Abstract
Abstract-The effects of solvent-to-feed (S) and temperature (T) on the kinetics and thermodynamics of the microwave assisted extraction (MAE) of flavonoids from dried fruits of Phyllanthus emblica using water as solvent have been studied. The flavonoid concentration - time data was analyzed using second order and diffusion models. Both the temperature and solvent-to-feed ratio influenced the initial extraction rate and equilibrium concentration. Biot numbers were found to be greater than 50, implying that the internal mass transfer was the rate controlling step in MAE. The composition of extracts obtained using MAE and conventional extraction was similar. However, the effective diffusion coefficients were doubled in MAE when compared to conventional extraction. An empirical correlation was developed to predict the kinetics of MAE as a function of solvent-to-feed ratio and temperature. The study will be of interest to food and pharmaceutical industries.
Highlights
Flavonoids and other polyphenols are effective antioxidants and free radical scavengers (Garcia-Castello et al, 2015), thereby evincing immense interest among the scientific community
In Eq (1), Ct is the concentration of flavonoids at any time t, Cs is the equilibrium concentration of flavonoids and k is the second order rate constant
No degradation of flavonoids was expected during microwave assisted extraction (MAE) under the present experimental conditions, as flavonoid degradation is reported to begin at a temperature greater than 110 oC (Xiao et al, 2008)
Summary
Flavonoids and other polyphenols are effective antioxidants and free radical scavengers (Garcia-Castello et al, 2015), thereby evincing immense interest among the scientific community. These are secondary plant metabolites that stimulate toxicological or pharmacological effects when consumed (Bernhoft, 2010). The fruits of P. emblica are highly nutritive, being rich sources of vitamin ‘C’ and superoxide dismutase with extensive medicinal uses. P. emblica fruits are used as laxative, acidulant and diuretic (Gowri et al, 2001). The fruits of P. emblica are highly perishable and dehydration of fruits for preservation is essential. Dried fruits of P. emblica are one of the constituents of the Ayurvedic medicinal preparation Triphala, the other being fruits of Terminalia chebula and Terminalia bellerica (Krishnamachary et al, 2012)
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