Research On The Physical Properties And Moisture Sorption Isotherms Of Tea Leaves

Tea is the characteristic agriculture and important economic crops, which inner itance of the tea cultural. Tea production in our country has important economic v alue and social significance. Research in physical characteristics of tea has very i mportant meaning in tea engineering and development technology. Moisture absorpt ion/desorption balance isotherms of tea is very important to the reasonable control of the tea storage conditions. Therefore this paper research in the physical proper ties of tea and moisture absorption desorption characteristics, eventually got the ch ange rule.The physical variable parameters of spring green tea in tea processing were i nvestigated. The results show that the moisture content of tea dropped in processin g, the moisture content declined fastest in the tea form processing, while in the te a rolling processing the moisture content of tea reduced little; the bulk density of the processed tea is largest while the bulk density is smallest for fresh tea leaves; the porosity of fresh tea leaves is largest while for the rolled tea leaves the poro sity is smallest, and the variation range of porosity is0.696～0.732; the repose an gle during the whole process course vary between50°nd60°; the static friction a ngle is largest against aluminum,which is smaller for the adhesive tape and show little difference against copper plate. The static friction angle is smallest of the f ormed tea against all the tea machinery materials.Study in physical properties of tea in rolling process The results show that:t ea moisture content and rolling time is negatively correlated; tea elasticity and roll ing time is linear correlated, tea flexibility and plasticity are first increase then red uce in the rolling time, the best rolling time for tea forming is25min or so; the t rend of tea porosity with rolling time is a parabolic trend.The equilibrium moisture contents of green tea were determined by the gravi metric static method. Tea of moisture absorption balance abtiained after seven days and desorption balance abtianed after five days, in0.967water activity, all the te a got mouldy after the3or4days; Tea with water balance moisture content incr eased activity The equilibrium moisture content was affected by temperature and w ater activity. While there was no big difference between varies tea. An hysteresis effect was observed. The experimental data of sorption were fitted by three model s (Modified Halsey model, Modified Oswin model and the GAB model). The GA B model was found to be the most suitable for describing the sorption isotherms of green tea leaves.