The glucosinolates which are specialized plant metabolites of Brassica vegetables are prone to hydrolysis catalyzed by an endogenous enzyme myrosinase (thioglycoside hydrolase, thioglucosidase) that exists in Brassica plant tissue causing volatile isothiocyanates release. Currently existing literature data on the inactivation of myrosinase is insufficient in particular for use in the analysis of volatile and odor compounds in vegetables rich in glucosinolates. In this study, the impact of different metal salts in effective inactivation of enzyme activity was investigated by solid-phase microextraction (SPME) and GC/MS system in aqueous samples and kohlrabi matrix. A saturated solution of calcium chloride which is commonly used to stop enzyme activity in plant tissue inactivates the myrosinase–glucosinolate system. However, even without the participation of myrosinase, it changes the reaction pathway towards nitrile formation. The model experiment shows that optimum efficiency in inhibition of the enzyme system shows iron(III) ions, silver ions, and anhydride sodium sulfate resulting in no volatile products derived from glucosinolates. However, in the kohlrabi matrix, the strongest enzyme inhibition effect was observed for silver salt resulting in no volatile products, also both anhydrous Na2SO4 and saturated CaCl2 solution seem to be useful inhibitors in flavor studies.

中文翻译：

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金属盐对白芥菜种子硫葡糖苷酶的灭活作用

作为芸苔属蔬菜的特殊植物代谢物的硫代葡萄糖苷易于被芸苔属植物组织中存在的内源性黑芥子酶（硫糖苷水解酶，硫代葡萄糖苷酶）催化水解，导致挥发性异硫氰酸酯释放。目前关于黑芥子酶失活的现有文献数据不足以用于分析富含硫代葡萄糖苷的蔬菜中的挥发性和气味化合物。在本研究中，通过固相微萃取 (SPME) 和 GC/MS 系统在水性样品和大头菜基质中研究了不同金属盐对有效灭活酶活性的影响。通常用于停止植物组织中酶活性的氯化钙饱和溶液会使黑芥子酶-芥子油苷系统失活。然而，即使没有黑芥子酶的参与，它也会改变向腈形成的反应途径。模型实验表明，酶系统抑制的最佳效率显示铁 (III) 离子、银离子和无水硫酸钠导致没有源自硫代葡萄糖苷的挥发性产物。然而，在大头菜基质中，观察到银盐最强的酶抑制作用，导致没有挥发性产物，而且无水 Na2SO4 和饱和 CaCl2 溶液似乎都是风味研究中有用的抑制剂。