Study On The Effect Of Sodium Trimetaphosphate On The Micro-structure And Application Properties Of Kudzu Starch

Kudzu, a nutrient-rich industrial crop product, is an important traditional Chinese herb. It is receiving increasing attention due to its widespread cultivation, high yield and healthy application. Starch, which has a series of special properties, is a main ingredient of kudzu. In this thesis, the structure and cross-linked reaction of kudzu starch were systematic studied so as to suggest some ideas for applications in food fields.The kudzu amylose(AM) and amylopectin(AP) were fractionated from kudzu starch by using n-butanol and isoamyl alcohol. The morphological features and micro-structure of two fractionated starches were investigated by scanning electronic measurement(SEM), X-ray diffraction(XRD) and Fourier transform infrared spectroscopy(FT-IR). Amylose and amylopectin showed variable in size and irregular aggregation. According to XRD patterns, amylopectin was amorphous and amylose was a superposition of the A and B type patterns. Using enzymolysis, chain structure of amylose and amylopectin molecule was analyzed. Amylose molecule had less average number of chains each molecule but longer average chain length compared with those of amylopectin molecule. At the same time, the solubility, swelling power and thermal property of kudzu native starch, AM, and AP were studied.Kudzu native starch was cross-linked in the presence of sodium trimetaphosphate(STMP)(5%, 10% and 12%) at the different temperature(35?, 45?, 55?) in 1h, 2h and 3h. The morphology, crystalline structure, molecular structure, retrogradation, freeze-thaw stability and thermal properties of cross-linked starches with different degrees of substitution were investigated systematically with the comparison with kudzu native starch. Then low cross-linking starch and high one were fractionated to study the structures and properties. The results showed that cross-linking reaction was came up in the crystalline region and crystalline structure of amylose was destroyed. The transmittance, solubility and swelling power were reduced, while freeze-thaw stability was improved with the addition of cross-linked bond. The research of structures and properties will be helpful for the process of food processing and storage and the control of starch modification.