酶辅助碱法提取龙眼核淀粉的结构与理化性质研究

目的:明确酶辅助碱法提取的龙眼核淀粉的结构及理化性质。方法:以龙眼核为原料，碱性蛋白酶为酶解剂提取龙眼核淀粉，研究了其化学组成、粒径、微观形貌、晶体结构、透明度、溶解度及膨润力、热力学特性及糊化特性等。结果:100 g龙眼核淀粉中含有82.64 g淀粉、0.68 g粗脂肪、0.46 g粗蛋白和1.06 g灰分，其直链淀粉含量为36.37%；其颗粒多呈椭圆形或不规则多边形，平均粒径为11.21 μm，结晶结构为A型，近程有序程度较高；1%（w/v）龙眼核淀粉糊的透光率为4%；溶解度和膨润力均随温度上升而增大，90 ℃时分别为11.26%和15.93%；龙眼核淀粉具有较高的糊化起始温度（70.4 ℃）、峰值温度（75.9 ℃）、结束温度（82.1 ℃）和糊化焓（13.7 J/g），其热糊稳定性较差，冷糊稳定性较好。结论:酶辅助碱法提取的龙眼核淀粉直链淀粉含量高，蛋白质含量下降明显，颗粒小，不易糊化。

Structural and Physicochemical Properties of Longan Kernel Starch by Enzyme-assisted Alkali Extraction

Objective: To clarify the structure and physicochemical properties of longan kernel starch extracted by enzyme-assisted alkali method. Methods: Using longan kernel as raw material and alkaline protease as enzymatic hydrolysis agent, the longan kernel starch was extracted. The chemical composition, particle size, morphology, crystal structure, transparency, solubility and swelling power, thermodynamic properties and gelatinizing properties of starch were studied. Results: 100 g longan kernel starch contained 82.64 g starch, 0.68 g crude fat, 0.46 g crude protein and 1.06 g ash, and its amylose content was 36.37%. Its particles were mostly elliptic or irregular polygon, and their average size was 11.21 μm. The starch had type A crystalline structure and higher short-range order degree. In addition, 1% (w/v) longan kernel starch paste had 4% transparency. Its solubility and swelling power increased with the increase of temperature, being 11.26% and 15.93% at 90 ℃, respectively. Longan kernel starch had high gelatinization initial temperature (70.4 ℃), peak temperature (75.9 ℃), conclusion temperature (82.1 ℃) and enthalpy change (13.7 J/g). Its hot paste stability was poor while its cold paste stability was better. Conclusion: Longan kernel starch by enzyme-assisted alkali extraction had high amylose content and its protein content decreased obviously. In addition, it had small granules, and it was not easily gelatinized.