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Fermentation of tea in aqueous suspension
Author(s) -
Millin David J.,
Swaine Derwent
Publication year - 1981
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.2740320909
Subject(s) - chemistry , fermentation , total dissolved solids , aqueous solution , oxygen , substrate (aquarium) , limiting , aqueous suspension , suspension (topology) , pigment , diffusion , chromatography , food science , organic chemistry , mechanical engineering , oceanography , physics , mathematics , environmental engineering , homotopy , pure mathematics , engineering , thermodynamics , geology
The fermentation of macerated tea leaf in aqueous suspension has been studied both manometrically and in a suitably controlled fermentation vessel. Oxygen consumption proceeded rapidly at a steady rate for an initial period, termed the primary fermentation, then decreased sharply as the availability of simple polyphenol substrates became rate limiting. Maximum reaction rates were observed at 20‐35 mg ml −1 total solids, as a result of substrate inhibition. At higher concentrations of solids reaction rates were also affected by diffusion effects within the leaf particles. At 50 mg ml −1 total solids and 25°C the system approximated to Michaelis‐Menton kinetics with K m 02 = 5 × 10 −5 M and V max corresponding to a primary fermentation time (PFT) of 10‐15 min. The PFT corresponded with the attainment of maximum total colour and maximum level of theaflavins (TF) (often >30% of total colour). Beyond the PFT total colour remained constant, TFs decreased and non‐dialysable pigments increased with time. At fixed levels of dissolved oxygen and solids concentration > 60 mg ml −1 the proportion of TFs was inversely related to solids concentration. At 50 mg ml −1 total solids TFs increased to ca 60% of total colour as the dissolved oxygen level was increased to 0.175 mM. As temperature was increased from 15‐35°C the reaction rate increased, the proportion of TFs decreased slightly and thearubigins of intermediate molecular weight increased markedly.