Ma Shuang, Shi Ce, Wang Cuina, Guo Mingruo
1 Department of Food Science, College of Food Science and Engineering, Jilin University, Changchun, 130062, Peoples Republic of China.
2 Department of Nutrition and Food Sciences, College of Agriculture and Life Sciences, The University of Vermont, Burlington, Vermont 05405, USA.
J Food Prot. 2017 Oct;80(10):1657-1665. doi: 10.4315/0362-028X.JFP-17-078.
Totarol is a natural antimicrobial compound extracted from the heartwood of Podocarpus totara, a conifer native to New Zealand. The effects of whey protein-totarol nanoparticles treated with ultrasound on the physiochemical properties and the growth of Staphylococcus aureus were investigated. The particle size of whey protein-totarol nanoparticles was reduced by ultrasound treatment from 31.24 ± 5.31 to 24.20 ± 4.02 nm, and the size distribution was also narrowed by the treatment. Viscosity and modulus data indicated that the flow behaviors of whey protein-totarol nanoparticles seemed to be Newtonian and exerted a typical viscoelastic fluid at protein content of 15% (w/v). Rheological properties were more insensitive to ultrasonic time. Time-killing assays, agar diffusion tests, the cell membrane damage analysis, and microstructure were exploited to study the antibacterial properties of whey protein-totarol nanoparticles. The MIC of whey protein-totarol nanoparticles after ultrasound treatment decreased from 4 to 2 μg/mL compared with that without ultrasound treatment. Whey protein-totarol nanoparticles treated with ultrasound resulted in a significant (P < 0.05) decrease in time killing after 24 h. The agar diffusion results showed that the inhibition zones of whey protein-totarol nanoparticles were 12 and 36 mm for untreated and treated with ultrasound, respectively. The cell membrane damages and the microstructure changes also proved that whey protein-totarol nanoparticles treated with ultrasound had strong antibacterial activities against S. aureus and that the antibacterial effectiveness enhanced with the increasing of ultrasonic time. These findings suggested that whey protein-totarol nanoparticles treated with ultrasound were more effective against S. aureus than untreated nanoparticles.
托塔酚是一种从新西兰本土针叶树罗汉松心材中提取的天然抗菌化合物。研究了经超声处理的乳清蛋白 - 托塔酚纳米颗粒对金黄色葡萄球菌理化性质及生长的影响。超声处理使乳清蛋白 - 托塔酚纳米颗粒的粒径从31.24±5.31纳米减小至24.20±4.02纳米，且粒径分布也因该处理而变窄。粘度和模量数据表明，在蛋白质含量为15%（w/v）时，乳清蛋白 - 托塔酚纳米颗粒的流动行为似乎呈牛顿流体特性，并表现出典型的粘弹性流体性质。流变学性质对超声时间更不敏感。采用时间 - 杀菌试验、琼脂扩散试验、细胞膜损伤分析和微观结构研究了乳清蛋白 - 托塔酚纳米颗粒的抗菌性能。与未超声处理的相比，超声处理后的乳清蛋白 - 托塔酚纳米颗粒的最低抑菌浓度从4μg/mL降至2μg/mL。超声处理的乳清蛋白 - 托塔酚纳米颗粒在24小时后导致时间 - 杀菌率显著（P<0.05）下降。琼脂扩散结果表明，未处理和超声处理的乳清蛋白 - 托塔酚纳米颗粒的抑菌圈分别为12毫米和36毫米。细胞膜损伤和微观结构变化也证明，超声处理的乳清蛋白 - 托塔酚纳米颗粒对金黄色葡萄球菌具有较强的抗菌活性，且抗菌效果随超声时间的增加而增强。这些发现表明，超声处理的乳清蛋白 - 托塔酚纳米颗粒对金黄色葡萄球菌的抗菌效果比未处理的纳米颗粒更好。
