The fifth basic taste—umami—is based on hydrophilic monosodium L-glutamate (L-Glu), and, to a smaller extent, on L-aspartate (L-Asp), which can be found in free form in seaweeds. The umami taste can be elicited by the synergistic effect of 5′-nucleotides, guanosine-5′-monophosphate (GMP), and inosine-5′-monophosphate (IMP). In this work, twelve edible seaweeds, two green (Codium tomentosum, Ulva rigida), six red (Chondracanthus teedei var. lusitanicus, Chondrus crispus, Gracilaria gracilis, Grateloupia turuturu, Nemalion helminthoides, Osmundea pinnatifida), and four brown (Bifurcaria bifurcata, Fucus vesiculosus, Saccorhiza polyschides, Undaria pinnatifida), from the Portuguese seashore, were selected for the analysis of umami amino acids and 5′-nucleotides. To determine the concentrations of umami free compounds, L-Glu, L-Asp, GMP, and IMP, the usual procedure for the preparation of seaweed’s broth was carried out, and the resulting extracts were analyzed by HPLC-DAD. The effect of the seaweed’s pretreatment, oven-dried and lyophilized, was also studied. Results showed that all seaweed species contained free amino acids in broad range, whereas umami 5′-nucleotides were not detected. The lyophilized C.crispus and G. gracilis contained the highest amounts of free L-Glu (627 ± 109 mg (100 g)⁻¹ and 398 ± 67 mg (100 g)⁻¹, respectively) and L-Asp (520 ± 102 mg (100 g)⁻¹ and 270 ± 10 mg (100 g)⁻¹, respectively). Two-factor PCA explained quantitatively (90%) the variance of seaweed species based on umami L-Glu content after different drying techniques applied. The results indicate that lyophilization constitutes a superior procedure for increasing the umami potential in most of the selected seaweeds.

第五种基本味道-鲜味-基于亲水性L-谷氨酸钠（L-Glu），并在较小程度上基于L-天冬氨酸（L-Asp），可以在海藻中以游离形式发现。鲜味可通过5'核苷酸，鸟苷5'-单磷酸（GMP）和肌苷5'-单磷酸（IMP）的协同作用引起。在这项工作中，十二食用海藻，两个绿色（刺松tomentosum，石莼杜松），六冲（Chondracanthus teedei变种lusitanicus，爱尔兰海藻，江蓠纤细，繁枝turuturu，Nemalion helminthoides，Osmundea菜），以及四个布朗（Bifurcaria bifurcata，墨角藻，Saccorhiza polyschides，裙带菜），来自葡萄牙海边，被选定为鲜味的氨基酸和5'-核苷酸的分析。为了确定不含鲜味的化合物，L-Glu，L-Asp，GMP和IMP的浓度，按照制备海藻肉汤的常规方法进行操作，然后用HPLC-DAD分析所得提取物。还研究了紫菜预处理，烘箱干燥和冻干的效果。结果显示，所有海藻种类均包含宽范围的游离氨基酸，而未检测到鲜味5'核苷酸。冻干的C. crispus和G. gracilis含有最高量的游离L-Glu（分别为627±109 mg（100 g）^-1和398±67 mg（100 g）^-1）和L-Asp（520±102 mg（100 g）^-1和分别为270±10 mg（100 g）^-1）。在采用不同的干燥技术后，基于鲜味L-Glu含量的两因素PCA定量解释了海藻种类的变化（占90％）。结果表明，冻干是增加大多数选定海藻鲜味潜力的优良方法。