Zaheer Samina, Kew Ben, Louca Chris, Hafizi Sassan, Sarkar Anwesha, Mutahar Mahdi
School of Dental, Health and Care Professions, University of Portsmouth, Portsmouth, United Kingdom.
Food Colloids and Bioprocessing Group, School of Food Science and Nutrition, University of Leeds, Leeds, United Kingdom.
PLoS One. 2025 Sep 3;20(9):e0330023. doi: 10.1371/journal.pone.0330023. eCollection 2025.
This study investigates the impact of a sweetened acidic beverage, an apple juice (J) consumption on the tribological properties, viscoelasticity, and protein concentration/ composition of human saliva. Using a combination of tribological measurements, quartz crystal microbalance with dissipation monitoring (QCM-D), and protein analysis, we assessed how J may affect saliva's lubricating behaviour and adsorbed salivary film characteristics compared to water (control). Tribological results revealed that saliva (collected from 32 healthy adults) exposed to water or J exhibited increased friction when compared to unstimulated whole mouth saliva (uWMS), particularly within the boundary lubrication regime. A one-min rinse with water or J caused salivary delubrication, with water having a greater delubricating effect (p < 0.05) than that of J. Strikingly, the friction coefficients reverted to those for uWMS after 10 min (p > 0.05) highlighting the transient nature of delubrication caused by J consumption. This transient phenomenon was also evident in QCM-D measurements, where J transformed the ex vivo salivary film into a rigid layer, which reverted upon buffer application on model hydrophilic surfaces. Analysis of total protein concentration (TPC) showed that water significantly reduced TPC after one min, while J required 10 min to achieve similar TPC reduction. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) revealed that salivary cystatins and carbonic anhydrase significantly changed after J intervention, unlike water. This study highlights limited effects of J on salivary delubrication and adsorption. Building upon our findings, future research should investigate how repeated exposure to sweetened acidic beverages influences in vivo salivary pellicle dynamics and impacts to oral health.
本研究调查了一种甜味酸性饮料（苹果汁，J）的摄入对人类唾液的摩擦学特性、粘弹性以及蛋白质浓度/组成的影响。通过结合摩擦学测量、带耗散监测的石英晶体微天平（QCM-D）和蛋白质分析，我们评估了与水（对照）相比，J如何影响唾液的润滑行为和吸附唾液膜的特性。摩擦学结果显示，与未刺激的全口唾液（uWMS）相比，接触水或J的唾液（从32名健康成年人采集）表现出摩擦力增加，特别是在边界润滑状态下。用水或J冲洗一分钟会导致唾液脱润滑，水的脱润滑效果（p < 0.05）比J更大。令人惊讶的是，10分钟后摩擦系数恢复到uWMS的水平（p > 0.05），突出了饮用J导致的脱润滑的短暂性。这种短暂现象在QCM-D测量中也很明显，其中J将离体唾液膜转变为刚性层，在模型亲水表面施加缓冲液后又恢复原状。总蛋白浓度（TPC）分析表明，水在一分钟后显著降低了TPC，而J需要10分钟才能实现类似的TPC降低。十二烷基硫酸钠聚丙烯酰胺凝胶电泳（SDS-PAGE）显示，与水不同，J干预后唾液中的半胱氨酸蛋白酶抑制剂和碳酸酐酶显著变化。本研究强调了J对唾液脱润滑和吸附的有限影响。基于我们的研究结果，未来的研究应调查反复接触甜味酸性饮料如何影响体内唾液薄膜动力学以及对口腔健康的影响。
