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Coriander leaves are widely used in cooking throughout the world. Thermal degradation kinetics of chlorophyll a, b, and total chlorophyll in coriander leaf puree was investigated at varying levels of pH (4.5-8.5) and processing temperature (80-145°C). Coriander puree at pH 4.5 was processed at 80° to 100°C, whereas that at pH 5.5 to 8.5 was processed at 105° to 145°C. Chlorophyll degradation followed first-order reaction kinetics. Good agreement was found between estimated and experimental chlorophyll retention in all cases (R²>0.80). Activation energies ranged from 6.57 to 96.00 kJ/mol. Reaction rate and activation energy data indicated that chlorophylls were more stable at alkaline pH. Transition state theory was applied to estimate the enthalpy, entropy, and Gibbs free energy of activation. Enthalpy of activation (ΔH#) ranged from 3.46 to 91.99 kJ/mol, whereas entropy of activation (&Delata;S#) ranged from .0.265 to .0.047 kJ/(mol K). The overall free energy change was 107.55 kJ/mol. Results indicated that, the compensation effect did not exist for chlorophyll degradation in coriander puree during thermal processing. [ABSTRACT FROM AUTHOR]

Rheological behavior of coriander and mint leaf puree was determined at temperatures of 30 to 80C. Applicability of various rheological models available in the literature was evaluated. The Herschel–Bulkley model provided a good description of the flow behavior of coriander and mint leaf puree over the temperature range of 30–80C. The Arrhenius model successfully described the effect of temperature on consistency index of coriander and mint puree. The temperature dependence of apparent viscosity of mint puree however did not obey the Arrhenius model. The activation energy of flow for coriander and mint puree was 23.99 and 32.62 kJ/mol, respectively. PRACTICAL APPLICATIONS Flow properties of foods are determined for a number of purposes, such as quality control, understanding the structure, process engineering applications and correlation with sensory evaluation ( Cepeda et al. 2002 ; Nindo et al. 2005 ). Knowledge of the rheology of suspensions contributes to a better understanding of the underlying mechanisms of momentum and heat transfer process ( Telis-Romero et al. 1999 ; Nindo et al. 2005 ). Rheological properties are also important for the design of related processing systems, including filling in bottles/cans and appropriate piping arrangements ( Steffe 1992 ; Bhattacharya 1999 ). Krokida et al. (2001 ) recently assembled additional data on rheological properties of fruit and vegetable puree. Limited information is available in the literature on the rheological characteristics of herb purees. Herbal purees vary widely in their rheological characteristics and it is necessary to investigate each product separately. Results of this study would be useful in the quality control and design of processing equipment for processing coriander- and mint-based products. [ABSTRACT FROM AUTHOR]