Study On The Molecular Structure Of The Lotus-seed Starch And Its Applications

The molecular structure of lotus-seed starch and effects of different methods on its structure were studied in the paper. Three methods were considered that were ultrasonic, high pressure homogen and a-amylase limited-enzymolysis. And the mechanism of lotus-seed starch retrogradation and technologies to restrain it were studied. Therefore, an important recommendation for improving the quality of lotus-seed deep-processing products was offered.A conclusion was drew through the GPC(Gel Permeation Chromatography) that lotus-seed starch is composed of amylose(Am) and amylopectin(Ap). Lotus-seed starch has a high content of Am which was up to 42% in the total starch. And these were the main reason for lotus-seed starch retrogradation easier than others.Lotus-seed starch, Am and Ap exhibited that λ_max at I₂-KI blue color were 622nm, 631nm and 567nm respectively through UV-Visible absorption analysis. Therefore, date base for quick determination of the Am and Ap content in lotus-seed was offered.For Am and Ap in lotus-seed, blue values were 1.072 and 0.252. The former was in the normal range of Am blue value, but the latter was beyond the normal range of Ap blue value. It was indicated that anhydroglucose unit of outer chain in Ap crystal went beyond 30 and this was the other important reason for lotus-seed starch retrogradation.It was indicated by HPLC that the average molecular weight of lotus-seed starch, Am and Ap were 1.7 × 10⁶g/mol, 6.4 × 10⁵g/mol and 2.8 × 10⁶g/mol, respectively.Molecular structure of Ap in lotus-seed was analyzed by enzymolysis. It was indicated that there were 5 branched chains in Ap molecule which were A, B₁, B₂, B₃ and B₄(C), and then 2 chains in the main chain and 1～2 chains in every other branch chain. The branched degree of Ap in lotus-seed was lower. Degree of Polymerization (DP) of A, B₁, B₂, B₃ and B₄(C) were 8, 33, 53, 86 and 1116 respectively. It was showed that the fine structure of Ap in lotus-seed was very different from others and it might lead lotus-seed starch to retrograde easily.It was verified that ultrasonic, high pressure homogen and a-amylase limited-enzymolysis could inhibit the retrogradation of lotus-seed starch with high water content. The best result was obtained by a-amylase limited-enzymolysis, but excessive enzymolysis would destroy the flavour mass, so the enzymolysis rate would...