Determination Of Dietary Fiber

Dietary fiber is regarded as the seventh human nutriment and has been the research target from last century. Dietary fiber has positive physiological functions for human and has been recognized by people. The determination of contents of dietary fiber is also important for the reason that too little or too much dietary fiber consumption will do harm to people.The thesis contains five chapters as following:In chapter one, the definitions, physiological functions and analytic methods of dietary fiber are reviewed.Characteristics of structures and of physiological functions of dietary fiber are introduced. The development and application of typical analytical methods of dietary fiber are also discussed, as well as the status of application and development.In chapter two, the enzyme-gravimetric method was used to determine the soluble, insoluble and total dietary fiber in food products. The results of the experiments show that the method is suitable for the determination of total dietary fiber in most products and is suitable for the determination of soluble and insoluble dietary fiber in some products.In chapter three, a simple and fast analytical method for determination of polydextrose was developed based on the phenol-sulphate acid spectroscopy. The conditions for determination of polydextrose were optimized by the orthogonal test. Results show that the method is accurate and reproducible, which is suitable for the analysis of the soluble dietary fiber——polydextrose content in food.Chapter four developed a HPLC method for the determination of polydextrose content and molecular weight.The HPLC was run on an Ultrahydrogel 250 column(7.8×300mm) with refractive index(RI) detector for determinations of content and average molecular weight of polydextrose in some samples. Distilled water was used as the mobile phase at a flow rate of 0.5ml/min. The correlation equation was established between molecular weight and retention time and applied to estimate the molecular weight of polydextrose samples. The calibration curve was linear over the polydextrose concentration range of 0.199～3.98mg/ml, with a correlation coefficient of r =0.9998. The polydextrose mass recovery ranged from 103% to 110% with a RSD of 1.91%. The method is found to be simple, reproducible and reliable, and thus ideally suitable for the analysis of polydextrose in food product.In chapter five, the soluble, insoluble and total dietary fiber of oats and oats products were determined by the enzyme- gravimetric method and the molecular weight of soluble dietary fiber in oats were also determined by the HPLC. Although oats in different regions have different contents of dietary fiber, oats are on the whole rich of dietary fiber. Oats products have less dietary fiber than oats because of adding other nutrient, which make them much more delicious.