Optimization and Evaluation of phenolic compounds and their antioxidant activity from coffee beans.

Solvent extraction for estimation of polyphenols from green and roasted coffee beans (Coffea arabica) with methanol was optimized using response surface methodology, central composite design. Graphical optimization was carried out to find out experimental conditions that yield maximum polyphenol extraction and antioxidant activity. Results showed that significant factor affecting polyphenol extraction from green coffee beans was methanol concentration and time of extraction in roasted coffee beans. Average maximum polyphenol content extractable was 55 mg Gallic Acid Equivalence / g for green and 72 mg Gallic Acid Equivalence/ g for roasted coffee beans. Roasted beans were found to have higher polyphenolic content than green coffee beans and a positive nonlinear relationship was observed between polyphenol content and radical scavenging activity in both the cases. Also, extraction kinetics with respect to time was studied at their respective optimized conditions and stability of antioxidant compounds was compared. Initially, similar extraction pattern was observed in both types after which they traced different paths. Extraction of polyphenols from green beans showed continuously increasing polyphenol content and remained constant after attaining peak. Whereas, roasted coffee beans attained peak extraction within a few hours after which it drifted to a falling course showing formation of less stable and volatile phenolic compounds during roasting. Thus conditions for ideal spectrometric quantification of polyphenols using methanol as solvent was optimized for coffee beans.