酱油中鲜味二肽的分离鉴定及其呈味特性研究

Isolation, Identification and Taste Characteristics of Umami Dipeptides from Soy Sauce

为了明确酱油中鲜味肽的结构序列,本文对酱油中鲜味肽进行分离鉴定,并系统地研究了其呈味特性。酱油经超滤膜(膜通量:5 ku、3 ku和1 ku)分离获得4个组分(F1,F2,F3和F4),通过感官评定筛选出鲜味最强的组分F4(<1 ku)。该组分通过Sephadex G-15凝胶层析色谱继续分离得到8个组分(P1、P2、P3、P4、P5、P6、P7和P8),经感官评定筛选出鲜味最强的组分P2。采用超高压液相色谱串联质谱技术对P2组分进行多肽结构鉴定,通过手动De novo测序得到4条新的鲜味肽,其序列分别是Asn-Pro(230.1135 u)、Ala-His(227.1026 u)、Gly-Pro(173.0929 u)和Gly-Leu(189.1230 u)。然后采用固相合成技术合成四条肽并通过感官评定和电子舌分析,结果表明四条肽均具有明显的鲜味或鲜味增强作用。进一步研究发现,酱油的鲜味不仅来自于谷氨酸和天冬氨酸等鲜味氨基酸,小分子肽类也是构成酱油鲜味的重要成分之一。

In order to determine the structural sequence of the umami peptides in soy sauce,umami peptides were isolated and identified for systematic study on their taste characteristics.Four fractions(F1,F2,F3 and F4)were obtained through membrane ultrafiltration(membrane flux:5 ku,3 ku and 1 ku),with F4(<1 ku)having the strongest umami taste based on sensory evaluation.F4 was then selected for further separation by Sephadex G-15 gel chromatography to generate eight sub-fractions(P1,P2,P3,P4,P5,P6,P7 and P8).Among which,P2 exhibited the strongest umami taste in sensory analysis.P2 was analyzed by ultra-high pressure liquid chromatography-tandem mass spectrometry.Four new umami peptides were identified through De novo sequencing.They were all dipeptides with sequences as Asn-Pro(230.1135 u),Ala-His(227.1026 u),Gly-Pro(173.0929 u)and Gly-Leu(189.1230 u),respectively.Then,four peptides were synthesized by solid-phase peptide synthesis and analyzed by sensory evaluation and electronic tongue analysis.The obtained results showed that all the four synthesized peptides had distinct umami taste or umami-enhancing effect.Further studies showed that the umami taste of soy sauce was not only derived from umami amino acids such as glutamic acid and aspartic acid,but also from certain small peptides(which were important contributors to the umami taste of soy sauce).