Department of Food Science and Human Nutrition, The University of Maine, 5735 Hitchner Hall, Orono, ME 04469, United States.
Int J Food Microbiol. 2010 Apr 30;139(1-2):102-7. doi: 10.1016/j.ijfoodmicro.2010.01.035. Epub 2010 Feb 1.
We investigated the antimicrobial effect of constituents of the American cranberry (Vaccinium macrocarpon); sugar plus organic acids, phenolics, and anthocyanins, against Escherichia coli O157:H7. Each fractional component was assayed over a 24-h period with 5-log initial inocula to determine the minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), and log CFU/ml reductions, at their native pH and neutral pH. Each fraction produced significant reductions (P<0.05) at the native pH: MICs for sugars plus organic, phenolics, and anthocyanins were 5.6/2.6 Brix/acid (citric acid equivalents) 2.70g/L (gallic acid equivalent), and 14.80mg/L (cyanidin-3-glucoside equivalent), respectively. Sugars plus organic acids at native pH (3) produced a reduction below detectable limits (<1 log CFU/ml) compared to the control at 24h for 11.3/5.2 and 5.6/2.6 Brix/acid. Phenolics at native pH (4) produced reductions below detectable limits compared to the control at 24h and initial inocula for treatments of 5.40 and 2.70g/L. Anthocyanins at native pH (2) produced reductions below detectable limits for treatments of 29.15 and 14.80mg/L cyanidin-3-glucoside equivalents. Neutralized phenolics and anthocyanins had the same MIC and MBC as those at their native pH. Neutralized sugars plus organic acids did not inhibit bacterial growth compared to the control. Neutralized phenolics reduced bacteria below detectable limits in treatments of 5.40g/L and 2.70g/L compared to the control. Neutralized anthocyanins reduced bacterial growth below detectable limits at the concentration of 29.15mg/L, but at 14.80mg/L there was no significant reduction. Stationary-phase cells of E. coli O157:H7 were treated with 5% of each fraction in 0.8% NaCl for 20min and viewed under transmission electron microscopy. All fractions caused significant damage compared the control. Sugars plus organic acids caused visible osmotic stress, while phenolics and anthocyanins caused disintegration of the outer membrane.
我们研究了蔓越莓（Vaccinium macrocarpon）的成分对大肠杆菌 O157:H7 的抗菌作用；糖加上有机酸、酚类和花青素。每个分数成分在初始接种物为 5 个对数的情况下进行 24 小时测试，以确定最小抑菌浓度 (MIC)、最小杀菌浓度 (MBC) 和 log CFU/ml 减少量，在其天然 pH 和中性 pH 下。每个分数在天然 pH 下都产生了显著的减少（P<0.05）：糖加上有机酸、酚类和花青素的 MIC 分别为 5.6/2.6 Brix/酸（柠檬酸当量）2.70g/L（没食子酸当量）和 14.80mg/L（矢车菊素-3-葡萄糖苷当量）。糖加上有机酸在天然 pH（3）下产生的减少量低于对照在 24 小时时的检测限以下（<1 log CFU/ml），对于 11.3/5.2 和 5.6/2.6 Brix/酸。酚类在天然 pH（4）下产生的减少量低于对照在 24 小时和初始接种物时的检测限，对于 5.40 和 2.70g/L 的处理。天然 pH 下的花青素（2）对 29.15 和 14.80mg/L 矢车菊素-3-葡萄糖苷当量的处理产生的减少量低于检测限。中和后的酚类和花青素的 MIC 和 MBC 与天然 pH 时相同。与对照相比，中和后的糖加上有机酸没有抑制细菌生长。中和后的酚类在 5.40g/L 和 2.70g/L 的处理中使细菌减少到检测限以下，而与对照相比，中和后的花青素在浓度为 29.15mg/L 时没有显著减少。大肠杆菌 O157:H7 的静止期细胞用 0.8%NaCl 中的每种分数的 5%处理 20min，然后在透射电子显微镜下观察。与对照相比，所有分数都造成了显著的损伤。糖加上有机酸导致可见的渗透压应激，而酚类和花青素导致外膜的崩解。
