基于V-型晶种竞争性干预重结晶过程的淀粉回生调控共性机制

Due to complexity of factors which affect retrogradation and limited studying methods, common theory of controlling retrogradation by emulsifiers and fatty acids is not fully understood and verified. Especially, the intervention process of V-type seed crystal for recrystallization is still unclear, which restricts the development of preparing rice & flour products with high quality. As a result, this project simplifies the retrogradation system by using V-type seed crystal as the real crystal system and by accurately controlling the addition of crystal. Furthermore, advanced techniques, including Atomic Force Microscopy with imaging system, Wide X-ray Diffraction with Jade 6.5, and Fluorescence Spectroscopy with fluorescent guest, will be developed and used for analysing the crystalline structure of starch. Based on these studies, we firstly try to find out the critical size of the V-type seed crystal which can act as crystal nucleus to affect retrogradation in heterogeneous phase. Secondly, we plan to propose the competitive intervention of V-type seed crystal for recrystallization based on the effect of V-type seed crystal on the mode of nucleus growth and transformation of crystal structures. These findings will will help to understand the common mechanism of controlling retrogradation induced by emulsifiers and fatty acids, providing scientific basis for preparation of starchy food products with high quality.

鉴于淀粉回生影响因素的复杂性和传统研究手段的局限性，回生调控共性理论长期以来拘泥于乳化剂类、脂肪酸类外源组分抑制回生作用表征与单一机制，缺乏晶核干预重结晶过程解析的实质性突破。特别是上述外源组分介入淀粉体系形成的V-型晶核是诱导V-型结晶增长还是竞争性干预B-型重结晶问题不明确，这也是开发高品质米面制品所面临的瓶颈。基于此，本项目提出在大米淀粉回生过程中，添加V-型晶种诱导淀粉重结晶过程，简化回生研究体系；建立并运用AFM轻敲模式下的晶粒成像分析、WXRD Jade 6.5晶胞参数解析、荧光客体分子介入荧光光谱的晶体密度测试等淀粉晶态解析的先进手段，考察三类V-型晶种的晶态结构特征，明确其作为淀粉V-型/B-型成核启动子的临界尺寸，从V-型/B-型晶粒成核模式、片晶层状结构转化等角度，解析V-型晶核竞争性干预重结晶途径，揭示外源组分抑制回生的共性机制，为高品质米面制品开发提供重要基础数据。

针对乳化剂类、脂肪酸类外源组分抑制回生的共性机制—V-型晶核是诱导V-型结晶增长还是竞争性干预B-型重结晶问题，本项目设计合成了替代传统有机溶剂的新型咪唑离子液，以此为反应环境，筛选并分别采用硬脂酰乳酸钠、单甘脂、蔗糖酯等客体分子与干热非晶化淀粉分子络合，制备出三类V-型晶种，以A-型、B-型晶种作为对照组，考察其晶态结构特征，发现V-型晶种呈现为正交晶系的V-型淀粉晶体，平均有效粒径200-318nm，作为晶核的临界尺寸为70-71nm；建立并利用Avrami模型，明晰了干预淀粉回生重结晶成核模式，V-型晶种诱导单螺旋结构形成，使淀粉重结晶成核指数n由0.72降低至0.68，竞争性干预B-型重结晶，从而促进V-型晶粒生长；明确了诱导淀粉回生重结晶片晶特征与晶胞参数转化规律，发现V-型晶种使回生淀粉片层厚度从11.02nm降低至10.36nm，a、b晶轴分别缩短至4.48、10.48Å，c轴增长至24.36Å，γ角由120°缩小到90°，晶体晶系为正交晶系，晶胞体积减小至1.14nm3，晶胞形态趋近于V-型晶种晶胞。上述成果系统揭示了乳化剂类、脂肪酸类外源组分抑制回生的共性机制，在Food Hydrocolloids、Starch/Starke等本领域国际主流刊物发表SCI论文4篇；运用相关理论开发多晶型抗性淀粉的制备方法、慢消化淀粉的制备方法等技术，获授权发明专利3件（其中美国、日本各1件），申请国家发明专利1件、国际PCT专利1件；执行期内培养硕士研究生3名；参加国内外学术研讨会议、软件模块培训、企业调研10人次。

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