Effect of microwave-assisted extraction on the release of polyphenols from ginger (Zingiber officinale).

The significance of different variables viz. temperature, time and solvent at constant power in microwaveassisted
extraction (MAE) process of ginger was studied and compared with conventional method. Aqueous
ethanol (50%) provided higher yields of extract as well as the highest release of total polyphenols
(TPP) than alcoholic solvents. The reason could be the high dielectric constant of aqueous ethanol as
compared to alcohols. Microwave heating being a volumetric process, an exposure time of 1 min was
found to be sufficient. The better penetration of microwaves and greater solubility at higher temperature
resulted in higher yield of TPP and [6]-gingerol. The resultant extract showed higher radical scavenging
activity (RSA) values. Thus, MAE allowed higher recoveries compared to conventional extraction process,
with improvement in the quantity and quality of extract in very short period of time.