Surface conditioning of stainless steel coupons with skim milk solutions at different pH values and its effect on bacterial adherence
Surface conditioning of stainless steel coupons with skim milk solutions at different pH values and its effect on bacterial adherence
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不同pH值脱脂奶溶液对不锈钢试样的表面调节及其对细菌粘附的影响
DOI：
10.1016/j.foodcont.2010.06.012
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
T. Uchino
中科院分区：
文献类型：
--
作者：
N. M. Dat;D. Hamanaka;F. Tanaka;T. Uchino
在乳制品工业中，在洗涤和发酵过程中，与牛奶或不同pH值的牛奶残留物接触的加工表面会改变细菌的附着行为。为了模拟和阐明这一过程，用不同pH值的脱脂牛奶对不锈钢板进行了处理，并研究了表面处理对细菌粘附的影响。当牛奶pH值降低时（通过添加盐酸），牛奶蛋白凝固，并在不锈钢板上形成沉淀。当牛奶pH值增加时（通过添加氢氧化钠），在调理后的表面上观察到很少可见的沉积物。然后将获得的表面暴露于副干酪乳杆菌亚种的悬浮液中，以验证细菌的粘附性。paracasei NBRC 15889。在荧光显微镜下对这些表面上的贴壁细胞进行计数。在与细菌细胞短暂接触（30分钟）后，与对照组（未经处理的表面）和碱性牛奶样品相比，先前用酸性牛奶处理过的表面（特别是pH从3.8到5.5）的粘附性较低。在pH值范围内，7.03条件下的粘附性最高。结果还表明，随着暴露时间的增加，依恋程度增加。暴露30分钟后，牛奶沉淀物中几乎没有细菌细胞出现。相反，在12小时后，观察到许多细胞存在于这些沉淀物中。为了减少细菌的粘附，当细菌接触时间短暂时，建议使用低pH值的牛奶进行表面调理。长时间的细菌暴露是不可取的任何条件下。
In the dairy industry, processing surfaces contacting milk or milk residues at different pH values during washing and fermentation could change bacterial attachment behavior. In order to simulate and elucidate this process, stainless steel coupons were conditioned with skim milk at different pH values, and the influence of surface conditioning on bacterial adherence was investigated. When milk pH was decreased (by the addition of hydrochloric acid), milk proteins coagulated, and precipitates were made on stainless steel coupons. When milk pH was increased (by the addition of sodium hydroxide), little visible deposit was observed on the surfaces after conditioning. Obtained surfaces were then used to verify bacterial adherence by being exposed to a suspension of Lactobacillus paracasei subsp. paracasei NBRC 15889. The enumeration of adherent cells on these surfaces was carried out under a fluorescence microscope. After short contact with bacterial cells (30 min), surfaces which were previously conditioned with acidic milk, especially in pH from 3.8 to 5.5, had lower adherence in comparison with the control (untreated surface) and with basic milk samples. Conditioning at pH of 7.03 had the highest adherence in the tested pH range. Results also indicated that attachment increased with the exposure time. Very few bacterial cells appeared inside milk precipitates after 30 min of exposure. In contrast, many cells were observed to be present inside these precipitates after 12 h. To decrease bacterial adherence, surface conditioning with milk at low pH is recommended when bacterial contact is brief. Long periods of bacterial exposure are not advisable for any conditioning case.