Institute of Food Chemistry, Hamburg School of Food Science, University of Hamburg, Grindelallee 117, Hamburg 20146, Germany.
Institute of Food Chemistry, Hamburg School of Food Science, University of Hamburg, Grindelallee 117, Hamburg 20146, Germany.
Food Res Int. 2018 Jun;108:621-627. doi: 10.1016/j.foodres.2018.04.001. Epub 2018 Apr 4.
Isothiocyanates (ITC) play an important role in health promotion and cancer prevention due to their anti-bacterial, anti-inflammatory, and anti-cancerogenic properties. However, ITC are highly reactive so that a reaction with further food components is very likely. For example, a reaction of ITC with nucleophilic amino acid side chains of proteins such as cysteine and lysine can occur, reducing the bioavailability of indispensable amino acids and protein functions may be altered. Therefore, it is of great interest to investigate the fate of ITC in the food matrix. Accordingly, the aim of the present study was to investigate the interaction of milk proteins and the ITC benzyl isothiocyanate (BITC) and allyl isothiocyanate (AITC) forming dithiocarbamates and thioureas in milk and curd. After incubating milk and curd with pure ITC or ITC-containing garden cress (Lepidium sativum L.), proteins were isolated, digested, and analyzed via LC-ESI-MS/MS as amino acid derivatives ("conjugates"). Protein conjugates of AITC and BITC were detected in all samples investigated. Further, the acidic pH value in curd favored the formation of dithiocarbamates over the formation of thioureas. Slightly acidic or neutral conditions like in fresh milk favored the formation of thioureas. The investigations also indicated that AITC shows a higher reactivity and dithiocarbamates are formed preferably, whereas incubation with BITC lead to less protein conjugates and the ratio of thioureas and dithiocarbamates was more balanced. In addition, amino acid modifications were often analyzed with indirect methods like measuring the decline of the amino acid residues. In this study, the modified amino acids were analyzed directly leading to more reliable results concerning the amount of modification.
异硫氰酸酯 (ITC) 因其具有抗菌、抗炎和抗癌特性，在促进健康和预防癌症方面发挥着重要作用。然而，ITC 具有很高的反应性，因此很可能与其他食物成分发生反应。例如，ITC 可以与半胱氨酸和赖氨酸等蛋白质中的亲核氨基酸侧链发生反应，从而降低必需氨基酸的生物利用度，并且蛋白质的功能可能会发生改变。因此，研究 ITC 在食物基质中的命运具有重要意义。因此，本研究的目的是研究牛奶蛋白与 ITC 苄基异硫氰酸酯 (BITC) 和烯丙基异硫氰酸酯 (AITC) 之间的相互作用，形成牛奶和凝乳中的二硫代氨基甲酸酯和硫脲。在纯 ITC 或含 ITC 的花园水芹（Lepidium sativum L.）孵育牛奶和凝乳后，分离蛋白质，通过 LC-ESI-MS/MS 作为氨基酸衍生物（“缀合物”）进行消化和分析。在所研究的所有样品中都检测到 AITC 和 BITC 的蛋白质缀合物。此外，凝乳中的酸性 pH 值有利于形成二硫代氨基甲酸酯而不是形成硫脲。像新鲜牛奶中的略酸性或中性条件有利于形成硫脲。研究还表明，AITC 表现出更高的反应性，并且优先形成二硫代氨基甲酸酯，而与 BITC 孵育则导致较少的蛋白质缀合物，并且硫脲和二硫代氨基甲酸酯的比例更为平衡。此外，氨基酸修饰通常通过间接方法（如测量氨基酸残基的减少）进行分析。在这项研究中，直接分析修饰的氨基酸，从而获得关于修饰量的更可靠结果。
