Guo Cheng, Shen Wangyang, Jin Weiping, Jia Xiwu, Ji Zhili, Li Jinling, Li Bin
College of Food Science and Engineering, Wuhan Polytechnic University, Wuhan, China.
Key Laboratory for Deep Processing of Major Grain and Oil (Wuhan Polytechnic University), Ministry of Education, Wuhan, China.
J Food Sci. 2023 Oct;88(10):4068-4078. doi: 10.1111/1750-3841.16750. Epub 2023 Aug 25.
Colloidal nanoparticles in tea infusion are the link connecting micromolecular mechanism and macro-aggregation process of tea cream formation. In order to elucidate, the kinetics mechanism of green tea nanoparticles (gTNPs) aggregation, zeta-potentials, total average aggregation (TAA) rates, and critical coagulation concentration (CCC) in the presence of various pH and metal ions were investigated. Additionally, the effect of temperature on gTNPs aggregation was further explored. The results revealed that the TAA rate of gTNPs increased with decreasing pH values, the CCC of gTNPs increased in the order Mg ≈ Ca < Na ≈ K . The reason was that different positive ions changed the surface electric field strength of gTNPs to a different extent. Furthermore, it was indicated that low temperature could promote gTNPs aggregation in indirect way. Low temperature promoted the binding of epigallocatechin gallate (EGCG) and caffeine, and the combination between gTNPs and EGCG-caffeine complexes weakened the stability of gTNPs resulting from reduction in electrostatic repulsion. PRACTICAL APPLICATION: Tea is a popular beverage all over the world. This research revealed the mechanism of green tea nanoparticles aggregation and laid a theoretical foundation for the regulation of tea cream formation in tea beverage.
茶浸液中的胶体纳米颗粒是连接茶乳酪形成的微观分子机制和宏观聚集过程的纽带。为了阐明绿茶纳米颗粒（gTNPs）聚集的动力学机制，研究了在不同pH值和金属离子存在下的ζ电位、总平均聚集（TAA）速率和临界聚沉浓度（CCC）。此外，还进一步探讨了温度对gTNPs聚集的影响。结果表明，gTNPs的TAA速率随pH值降低而增加，gTNPs的CCC按Mg≈Ca＜Na≈K的顺序增加。原因是不同的阳离子对gTNPs表面电场强度的改变程度不同。此外，结果表明低温可以间接促进gTNPs聚集。低温促进表没食子儿茶素没食子酸酯（EGCG）与咖啡因的结合，gTNPs与EGCG - 咖啡因复合物之间的结合削弱了由于静电排斥减少而导致的gTNPs稳定性。实际应用：茶是全球流行的饮品。本研究揭示了绿茶纳米颗粒聚集的机制，为调控茶饮料中茶乳酪的形成奠定了理论基础。
