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The evaluation quality of black tea – based on the characteristics of hygroscopic properties designated by the static method




Key words: 

sorption isotherm of water vapor, BET isotherm, storage stability of teas. 


The aim of the study was to evaluate the hygroscopic properties of black teas, differing in country of origin, based on isotherms of water vapor sorption and characteristics selected parameters of the surface microstructure determining storage and microbiological stability of teas. In order to describe empirically determined sorption isotherms, the equation of Brunauer, Emmett and Teller (BET) was transformed in the range of water activity 0.07≤aw≤0.33. The equation was characterized based on the correlation coefficient (R2) and the fit standard error (FitStdErr). In order to characterize the microstructure of the surface were determined: monomolecular layer capacity, proper surface of sorption, total capacity of the capillaries and radius of capillaries subject to filing after initiating the capillary condensation. Based on extensive investigations, it was found that sorption isotherms determined empirically in tested teas, were characterized by sigmoidal in shape and, according to the classification of Brunauer, showed similarity to the isotherms of type II. Based on the evaluation parameters of the microstructure found the higher storage stability characterized the tea from Indonesia, and i Sri Lanka which may be due to differences in the microstructure of the surface resulting from the tea origin and parameters of the drying process.

dr inż. Millena RUSZKOWSKA dr inż. Przemysław DMOWSKI 

Gdynia Maritime University Faculty of Entrepreneurship and Quality Science 

Department of Commodity and Quality Science 

ul. Morska 81-85, 81-225 Gdynia, Poland 

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