Department of Biochemistry and Molecular Biology, Mississippi State University, Mississippi State, MS 39762, USA.
Int J Food Microbiol. 2010 Feb 28;137(2-3):154-60. doi: 10.1016/j.ijfoodmicro.2009.12.011. Epub 2009 Dec 13.
Starch-based films impregnated with fresh tannic acid (FTA/starch film) and thermally processed tannic acid (PTA/starch film) were assessed for inhibition of Escherichia coli O157:H7 and Listeria monocytogenes. Disc-diffusion assay revealed that the PTA/starch film showed larger clear zone around the film on the bacterial lawn than the FTA/starch film at the same tannic acid concentrations (0.45 to 4.5mg per disc). Viable cell count assays in tryptic soy broth showed that the PTA/starch film also had a stronger antimicrobial activity on these foodborne pathogens than the FTA/starch film. L. monocytogenes did not replicate in trypic soy broth containing the FTA/starch film for the first 8h but multiplied up to 9.22 log CFU/ml at 48 h of incubation. The PTA/starch film caused a 2.72-log decrease in L. monocytogenes cells over the same time period. While 5-log E. coli O157:H7 cells were inactivated by the FTA/starch film within 48 h, more than 7-log E. coli O157:H7 cells were killed by the PTA/starch film over the same period. The antimicrobial activity of FTA/starch and PTA/starch film was primarily pH independent. HPLC measurement of the FTA or PTA release from starch film in water revealed that their release kinetic curves were in well match with their inactivation curves for E. coli O157:H7 and L. monocytogenes in 0.1% peptone water. In addition to antimicrobial activity, FTA showed antioxidant activity on soybean oil by doubling the induction time of oil oxidation. PTA further enhanced the oxidative stability of the oil by 17%. These results suggested that the use of processed tannic acid in starch films could improve the safety and quality of foods.
基于淀粉的薄膜用新鲜鞣酸（FTA/淀粉膜）和热处理鞣酸（PTA/淀粉膜）浸渍，以评估其对大肠杆菌 O157:H7 和单核细胞增生李斯特菌的抑制作用。圆盘扩散试验显示，在相同鞣酸浓度（每个圆盘 0.45 至 4.5mg）下，PTA/淀粉膜在细菌菌苔周围的膜显示出更大的透明区。在胰蛋白胨大豆肉汤中的活菌计数试验表明，PTA/淀粉膜对这些食源性病原体的抗菌活性也强于 FTA/淀粉膜。李斯特菌在含 FTA/淀粉膜的胰蛋白胨大豆肉汤中在最初的 8 小时内没有复制，但在孵育 48 小时时繁殖到 9.22 对数 CFU/ml。在相同时间内，PTA/淀粉膜使李斯特菌细胞减少了 2.72 对数。虽然 FTA/淀粉膜在 48 小时内使 5 对数的大肠杆菌 O157:H7 细胞失活，但在相同时间内，PTA/淀粉膜杀死了超过 7 对数的大肠杆菌 O157:H7 细胞。FTA/淀粉和 PTA/淀粉膜的抗菌活性主要与 pH 无关。在水中从淀粉膜中释放的 FTA 或 PTA 的 HPLC 测量表明，它们的释放动力学曲线与它们在 0.1%蛋白胨水中对大肠杆菌 O157:H7 和单核细胞增生李斯特菌的失活动力学曲线非常吻合。除了抗菌活性外，FTA 还通过将油氧化的诱导时间加倍来表现出对大豆油的抗氧化活性。PTA 通过提高 17%进一步增强了油的氧化稳定性。这些结果表明，在淀粉膜中使用处理过的鞣酸可以提高食品的安全性和质量。
