Exploratory Study On The Relationship Between Micro-nanoparticles And Taste Of Black Tea

The black tea born along with the process that taste components got out the leaves and dissolved into water.Multi-phase system of black tea is composed by true solution phase,colloid phase,and suspension phase.At present,research of tea taste is usually focused on the relationship between taste components concentration and tea taste,however research of the relationship between the micro-nanoparticles existing in the tea and tea taste is rare.In this paper,the relationship between micro-nanoparticles and taste of Wuyi black tea was studied by collochemical and biochemical methods.In this study we found that there were abundant of micro-nanoparticles in tea extraction,and the size of those particles distributed from tens to thousands nanometers.The size of particles changed regularly along the process of temperature rise and reduction,being 180 nm at high temperature and distributing widely with the reduction of temperature.Particles whose size was smaller than 100 nm appeared above 70 ℃,and particles whose size was larger than 5000 nm appeared below 35℃.The tea extraction was subjected to microfiltration with cellulose acetate filter(0.22 μm)at 70℃,60℃,50℃,40℃ and 30℃ to separate the particles.Then the sensory evaluation was done,and the taste components were analyzed.Results showed that bitterness,astringent feeling,aftersweet and Shengjin sense changed significantly after the microfiltration,and the changes of the taste didn’t match the changes of taste components concentration.To study more about the colloid phase,sensory evaluation and chemical analysis of resuspended particles were done.The results showed that though the taste components concentration was lower than their threshold value concentration,the resuspended particles showed strongly bitterness and astringency.Comparing the resuspended particles with size between 100-200 nm and size larger than 200 nm,only particles with size larger than 200 nm exhibited bitterness and astringency which showed that the taste of tea particles was related to its size.Finally,comparing the tea made with hot water and cold water,it was found that most of the taste components aggregated together in the tea,and the molecular weight of aggregation was greater than 50 kDa.The hot-water-made tea showed significantly higher light scattering intensity than cold-water-made tea,which meant that hot environment was necessary to induce the formation of larger particles.The particles which were larger than 5000 nm only existed in the hot-water-made tea.With studying of the colloidal particles properties,taste components concentration and sensory evaluation,the relationship between particles and bitterness,and the relationship between particles and astringency in Zhengshan black tea were explored,which expanded a new research field of tea taste,and provided a new idea to improve the homogenization of tea beverage,and to develop natural&healthy black tea beverage.