L-天门冬氨酸钠,又称氨基-L-丁二酸一钠、L-天门科氨酸钠(1水),英文名称为Sodium L-aspartate。它是一种氨基酸衍生物,广泛应用于食品和饲料添加剂中,通常呈现为无色至白色柱状结晶或白色结晶性粉末,味道清淡,味觉阈值0.16%,熔点140.4℃。这种物质易溶于水(20℃时溶解度为66.7%),但不溶于乙醇。天然存在于甜菜、乳蛋白等中。
应用作为一种大宗氨基酸产品,L-天门冬氨酸钠在医药、食品和化工等领域有广泛用途。在医药方面,它主要用于治疗心脏病、促进肝功能、氨解毒、疲劳消除以及氨基酸输液的主要成分;同时也是多种小分子药物(如L天冬氨酸盐、丙氨酸和天门冬酰胺)的合成原料。在食品工业中,它是良好的营养增补剂,可添加于各种清凉饮料中作为阿斯巴甜的主要生产原料。在化工方面,它可以用于制造合成树脂,大量用于合成环保材料聚天冬氨酸。此外,L-天门冬氨酸钠还被用作食品行业的保鲜剂、防腐剂,可代替味精;在医药行业中,则作为中间体。
鉴别试验取0.1%试样水溶液5ml,加入茚满三酮试液(TS-250)1ml加热3分钟后应呈现紫色。钠盐反应阳性(IT-28)。
含量分析准确称取预经过在盛有硅胶的干燥器中干燥5h后的试样0.1g,溶于0.5ml水中,立即加入甲酸3ml和冰醋酸100ml,再加α-萘酚苯试液(TS-153)0.5ml,用0.1mol/L高氯酸溶液滴定至绿色终点。同样进行空白试验。每毫升0.1mol/L高氯酸液相当于L-天门冬氨酸钠(C4H6NNaO4·H2O)8.655mg。
毒性GRAS(FEMA)级别。
使用限量日本(1998年):饮料0.1%~0.5%,甜味剂5.0%~15.0%,鱼糕0.1%~0.5%,红肠0.1%~0.3%,肉汁汤料0.5%~1.0%,咖喱乳酪面粉糊0.3%~0.5%,酱油0.1%~0.4%,醋0.5%~1.0%,五香紫菜调味液1.0%~2.0%,鱼罐头0.1%~0.5%。
化学性质L-天门冬氨酸钠为无色至白色柱状结晶或白色结晶性粉末,味道清淡,味觉阈值0.16%,熔点140.4℃。易溶于水(20℃时溶解度为66.7%),不溶于乙醇。天然存在于甜菜、乳蛋白等中。
生产方法L-天门冬氨酸钠通常通过氢氧化钠中和左旋天冬酸获得,也可由细菌发酵得到L-天门冬氨酸后加氢氧化钠中和结晶而得。
Aqueous solutions of L-glutamine, L-asparagine, sodium L-glutamate, sodium L-aspartate, L-serine, and L-threonine were γ-irradiated in the presence of a spin trap, 2-methyl-2-nitrosopropane. Stable spin adducts produced in the irradiated solutions were analyzed by the spin-trap hplc–esr method. The spin adducts of the following short-lived radicals were found and identified: H2NCOCH2CH2ĊHCOO− (1), [Formula: see text] and [Formula: see text] for L-glutamine; [Formula: see text] (2) for L-asparagine; −OOCCH2CH2ĊHCOO− (3) and [Formula: see text] for sodium L-glutamate; −OOCCH2ĊHCOO− (4) and [Formula: see text] (5) for sodium L-aspartate; [Formula: see text] and HOCH2ĊHCOO− (6) for L-serine; CH3CH(OH)ĊHCOO− (7) and [Formula: see text] for L-threonine. The free radicals, 1, 3, 4, 6, and 7, were due to the reaction of the hydrated electron [Formula: see text] with these amino acids and the other adducts were due to the attack of hydroxyl radical (•OH). The two diastereomeric pairs of spin adducts of the short-lived radicals, 2 and 5, could be individually separated by the technique utilized.