【作者】 李艳芳；

【导师】 张京芳；

【作者基本信息】 西北农林科技大学 ， 林学， 2023， 硕士

【摘要】 香椿(Toona sinensis)属楝科香椿属植物,风味独特,有“树上佳蔬”的美称。香椿在全国18个省份均有种植,已发展成“富民工程”现代特色农业产业。然而,香椿的苦味影响消费者对其的满意度和可接受性,制约了香椿产业的发展。目前对香椿的研究主要集中在挥发性化合物、生物活性等方面,其苦味物质方面的报道甚少。基于此,本文拟对香椿苦味及其各类潜在苦味物质进行分析,明确主要苦味物质类型,解析其中关键苦味物质,并探讨降苦方法。主要研究结果如下:(1)不同产地及不同采摘期香椿感官评价结果表明,不同产地香椿样品苦味强度存在差异,总体呈现由北向南递增趋势,其中云南红油椿苦味值最高(4.80);安康青油椿和红油椿的苦味值总体呈现为随采摘期推后呈上升趋势。香椿苦味值与各类潜在苦味物质含量相关性分析表明,不同产地及不同采摘期香椿中总酚及总黄酮含量均与苦味值呈显著正相关,初步判断酚类和黄酮类是香椿苦味形成相关的重要化合物类型。(2)基于非靶代谢组学分析,在云南红油椿、重庆红油椿和宁夏红油椿两两之间共筛选到2532种差异代谢物。在识别到的各类差异代谢物基础上,依托公共苦味物质数据库和相关参考文献,共筛选出52种苦味代谢物,包括12种氨基酸、22种(类)黄酮、6种多酚、8种生物碱和4种皂苷;进一步以苦味值为因变量,采用偏最小二乘回归分析筛选到11种关键差异代谢物,其中7种为黄酮类物质,分别是黄芩素、山奈酚、异槲皮苷、木犀草素、桑黄素、槲皮素和紫云英苷。分析筛选到的苦味物质数量、苦味物质的丰度及其在组间的差异,发现黄酮类物质是香椿主要潜在苦味物质。(3)依据感官评价指导,通过乙醇提取、乙酸乙酯萃取及柱层析有效实现了云南红油椿中苦味物质的分离,获得了纯度较高的黄酮类苦味组分。对乙酸乙酯萃取组分中苦味活性最高的两个组分F-IV-13和F-IV-14采用UPLC-MS/MS进行分析,共鉴定到24个黄酮类苦味物质。这些苦味物质包含了非靶代谢组学分析中筛选到对香椿苦味差异贡献较大的5种黄酮类关键差异代谢物(山奈酚、异槲皮苷、木犀草素、槲皮素和紫云英苷)。(4)采用烫漂、超声、盐浸和盐浸后烫漂对云南红油椿进行降苦处理,结果表明盐浸后烫漂处理和烫漂处理均能显著降低香椿苦味。定量分析未经降苦处理及不同降苦处理香椿中9种黄酮苦味物质,发现异槲皮苷、紫云英苷、槲皮素、山奈酚和木犀草素均含量较高且与苦味值呈显著正相关,验证了这5种黄酮为香椿中的关键苦味物质。综合比较色泽、苦味值、苦味物质及挥发性成分等含量变化,烫漂处理降苦效果较好。综上所述,香椿中含有氨基酸、多酚类、黄酮类、生物碱类、皂苷类等多种类型的苦味物质,黄酮类化合物是其中重要的苦味物质类型,在其中分离及鉴定到24种苦味化合物。结合代谢组学和定量分析,明确了山奈酚、异槲皮苷、木犀草素、槲皮素和紫云英苷是香椿中的关键苦味物质。烫漂处理是较优的香椿降苦方法。研究结果可为香椿苦味控制及香椿制品品质提升提供依据。更多还原

