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The interfacial factor in the heat‐induced conversion of chlorophyll to pheophytin in green leaves
Author(s) -
Haisman Derek R.,
Clarke Michael W.
Publication year - 1975
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.2740260809
Subject(s) - pheophytin , electrolyte , chlorophyll , chemistry , chlorophyll a , energy conversion efficiency , mesophase , botany , inorganic chemistry , photosynthesis , materials science , organic chemistry , biochemistry , phase (matter) , biology , electrode , optoelectronics , photosystem ii
The rates of the conversion of chlorophyll to pheophytin in the green leaves of common vegetables and other plants at different temperatures in buffered electrolyte systems were studied. Kinetic measurements showed that the conversion only occurred above a threshold temperature of 50–60 °C and was most probably a pseudo‐first order reaction. Rates were found to be proportional to √[H + ]. The dependence of the rate of conversion upon species, temperature and electrolyte type can be explained on the basis of a heat‐induced metamorphosis of the chloroplasts to a smectic mesophase which occludes the chlorophyll. The rate of the reaction then depends on the transfer of hydronium ions across the interface and can be largely controlled by modifying the interfacial potential.