焙烤体系中膳食纤维非酶褐变影响机制解析

In order to improve the daily intake of dietary fibre, bakery products have been fortified with dietary fibre in recent years. The baking conditions such as high temperature and low water content are suitable for the non-enzymatic browning. Thus, the fact that the color of bakery products become darker when dietary fibre is added has become widely accepted. However, the color of baked commodities is pale when the resistant starch is added. Due to the complexity of thermal decomposition of dietary fibre and non-enzymatic browning reaction, the influences of chemical composition and structure of dietary fibre on the color of bakery products are still unclear. Based on the previous research, the effects of water content, baking temperature and baking time on the color of bakery products in the presence of dietary fibre will be investigated. In order to study the influences of composition and structure of dietary fibre on the color due to Maillard reaction, the degradation pathway of dietary fibre alongside the Maillard reaction involving dietary fibre and wheat protein will be studied. Besides, the degradation behavior and caramelization of dietary fibre will be analyzed to establish the relationship of the color of caramelization with the composition of dietary fibre. The project is expected to provide clear mechanisms by which different dietary fiber in bakery products function to provide the characteristic color by enzymatic browning. Moreover, the theoretical basis for application of dietary fibre in bakery products will be elucidated.

在焙烤食品中添加膳食纤维以提高人日摄入量是近年来的研究热点之一。鉴于焙烤体系的高温、低水分是非酶褐变的适宜条件，膳食纤维添加会带来颜色的加深是被广泛接受的预期，然而抗性淀粉的添加却截然相反。鉴于膳食纤维热降解行为的复杂性以及非酶褐变自身的复杂性，人们目前还未能从组成、结构层面确定不同来源膳食纤维对焙烤食品色泽影响差异的确切机制。基于申请人前期的研究基础，本项目首先阐明了水分含量、焙烤温度和焙烤时间等因素对膳食纤维在焙烤体系中非酶褐变的影响规律；通过对膳食纤维热降解途径以及膳食纤维与小麦蛋白Maillard褐变的研究，揭示膳食纤维的来源、组成对其Maillard非酶褐变影响的化学机制；通过对膳食纤维热降解特性以及膳食纤维焦糖化褐变规律的研究，建立膳食纤维焦糖化褐变与其化学组成的内在联系。本项目有望明确不同膳食纤维在焙烤食品中发生非酶褐变形成不同色泽的化学机制，为在焙烤食品中应用提供理论依据。

本研究以面包作为IDF的载体，分析了IDF的添加对面包品质及面团特性的影响，建立了面包品质和面团特性之间的联系，并探究IDF对小麦粉中面筋蛋白和小麦淀粉的影响，以期对IDF在面包中的合理应用发挥指导作用。主要研究内容和结果如下：.首先，本研究选取了六种来源于谷类、豆类、果蔬类的不溶性膳食纤维，测定了基本成分及理化性质，考察了不同种膳食纤维的添加对面包比容、色泽、质构、孔隙的影响及一周内面包硬度和水分含量的变化。结果表明：不同来源的IDF的化学组成存在显著差异，该差异直接影响了IDF的理化性质。添加了10%的IDF于面包中，比容减小，硬度变大，气孔变得大而稀疏，面包品质整体下降。不同组面包相比，添加小麦纤维的面包品质与空白组最为接近，比容下降了0.59 mL/g，硬度增加了219.13 g，而对柑橘纤维组面包品质影响最大，比容下降了1.55 mL/g，硬度增加了513.73 g。储藏期间面包芯硬度和水分变化结果表明，面包中添加膳食纤维可以延缓面包品质的劣化，其中添加果蔬类面包的硬化速率相对较低，水分减少速率最慢。初步研究发现，IDF的理化性质与面包品质存在相关性。.其次，研究IDF的添加对小麦粉粉质特性以及面团拉伸特性、发酵流变特性、微观结构等的影响，建立膳食纤维基本属性和面团性质，以及面包品质和面团性质的联系。结果表明：IDF的添加提高了小麦粉的吸水率、面团形成时间和弱化度，降低了面团的稳定时间、拉伸特性和发酵特性，且添加不同IDF组面团性质变化与面包品质变化趋势一致，添加柑橘纤维的面团湿面筋含量为24.95%，稳定时间仅5 min，即面筋稀释严重，相应的面包也呈现了较差的品质，可见面团性质既受到原料粉理化特性的影响，又会对面包品质产生影响。.最后，提取小麦粉中面筋蛋白和小麦淀粉，探究IDF对面筋蛋白和IDF对小麦淀粉两者之间的相互影响，结果表明：IDF的高吸水率和膨胀率导致面筋蛋白中的二硫键含量显著降低，添加柑橘纤维面筋蛋白的二硫键含量最低为19.64%，相较于空白组下降了7.21%，破坏了面筋网络结构，从而导致面包和面团性质存在较大差异，这说明IDF对面筋蛋白的作用，是影响面团流变学特性的关键因素，但IDF基本特性与小麦淀粉之间的相关性不明显。