【Abstract】 Toona sinensis belongs to Toona of Meliaceae,which has a unique taste and has always enjoyed its laudatory name "vegetable on the tree".Toona sinensis has been planted in 18 provinces all over the country and has developed into a modern characteristic agriculture industry of the "Enriching Project".However,the bitterness of Toona sinensis affects consumers’ satisfaction and acceptability,which restricts the development of Toona sinensis industry.At present,the research on Toona sinensis mainly focuses on volatile compounds and biological activities,and there are few reports on its bitter compounds.Based on the above,this paper intends to analyze the bitterness and all kinds of potential bitter compounds of Toona sinensis,clarify the main types of bitter compounds,analyze the key bitter compounds,and explore the way of reducing bitterness.The main results are as follows:(1)The results of sensory evaluation of Toona sinensis from different producing areas and different picking periods showed that the bitterness intensity of Toona sinensis samples from different origin was different,and the overall trend was increasing from north to south,and the bitterness value of Yunnan Toon was the highest(4.80).The bitterness values of Ankang green Toon and Ankang red Toon generally showed an upward trend with the delay of picking.The correlation analysis between the bitter value of Toona sinensis and the contents of various potential bitter compounds showed that the contents of total phenols and total flavonoids in Toona sinensis from different origin and different picking periods were significantly positively correlated with the bitter value,and it was preliminarily judged that phenols and flavonoids were important compound types related to the bitter formation of Toona sinensis.(2)Based on the analysis of non-target metabonomics,2532 different metabolites were screened from Yunnan Toon,Chongqing Toon and Ningxia Toon.On the basis of all kinds of differential metabolites identified,52 kinds of bitter metabolites,including 12 kinds of amino acids,22 kinds of flavonoids,6 kinds of polyphenols,8 kinds of alkaloids and 4 kinds of saponins,were screened out by relying on the public database of bitter compounds and related references.Further,taking bitterness value as the dependent variable,11 key differential metabolites were screened by partial least square regression analysis,among which 7 were flavonoids,namely scutellarein,kaempferol,isoquercitrin,luteolin,morin,quercetin and astragalin.The quantity,relative abundance and differences between groups of bitter compounds were analyzed,and it was found that flavonoids were the main potential bitter compounds of Toona sinensis.(3)According to the guidance of sensory evaluation,the bitter compounds in Yunnan Toon were effectively separated by ethanol extraction,ethyl acetate extraction and column chromatography,and the flavonoids with high purity were obtained.The two components FIV-13 and F-IV-14 with the highest bitterness activity in the ethyl acetate extraction component were analyzed by UPLC-MS/MS,and a total of 24 flavonoids bitter compounds were identified.These bitter compounds include five key flavonoid metabolites(kaempferol,isoquercitrin,luteolin,quercetin and astragalin)which have been screened by non-target metabolomics analysis and contributed greatly to the bitter difference of Toona sinensis.(4)The bitterness of Toona sinensis was reduced by blanching,ultrasonication,salt immersion and blanching after salt immersion.The results showed that both blanching after salt immersion and blanching could significantly reduce the bitterness of Toona sinensis.Quantitative analysis of 9 kinds of flavonoids bitter compounds in Toona sinensis without and with different bitter reducing treatments showed that isoquercitrin,astragaloside,quercetin,kaempferol and luteolin were all high in content and were positively correlated with the bitter value,which verified that these five kinds of flavonoids were the key bitter compounds in Toona sinensis.Comprehensively comparing the changes in color,bitterness value,bitter compounds and volatile components,blanching treatment has a better bitterness reduction effect.To sum up,Toona sinensis contains many kinds of bitter compounds,such as amino acids,polyphenols,flavonoids,alkaloids,saponins,etc.Flavonoids are an important type of bitter compounds,and 24 kinds of bitter compounds were isolated and identified.Combined with metabonomics and quantitative analysis,it is clear that kaempferol,isoquercitrin,luteolin,quercetin and astragaloside are the key bitter compounds in Toona sinensis.Blanching treatment is a better method to reduce the bitterness of Toona sinensis.The research results provide a basis for controlling the bitterness of Toona sinensis and improving the quality of Toona sinensis products.更多还原