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Mechanical creep of tea leaves
Author(s) -
Lee YaoTsung,
Jhao YiSheng,
Chiang Donyao,
Lee Sanboh
Publication year - 2021
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.10721
Subject(s) - creep , arrhenius equation , materials science , steaming , deformation (meteorology) , stress (linguistics) , composite material , thermodynamics , physics , kinetics , classical mechanics , linguistics , philosophy
BACKGROUND Tea processing involves fermentation, withering, steaming or pan‐firing, rolling, baking, and drying. Some of these steps are performed at a high temperatures. At such temperatures the creep of the tea leaves plays an important role in the quality of tea. In materials science, creep is the tendency of a tea leaf to move slowly or defom permanently under a constant load. There has been much research on the mechanical properties of the outmost cuticular layer of leaves but there are few reports addressing the mechanical properties of whole leaves. RESULTS We cut tea leaf into specimen of dog‐bone shape and measure the time‐dependent creep deformation using a dynamic mechnical analyzer. Three different tea leaves grown in Taiwan were examined. The nonlinear Burgers model is proposed to describe the creep deformation of the tea leaves. CONCLUSIONS The creep of the tea leaves consists of primary and steady states, and the creep deformation is accurately described by the Kelvin representation of the nonlinear Burgers model. The viscosities in the primary stages satisfied the Arrhenius equation, and the activation energies were determined. The stress exponents for the creep of the tea leaves were less than unity. The Maxwell representation of the Burgers model is mathematically equivalent to the Kelvin representation of the Burgers model and can also be used to explain the creep of tea leaves. © 2020 Society of Chemical Industry