrodynamic radius) and fine structure (molecular weight, chain length distribution, weight average molecular mass, number average molecular mass). The retrogradation model of the relationship among the properties changes induced by the amylopectin polymerization will be established between retrogradation properties and molecule or fine structure of JFSS, which can be used to interpret the relationship between retrogradation properties and molecule or fine structure of JFSS based on different degree of amylopectin polymerization. Those studies can provide the theoretical principle for the correlation between degree of amylopectin polymerization and retrogradation properties of JFSS.

淀粉质食品糊化后在贮藏过程中无定型淀粉分子发生重结晶的老化过程导致其口感、质构变差一直是科学家研究的热点问题。本项目前期研究表明菠萝蜜种子淀粉（JFSS）的老化性质与颗粒尺寸密切相关，然而支链淀粉聚合度对淀粉老化性质的影响研究未见报道，淀粉老化性质与结构之间的关系有待进一步深入研究。由此，本项目拟以不同聚合度的支链淀粉和不同品种JFSS直链淀粉为研究对象，以老化淀粉体系老化重结晶成核方式、老化程度、老化速率、晶体性质、微观形貌、冻融稳定性、分子结构和精细结构为考察指标，研究不同聚合度的支链淀粉在直链淀粉作为支链淀粉老化晶核或形成凝胶网络结构的方式对菠萝蜜种子淀粉老化过程的影响，建立支链淀粉聚合度影响JFSS老化的理论模型，揭示不同聚合度支链淀粉的JFSS分子结构和精细结构与老化性质间的关系，为解析支链淀粉聚合度对菠萝蜜种子淀粉的老化性质的影响机理提供理论参考。

淀粉质食品糊化后在贮藏过程中无定型淀粉分子发生重结晶的老化过程导致其口感、质构变差一直是科学家研究的热点问题。然而支链淀粉聚合度对淀粉老化性质的影响研究未见报道。本项目对13个新品种菠萝蜜种子淀粉（JFSS）开展功能特性研究，所有淀粉都具有高直链淀粉含量（26.56～38.34%）。JFSS微观形貌从三角形和四角形、圆形到半椭圆形/钟形变化，并且显示出颗粒尺寸变化（5.53～14.46 μm）。马来西亚8号和珍珠品种可应用在食品增稠剂或胶凝剂，马来西亚2号、3号和4号可应用于糯性食品，香饮所11号、4号、3号和2号比较适合于糖果或断奶食品的填料。通过开展不同菠萝蜜品种JFSS的分子结构和精细结构研究，结果表明JFSS的分子量和旋转半径范围分别为1.74×107g/mol ～4.61×107g/mol和115.4 nm ～144.2 nm。JFSS的分子量和旋转半径与大米淀粉、马铃薯淀粉相似，比玉米淀粉和糯米淀粉高。JFSS具有更高比例的A和B1链比例，却具有较低比例B2和B3+链比例，这些链长比例分别为38.33%～33.89%，39.06%～39.58%，17.13%～18.43%，4.96%～8.62%和18.27～19.71。M1’具有最低程度的支链淀粉聚合度（189506），而BD’具有最高支链淀粉聚合度（431481）。五个RJFSS样品显示出微观结构的显著变化，并且从紧凑结构（M1'）到松散结构（BD'）变化。增加支链淀粉聚合度导致五个RJFSS样品的再结晶速率从0.14（M1'）降低到0.10（BD'），并且Avrami指数从0.77（M1'）增加到0.96（BD'）。高脱水收缩（58.24～75.39%）形成致密结构（M1'），低脱水收缩（55.16～67.14%）形成松散结构（BD'）。随着支链淀粉聚合度的增加，5种RJFSS样品的回生焓、回生度、相对结晶度和吸光度比从10.92 J/g、68.16%、11.58%和0.55（M1'）降至7.03 J/g、56.33%、7.29%和0.49（BD'）。然而，转变温度分别从51.84℃、60.83℃和71.43℃（M1'）升至57.16℃、65.49℃和74.83℃（BD'）。所有结果表明，支链淀粉聚合度是一个重要的结构因素，可以显著影响淀粉在贮藏过程中的老化行为。