Department of Chemistry and Pharmacy, Food Chemistry, Emil Fischer Center, Friedrich-Alexander University Erlangen-Nuremberg.
Food Funct. 2011 May;2(5):265-72. doi: 10.1039/c0fo00180e. Epub 2011 Apr 15.
Coffee shows distinct antimicrobial activity against several bacterial genera. The present study investigated molecular mechanisms and active ingredients mediating the antimicrobial effect of coffee. Depending on concentration, roasted, but not raw coffee brew inhibited the growth of Escherichia coli and Listeria innocua. Several coffee ingredients with known antibacterial properties were tested for their contribution to the observed effect. In natural concentration, caffeine, ferulic acid and a mixture of all test compounds showed very weak, but significant activity, whereas trigonelline, 5-(hydroxymethyl)furfural, chlorogenic acid, nicotinic acid, caffeic acid, and methylglyoxal were not active. Antimicrobial activity, however, was completely abolished by addition of catalase indicating that H(2)O(2) is a major antimicrobial coffee component. In accordance with this assumption, bacterial counts during 16 h of incubation were inversely related to the H(2)O(2) concentration in the incubation solution. Pure H(2)O(2) showed slightly weaker activity. The H(2)O(2) dependent antimicrobial activity of coffee could be mimicked by a reaction mixture of d-ribose and l-lysine (30 min 120 °C) indicating that H(2)O(2) is generated in the coffee brew by Maillard reaction products. Identification of H(2)O(2) as major antimicrobial coffee component is important to evaluate the application of coffee or coffee extracts as natural preservatives.
咖啡对几种细菌属具有明显的抗菌活性。本研究调查了介导咖啡抗菌作用的分子机制和活性成分。根据浓度的不同，烘焙但未烘焙的咖啡酿造物抑制了大肠杆菌和无害李斯特菌的生长。测试了几种具有已知抗菌特性的咖啡成分，以确定它们对观察到的效果的贡献。在自然浓度下，咖啡因、阿魏酸和所有测试化合物的混合物表现出非常弱但显著的活性，而瓜氨酸、5-(羟甲基)糠醛、绿原酸、烟酸、咖啡酸和甲基乙二醛则没有活性。然而，添加过氧化氢酶完全消除了抗菌活性，表明 H(2)O(2)是咖啡的主要抗菌成分。根据这一假设，在 16 小时的孵育过程中，细菌计数与孵育溶液中的 H(2)O(2)浓度呈反比。纯 H(2)O(2)的活性略弱。通过 d-核糖和 l-赖氨酸（30 分钟 120°C）的反应混合物可以模拟咖啡的 H(2)O(2)依赖性抗菌活性，这表明 H(2)O(2)是由美拉德反应产物在咖啡酿造物中生成的。将 H(2)O(2)鉴定为咖啡的主要抗菌成分对于评估咖啡或咖啡提取物作为天然防腐剂的应用非常重要。
