Abstract: The glutelin from litchi juice was purified using the Osborne sequential protein extraction method, and its molecular mass distribution, thermal stability and secondary structures were analyzed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), differential scanning calorimetry (DSC) and infrared (IR) spectroscopy, respectively. The results showed that the glutelin had a large molecular mass and contained approximately 10 bands, most of which had a molecular mass of 50 kDa or above. After reduction, a few bands with higher molecular mass disappeared and new bands with smaller molecular mass (mostly including 50 kDa) appeared. The surface hydrophobicity was evaluated by SDS-binding capacity. The glutelin could bind (74.25 ± 5.26) μg of SDS per mg sample, and its contents of free sulphydryl group, total sulphydryl group and disulfide bond were (29.83 ± 1.72), (40.59 ± 2.04) and (5.38 ± 0.18) μmol/g, respectively. Its denaturation peak temperature was 105.24 ℃. The major secondary structures were β-sheet and β-turn, accounting for 33.92% and 64.7%, respectively. Hence, we can infer preliminarily that the composition of glutelin in litch juice is complex, mainly containing high-molecular-weight glutelins, which have strong surface hydrophobicity, low disulfide bond content and good thermal stability.

Key words: litchi juice, glutelin, SDS-PAGE, IR spectroscopy