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Kinetics of Thermal Degradation of Chlorophyll in Spinach Puree a
Author(s) -
GUPTE S. M.,
ELBISI H. M.,
FRANCIS F. J.
Publication year - 1964
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1964.tb01747.x
Subject(s) - enthalpy , activation energy , reaction rate constant , chemistry , analytical chemistry (journal) , spinach , d value , atmospheric temperature range , kinetics , mole , degradation (telecommunications) , pigment , chromatography , thermodynamics , biochemistry , organic chemistry , food science , physics , telecommunications , quantum mechanics , computer science
SUMMARY The kinetics of chlorophyll degradation in spinach purée were studied over the temperature range 260—300°F, using thermal‐death‐time tubes heated in a constant‐temperature oil bath. Pigments were separated by column chromatography, and their concentrations determined spectrophotometrically. A semilogarithmic (first‐order) plot of the residual pigment vs. time was used to illustrate the thermal degradation rate (TDR). Although the major portions of the TDR curves were apparently linear, several abnormalities were observed during the initial test intervals. Regression coefficients were computed for the linear portions and used to compute the various thermo‐dynamic functions characteristic of the degradation reactions. The following values respectively represent the average determinations for chlorophylls a and b. The TDR constant k , (2.3/D, D , D being decimal reduction time in sec), 1.1 × 10 −2 and 0.52 × 10 −2 sec −1 ; the temperature coefficient Q 10 (log −1 18/ z , z being °F affecting 10‐fold change in k , or D ), 1.58 and 1.26; the activation energy E , 143 and 35 Kcal mole −1 ; the enthalpy H , 142 and 34 Kcal mole −1 ; the free energy & Delta; F , 29 and 32 Kcal mole −1 ; and the entropy & Delta; S , 268 and 5 cal deg −1 mole −1.